The Potato Manifesto - Part 2/2: The Sweet Potato, Is It More Than Just the "En Vogue Tuber of the Year"?

Image 1: A mixer like this would be one of the best choices to turn your healthy low-GI sweet (or regular) potato into a high GI "nightmare".

If you've read yesterday's first part of the Potato Manifesto, you should by now be aware that the common notion of the pro-diabetic high-glycemic regular potato is another of the numerous black-or-white nutrition myths that do not become right, no matter how many bloggers and forum posters reiterate them. In today's second part of the series I will try to elucidate, whether the sweet potato, of which I would venture to say that she is the "en vogue tuber of the year", is not still the "safer starch alternative". So bear with me while I am using my scientific peeling knife to check whether there is a bitter truth hidden beneath skin of the sweet potatoes ;-)

Come on sweety, show me what's beneath your skin!

Now, if we take a look at the literature, a review of the glycemic index of 33 commonly available foodstuffs from the 1990s lists sweet potatoes with a glycemic index of 49 as #17 (with #1 peanuts and a GI of 11 and #32 cornflakes and a GI of 83 as the "extremes"; Nishimune. 1991). It is "outperformed by spaghetti (GI 47) and closely followed by Buckwheat, Yam (both GI 51) and you guessed it the good old "regular" potato, to which Takahiro Nishirnune and his colleagues assign a GI of 54, which - as you should know from yesterday's installment of the Potato Manifesto is nothing but an average on a scale that ranges from 10 to 110!

Figure 1: Difference in plasma glucose concentrations (expressed as the increase due to the "high GI" normal potato vs. the "low GI" sweet potato) in response to the ingestion of 50g of carbohydrates in form of bush potato or regular potato in 7 Aborigines and 7 Caucasians (data adapted Thorburn. 1986)

A brief note on the fallacy of common arguments for "traditional diets" (=sweet potato diets): I recently started listening to archived episodes of Jimmy Moore's Living La Vida Low Carb show and encountered time and again the 99% nonsensical argumentation that the XYZ thrived on whatever diet and that by just mimicking their diet(s), we would thrive, as well. To me this is like saying: "Look, the Panda bears thrive on a 100% bamboo diet! So, the ice-bears in our zoo should get along pretty well, if we stopped feeding them meat." Now, this is obviously a provocative comparison, but if I look at myself and then look at an Aborigine, the difference may not be as significant as the one between panda and ice-bear and yet, according to the results of a 1986 study by Anne W. Thorburn et al. (Thorburn. 1986) our glucose responses to the ingestion of 50g of carbohydrates from either the sweet-potato'esque bush potato and a "normal" western potato would be completely different (cf. figure 1). While the poor Aborigine would encounter the typical blood sugar ups and downs that are so characteristic for the ingestion of "high GI" carbs, my body would probably not care whether I eat the 100% paleo bush potato or its readily available, cheap cousin. The futility of common "neo-paleolithic" reasoning aside, this example also shows that genetic individualities are another major determinant of the glycemic index.

Three yeas later, in 1994, Thomas Wolever and his colleagues from the University of Toronto tested the glucose response of diabetic patient to 102 complex carbohydrate foods (Wolever. 1994). "Complex", in this case, indicates that they tested combinations of foods like they could appear on someone's dinner table and lo and behold, the "low GI" sweet potato took a close second to the "high GI" boiled white potato, when the both were boiled and served to 16 diabetic patients along with tomatoes. The 1 GI point difference between sweet and white potato (60 vs. 59) is yet well within the statistical margin.

Identical glycemic index, but differing free sugar compositions

Although, I hope that I should by now have convinced you that the glucose response is no convincing argument in favor of the sweet potato. I am even convinced that, if people abused their sweet potatoes in similar ways as their "regular" potatoes, i.e. mashed, fried, pureed, powdered and instantized it, we would soon see the (contemporarily) sexier sister of the regular potato on the list of "foods to avoid if you want to lose wait or just live a long and healthy life". Nevertheless, taste and name of the sweet potato, leave no doubt that there must be a sugary difference between her and her white brethren.

Figure 2: Free sugar composition (in mg/g) of 16 "regular" and 3 sweet potatoes cultivars (comparison based on data from Zhu. 2011 and Dincer. 2011)

And in fact, as my juxtaposition of data from a 2010 study on the relation between amino acid and sugar content of commercially available regular potatoes and its effect on the formation of acrylamite during heating (Zhu. 2011) and data from the previously mentioned (cf. Part 1) study by Cuneyt Dincer and his (or her) colleagues from the Akdeniz University in Ankara, Turkey (Dincer. 2011) shows (cf. figure 2), there is a non-negligable difference in the amount and composition of "free sugars" (vs. sugars in the form of starch). Although I am not 100% about the exact nature of the exotic Chinese potatoes, it is quite obvious that, despite large varieties in the absolute and relative sugar content of "regular" potatoes, the "classic" potato has a lower absolute free sugar content and contains more fructose and glucose than her sweet sister, 90% of the free sugar content of which is plain table sugar (=sucrose = glucose + fructose).

Figure 3: Mean free sugar composition (in mg/g) of fresh "regular" and sweet potatoes (comparison based on data from Zhu. 2011 and Dincer. 2011)

This "sugary" pattern does yet broaden, when you expose the sweet potato to heat in the form of either boiling or baking (cf. figure 4). In that, the cultivar-dependent slight reductions in glucose and fructose carry little weight compared to the sudden appearance of significant amounts of maltose, which had been beyond the detection before the sweet potatoes were boiled or baked (cf. figure 4).

Figure 4: Free sugar content (mg/g dry weight) of fresh and cooked sweet potatoes (data adapted from Dincer. 2011)

From a chemical perspective, the latter is not really surprising and its formation in response to heat treatment has been reported as early as 1923, when H.C. Gore published a paper in the Journal of Industrial and Engineering Chemistry (Gore. 1923), in which he makes the important observation that the formation of sugars from starch takes place within the first minutes of heating:

The  raw  potatoes  contained  0.34  per cent of  reducing  sugar calculated as maltose, the  cubes  cooked for  5  minutes in boiling water contained 8.32 per cent, and the cubes cooked for 1  hour,  7.82 per  cent.  Thus,  no sugar formation  occurred  at the  boiling point.

In view of this immediate heat-induced increase in the high GI free sugars, maltose (maltose has a ~10% higher GI than glucose), it should not surprise you that a study that was conducted by Jamaican scientists (Bahado-Singh. 2011), only a few months ago, found statistically significant increases in glycemic index and the area under the incremental glucose curve after boiling, frying, baking or roasting 10 sweet potato cultivars, which are commonly consumed in Jamaica (cf. figure 5):

Figure 5: Glycemic indices and glucose AUC of 10 common Jamaican sweet potato cultivars after boiling, frying, baking and roasting (data adapted from Bahado-Singh. 2011)

If we disregard the differences between the 10 cultivars and focus on the overall pattern, it is quite obvious that on the "less to worst thing you can do with your sweet potatoes if you are concerned about GI"-scale boiling is at the most benign end of the continuum, while baking and roasting compete for the position at the other end - a pattern, those of you who have already read Part 1 of the Potato Manifesto should be familiar with: Contrary to common believe new boiled (regular / sweet) potatoes are in fact a low GI food. In our kitchen (and even more so in the industrial processing machinery of the food industry), where the harmless tubers are mashed, pureed, dried, instantized, fried, baked, roasted etc., both, regular, as well as sweet potatoes do yet acquire at least some resemblance to the "pro-diabetic frankenfood", as which they have gotten labeled within the blogosphere, all along.

Figure 5: Comparison of regular and sweet potato glycemic indices after boiling, frying, baking and roasting.

If we now take a final look at the comparison of the average GI (figure 6 is based on data from both installments of the Potato Manifesto) of regular and sweet potatoes after boiling, frying, baking and roasting, it seems as if the main differences were that on average the regular potato has a slightly higher baseline GI (I do not need to remind you that according to Soh. 1999 boiled Desiree potatoes have a GI of 10!, do I?) and tends to be more resistant to heat-induced deteriorations in her starch / free sugar composition.

So, are boiled sweet and baked and roasted regular potatoes the way to go?

In view of the fact that probably 99% of the average and maybe 70% of the health conscious consumers don't even know the name of the potato cultivar they are using, let alone their age, storage temperature, the amount of phosphate in the soil on which it was grown, and all the other countless variables that have an impact on the "basal" GI of a potato, I honestly doubt that switching from one of the waxier, new regular potatoes (low basal GI) to a random (I mean, how many sweet potato cultivars are available at your grocery store?) sweet potato cultivar, would make you healthier, help you lose weight or offer any other GI-related benefits.

Image 2: Tapioca, another purpoted "health food" with a surprisingly high glycemic index GI of 84

Just as an aside, the Wolever study also examined the glucose response to another of the funky foods that are resurfacing on the Internet as "health foods", these days: Tapioca - also known as cassava, manioc, aipim, bitter-cassava, boba, mandioca, macaxeira, manioca, tapioca plant, yuca. With a GI of 84 it easily outperforms, corn chips (GI 76) and even waffles (GI 79).

Note: Wherever this was necessary I converted GIs that were given with white bread as a reference to the glucose as a reference.

Whether you could benefit from the (again, on average and in this case specifically referring to the white variety of the regular potato) higher beta-carotene and vitamin C content of sweet potatoes would depend on the rest of your diet. If the latter is "99% paleo" ;-), the likelihood that you would not get enough of these antioxidants is close to zero and it should thusly not really make a difference whether you go for the "paleo-" or the "neolithic" potato, as long as you don't (over-)process her into another of the innumerable frankenfoods the average member of the neolithic convenience society is so fond of.

The Potato Manifesto - Part 1/2: A (Re-)Evaluation of the Contemporary Discrimination of "the" Ordinary Potato

Image 1: The grunty regular (left) and the cute sweet potato (left), which one would you commit your health to? (img. menshealth.co.uk)

This is a blogpost, which eventually turned out to be the first part of a series, is a post with a history, a rather complex one, to be precise. It is rooted (not tubered ;-) in my amazement over the contemporary craving for sweet potatoes within the ever-growing neo-paleolithic community on the Internet and was sparked by the recent publication of a study on sweet potatoes, I stumbled upon on my daily tours of the most recent scientific literature. To make long story short, instead of immediately summarizing the data, drawing some graphs and commenting on the real-world implications of this study, I decided to use the holiday to descend into the archives and take a closer look at what science has to say on the bitter truth about the grunty regular and the starchy promises of cute sweet potato (cf. image 1 ;-)...

When wheat was devils excrement, would regular potatoes then be his horns?

According to the official obesity statistics of the European Union, British women are the fattest in Europe (Eurostat. 2011): 23.9% were classified as being obese (BMI > 30) in the year 2008 to 2009. This certainly raises the not altogether serious question, whether the British obesity problem (the obesity rate among the men was 22.1% and thusly topped only be the Maltese with 24.7%) is due to the fried fish or the fried (regular) potatoes in the unofficial British national dish, fish & chips.

Image 2: Obese British woman's rear view (img. BBC.co.uk)

A note to my dear American friends: Don't crow too soon, the obesity rate in the US tops the one in the UK by more than just a margin. According to a 2010 paper by Flegal et al. that was published in the Journal of the American Medical Association, the estimated obesity rate in the US amounts to 35.5% among the women and 32.2% among the men (Flegal. 2010). And a constantly increasing percantage (currently 4.7%) of the American population is already "extremely obese" and has a BMI > 40! Just to put that into perspective. A man or woman with a BMI beyond 40 and a height of 5 foot and 7 inches (170cm) would weigh at least (!) 254.85lbs (115.6kg) - this is already "Kig-Size Homer"-territory (cf. Intermittent Thoughts).

If we follow the current dietary paradigms and ignore the frying procedure, the answer to this question does not appear to be very difficult. I mean, when wheat was devil's excrement, then regular potatoes would be his horns or even nastier body parts, I do not want to mention here... and though a reasonable explanation for the widespread vilification of potatoes still escapes me, the contemporary nutritional paradigm within the health and nutrition blogosphere suggests that regular white potatoes have an awfully high glycemic index, will spike your blood sugar levels and have your neolithic body pump out tons of insulin - even if the rest of your diet is 99% paleo, as many of the listeners of Robb Wolf's podcast like to describe the way they are eating after having read his (widely read, yet controversial - esp. wrt to starches / carbs, fish oil and a few other topics) book ;-)

Figure 1: Names and characteristics of eight common potato cultivars in the British diet (left) and experimentally evaluated area under the glucose curve and glycemic indices (right; data based on Henry. 2005)

If we take a look at the data in figure 1, which shows both the incremental area under the glucose curve (AUC) and the GI of eight commercially available and commonly consumed British potato cultivars, it should however be quite obvious that the concept of the bad high-GI regular potato is about as misguided as the racist or religious prejudices some of our fellow human beings are still harboring against other members of the human race. With glycemic indices that range from 56 for the "waxy" Marfona to 94 for the "firm" Maris Peer, the "bad" regular potatoes cover the exact same GI range as their "healthy" sweet cousins (come back tomorrow for Part II of this series with more information on sweet potatoes).

Cultivar, processing, serving temperature and more have profound influences on the GI

The type  (=cultivar) of the (classic) potato, is yet neither the only, nor the most important determinant of the glycemic index of a potato meal. The processing method and, to my own surprise, even the food temperature have considerable influence on the glucose response to otherwise identical test meals, as well:

Figure 2: Incremental areas under the curve (AUC) and glycemic index values for 50 g available carbohydrate portions of white bread and seven potato meals tested in a cohort of 12 healthy subjects (data adapted from Fernandes. 2005)

On the left = "better than white bread"-side of figure 2, we have cold, boiled red potatoes (GI 56.2) and, surprise, frensh fries (GI 63.6) and roasted Californian white potatoes  (GI 72.3, but lower AUC than white bread). On the right = "worse than white bread"-side, instant mashed potatoes (GI 87.7) and the hot variety of the "low GI" red potatoes (GI 89.4) are competing for the red lantern.

With regard to the unexpected differences between cold and hot red potatoes, it is important to note that the results of a 2011 study by Kinnear et al. confirm that the latter is not an artifact of the Fernandes study. In their trial, the scientists from the University of Toronto found an average GI reduction of -37% (mean GI for the tested cultivars ~47), when the freshly boiled potatoes were refrigerated at 4°C for 24–28h before they were served to the 10 healthy study participants (Kinnear. 2011). As far as the reasons for this temperature-dependence of the glycemic index is concerned, Kinnear et al. speculate that it is an effect "due to starch retrogradation", which is a process that takes place in gelatinized starch, when the amylose and amylopectin chains realign themselves and thusly causes the liquid to gel. This is quite interesting, as it stands in line with the low GI of the Marfona potato (cf. figure 1), the texture of which is described as "waxy". The long-established relation of the phosphate content and the degree of starch gelatinization (and thusly digestibility and GI), on the other hand, could explain difference between crops and differences between identical crops grown on soil with different phosphate contents.

Figure 3: Areas under the glucose curves (AUC) in 32 healthy volunteers to 50g carbohydrates from mashed potatoes with or without 10g fructose administered 0, 30 or 60min before the meal. Measure by Accu Check finger-prick glucometer and YSI glucose oxidase analyzer (data adapted from Heacock. 2002)

Did you know that fructose, of all, is able to reduce the postprandial increase in serum glucose in nondiabetic adults (mean age: 26)? In their 2002 study, Patricia M. Heacock and her colleagues were able to show that pre-ingestion of 10g of fructose 60min and 30min before the ingestion of a 50g carbohydrate meal (from potatoes) reduced the area under the glucose curve (glucose AUC; cf. figure 3) by 25% and 27%, respectively (Heacock. 2002). The immediate co-administration of 10g of fructose with the potato meal (figure 3, 0 min), on the other, did not induce any statistically significant changes in the glucose AUC of the 13 male and 19 female study participants whose blood glucose levels were measured by finger-prick capillary blood (Accu Check) and glucose oxidase analyzers (YSI).

Furthermore, a 1999 study by Soh and Brand-Miller from the University of Sidney (Soh. 1999) shows that the real-world glucose responses of different individuals to differently processed and stored potato cultivars cover an even broader spectrum (especially on the low GI side) than the results of the previously cited studies suggested. The GI values, the Australian scientists calculated based on the glucose response to a 50g carbohydrate portion of eight different potato meals (three varieties, four cooking methods, two states of maturity) differed by as much as +/- 55pts, with canned new potatoes (GI 65) at the upper and boiled Desiree potatoes (GI 10) at the very lower end of the spectrum. And as if things were not complicated enough, already, Soh and Brand-Miller also introduce yet another variable into the equation - the size of the tuber, which showed a statistically significant correlation with the glucose response of the study 10 healthy participants (correlation between GI and tuber size: r=0.83, p < 0.05).

Black-and-white thinking and ineradicable prejudices

If we base our argumentation solely on the glycemic index, which is in fact the main argument that is brought forward against "regular" potatoes in the public debate, it is quite clear that the poor (regular) potato is another victim of the human propensity to black-and-white thinking and the public's stubborn adherence to convential nutritional wisdom. With reference to the "unjustified generalization" that "all potatoes have a high glycemic index", Anette E. Buyken and Anja Kroke, two researchers from the Research Institute of Child Nutrition in Dortmund, Germany, write in their letter to the editor of the British Journal of Nutrition (Buyken. 2005):

Figure 4: GI values (glucose reference) for potatoes by different cooking methods; the horizontal bars indicate the minimal and maximal glycemic index; the dotted vertical lines mark the conventionally accepted  "low GI" <55 (left) and "high GI" >70 (right) cut-off points (the figure was taken directly from Buyken. 2005)

[...] as with all GI data, the GI values of potatoes may depend on cooking method, processing, variety and the composition of the meal. This fact deserves attention since mashed potatoes, French fries, baked potatoes and potatoes cooked in a microwave are characterised by GI values mostly exceeding the upper limit for a high GI value of 70; whereas conventionally boiled potatoes appear to have a GI value on average below 70. The values of conventionally boiled potatoes do vary considerably though, so it may also be that some potato varieties have an inherently low GI what-ever the cooking method (Najjar. 2004; Fernandes. 2005). In this context, it should be considered that most currently available GI values are based on mature potato varieties (Ontario, Prince Edward Island, Desiree, Pontiac, Sebago). The starch of more mature potatoes is, however, easier to digest, presumably due to increased amylopectin branching and hence lower resistance to gelatinisation, which in turn results in a higher GI (Soh. 1999).

Buyken and Kroke support their argument by the means of an illustration of the broad range of the glycemic responses (and respective GI) of study participants to 46 different potato meals (cf. figure 4) and emphasize that there are significant differences in both the preferred potato cultivars, as well as the respective cooking / processing methods between European and US customers. While the former "prefer potato varieties characterised by a lower GI", the prevailing potato varieties in the US are mature and exhibit significantly higher glycemic indices. This trend toward higher glycemic indices in US potato meals is reinforced by the average American's preference to fry, bake, mash, roast or microwave his potatoes, so that it would  be "thoughtless" for any European, or American who selects less mature, low GI cultivars and refrains from frying, baking, mashing, roasting or microwaving his potatoes to follow the grossly over-generalized recommendation to eat less potatoes.

Ok, not all regular potatoes are made equal, but sweet potatoes are still king, right?

Against the background that my grand father who lived a 100% healthy, diabetes-free life into his late 90s, competed in track and fields and swam laps until about 6 months before he died, had regular potatoes with every dinner, I may be somewhat biased as far as the "bad potatoes" are concerned. This does yet not compromise the value of the rational arguments and scientific evidence against the unjust and, above all, over-generalized vilification of regular potatoes I have brought forward in this first installment of the Potato Manifesto. If you are interested in how the "holy" sweet potato which is currently hailed as the savior of the neo-paleolithic race compares, come back tomorrow for Part II of the Potato Manifesto ;-)

The Starch Satiety Shootout: Potatoes, Baked or Mashed, Pasta, Brown Rice or Even White Bread? What's the Best After a 12h Fast? Plus: Science Round-Up Preview!

Pasta! From a satiety perspective even white bread would be a better choice for breakfast.

It's one of those Thursday's where I am alone here at the SuppVersity - no Adelfo Cerame Jr. guest lecture today. But don't worry, there will not only be another guest post next Thursday, but both, today's SuppVersity post, which is actually related to Adelfo's "Carbophobia" post from last week, as well as the SuppVersity Science Round-Up  with Carl Lanore (live at 1PM EST on the Super Human Radio Network), will compensate at least somewhat for Adelfo's absence.

Apropos Science Round-Up, I am absolutely not sure where today's show will be heading to, but I can tell you that by now it looks as if we would start out with a very recent study on the leucine <> leptin connection and it's role in getting big and ripped.

It stands to reason that the big "L"s are not going to get the job done without some sort of workout, we will then segue into the acute hormonal effects of doing cardio before vs. after a workout - something I suppose many of you who have listened to the last installment and read the follow-ups (the Seconds and the post on PGC-1 alpha-4), here at the SuppVersity, will be intrigued to hear and something on which I want to provide a little more background information with respect to the role of fasting, overall energy intake, glyogen depletion, stress and a couple of other things that will primarily effect your luteinizing hormone levels and are thus equally important for male and female SuppVersity students.

I am honestly not sure how much time will be left, afterwards, but either live at 1PM EST, or as part of tomorrows "Seconds" you will also get the chance to learn something about the little known link between nicotine (as in cigarettes) and brain aromatase, the muscle building effects of exercise induced nNOS and the certainly not advisable, but probably likewise anabolic effects of capsaicin injections. And while there is more on the list, I guess this is enough for a preview... unless you were waiting for me to mention the endocrine disrupting effects of bottled water? No!? Well, then let's finally get to the actual post ;-)

Judging carbohydrates by their GI is like adopting another man's prejudice

As I already mentioned today's post is in a way an indirect follow up on Adelfo's confession that his love-and-hate affair with carbohydrates turned into a true friendship now. I mean starches are carbs and though Adelfo explicitly said that he says a place (in moderation) for all of them in his diet, it would be nice to know a little more about the differences between the dreaded potatoes, of which I have argued before that it is in your own hands whether they will (French fries, meshed potatoes, puree, etc.; "The Potato Manifesto") turn into a problem, or not, the demonized white bread and the "healthy" - since organic and brown - starch from pasta and rice.

I guess Allan Geliebter Michelle, I.-Ching Lee, Mariane Abdillahi and James Jones from the New York Obesity Nutrition Research Center at the St. Luke’s-Roosevelt Hospital Center that's part of the Columbia University College of Physicians and Surgeons in New York, when they devised the experimental procedures for their latest study (Geliebter. 2012). And in fact their approach to the problem appears to be pretty down to earth. Instead of just measuring insulin, glucose and what-not - we have had other scientists do that before - they simply fed their twelve healthy normal-weight participants (6 male, 6 female; mean age 25.6 years,  mean BMI 22.4kg/m², mean percent body fat 19.0%) who were recruited from the Columbia University community equienergetic portions (240kcal) of starch-rich side dishes:

• baked potato, no skin - nutrient composition as
• mashed potato, instant - Betty Crocker Idaho potato buds
• brown rice - Carolina natural whole grain brown rice
• pasta - Bionature organic pasta
• white bread - Wonder Classic Giant*

As the (*) indicates, the white bread was in there mainly as a GI standard (you usually supply GI values w/ reference to either glucose or white bread) and in order to make sure that it had it's 50g of carbs, just like all the other meals, the scientists needed so much that the overall caloric value of this "standard" meal was 33kcal higher (keep that in mind, thats ~12.5% and could therefore very well make a difference). In order to exclude any confounding variables, the water content (400g) and salt content were likewise standardized - both were added if necessary.

Pasta, rice and potatoes for breakfast?

In know, its not realistic that you have only pasta, rice, potatoes or white bread ... hold on, I know a couple of people in fact a large amount of my students eats nothing but white bread right from the baker for breakfast in their first lecture of the day :-( So it's not that unrealistic: At least we could ask ourselves would they be better off, if they ate potatoes, pasta or rice as their first meal after a 12h overnight fast, when maximal satiety is what we are looking for?

Figure 1: Hunger ratings and desire to eat from 10min before to 120min after the breakfast (Geliebter. 2012)

Well let's see, what do we have here? First off, one thing that's not in any of the graphs is the statistically significant gender bias, with the women experienced greater fullness across the test meals than men (p < 0.01). As far as the rest is concerned, the ...

• AUC of the appetite ratings from 10 minutes before to 120min after the ingestion of the meal did not differ, and still there was a...
• lower ‘desire to eat’ AUC following bakedpotato compared to pasta (p = 0.027) and brown rice (p = 0.004) and a much less significant advantage for rice over pasta (p = 0.041);
• changes in fullness, however, did not differ between test meals (not shown in figure 1)

So, obviously the baked potato, which was incidentally the only food that had no nutrition label (all the rest was packaged branded and labeled), was the subjectively most satiating starch source, followed by rice and trailed by the mashed potatoe and the distant (given the overall difference) "healthy" pasta.

So, to get back to my research question, whether my real students (not you, but those at the University), would be better off eating another bland starch instead of their buns, the answer would be yes - in the long run, both brown rice and baked potatoes would qualify. 

Potato-ish insulin spikes and low GI white bread

What is interesting though, is that the spike in the "How much food could you eat now?" graph in figure 2 coincides with the early insulin spike in response to the potato meals. If you are into grazing like a cow, i.e. if you like to eat bazillions of small meals, all day long, potatoes may therefore be not your best choice.

Figure 2: Insulin after breakfast,estimation how much the participants believe the could eat and calculated GI values (based on the measured glucose response; Geliebter. 2012)

What could be downright surprising for some of you, I guess, is yet probably the fact that anyone adhering to a low GI diet, would actually have to copy my students and eat the white bread, which had the lowest GI of all the test meals ... but I guess this and the fact that pasta by far the least satiating of the 4 meals had an only 7.6% higher GI should be the nail to the real-world relevance of the glycemic index, anyway.

The non-significance of the glycemic index  was also evident during the following lunch, where the subjects were allowed to chose or simply eat both of an on an individual base already non-manageable amount of chicken or tuna salad with mayonnaise, celery, salt, and pepper that were served "in covered serving containers with openings on top to reduce visual feedback" (Geliebter. 2012) and bundled with six slices of wheat bread and six slices of seedless rye bread:

"The group mean IAUC glucose and GI using the white bread standard and adjusted for the glucose load standard are listed in table 2 . Mashed potato had the highest GI of the side dishes. The correlation between the group mean fullness AUC and the group mean GI was 0.59. The correlation between the group mean fullness AUC and the group mean lunch energy intake was –0.21. These corrrlations are not significant." (Geliebter. 2012)

Remember Peter Czerwinski, aka Furious Pete's 900g of protein in 3:30min binge (Furios Pete, 2010)? No? In that case the fact that whey is more insulinogenic than white bread is probably news to you, as well, after all, the video was part of the SuppVersity post discussing that.

So, if you intend to become friends with starches and other carbohydrates, just like Adelfo did, don't judge them by the GI value you've found in whatever online or print source. Don't fear potatoes and if you need something to count to satisfy your OCD tendencies, count total amount carbohydrates (not the rice crumbs), keep the simple sugars in check and match both of them to your personal preferences / needs.

The GI is not the "unit of food quality"

And if that's not enough counting for you, what about counting the nutritional labels on the stuff you buy? The less you have, the better your diet - after all, whole foods you buy at the farmer's market or wherever else you can still get non-industrialized real food, does not have nutritional labels ;-)

References:

• Geliebter A, Lee MI, Abdillahi M, Jones J. Satiety following Intake of Potatoes and Other Carbohydrate Test Meals. Ann Nutr Metab. 2012 Dec 4;62(1):37-43.

Is Hypoglycemia Obesogenic? Is the GI Totally Worthless? Is Mild, But Chronic Stress Behind the Diabesity Pandemic? Is Leptin Obesogenic? And How Do You Calculate the Energy Requirements of Diabetics?

One of the mistakes researchers and dieters make time and again, using the scale as their only guide

Since I had a couple of interesting, but not earth-shatteringly exciting studies on obesity, body weight gain, the GI, leptin and a couple of other things lying around, I thought I'd compile a brief potpourri for you to get you on par with the helplessness with which researchers are still facing the diabesity pandemic. So don't expect any of the one-size-fits-it-all solutions the scientists still appear to be looking for from any of the following items. What you may find, however, is some inspiration when you read between the lines or follow up on the suggested reads, I mention. And if that's not the case, you can still browse previous articles on fat loss or simply go to the gym and try the fat loss example routine from the SuppVersity "Step By Step Guide for Your Own Workout Routine" or simply go to be early to preserve your circadian rhythm.

• Going "Hypo" time and again will make you fat (McNay. 2012) -- Usually you think of hyogylcemia as a sign of a lack of energy, yet despite the fact that this may well be the case this very lack in energy has recently been shown to exert obesogenic effects in a rodent model.
  
  

  

  Often a picture says more than 1000 words: Normal (left) and repeatedly hypoglycemic rodents after 8 months of weekly insulin injections (McNay. 2012)

  The weekly injections Ewan C McNay and his colleagues administered to their rodents and the subsequent episodes of hypoglycemia lead to profound weight gain in the absence of diabetes, hyperphagia, changes in hypothalamic NPY or POMC mRNA expression and  the other usual suspects that could explain this phenomenon. The one thing that's left is therefore what the researchers call a "multi-faceted deficit in metabolic regulation" (McNay. 2012) - interestingly enough the 69.5% higher body weight at 12 months went hand in hand with the usual laziness (-25% activity) of people whose brains are starving in abundance (e.g. type II diabetics).
  
  What remains to be seen, though, is whether similar effects would occur in response to "regular" non-insulin induced hypoglycemia. In view of the easy with which crash dieters and people with roller-coaster blood glucose levels gain weight, it is yet not unlikely that it is actually the avoidance of (reactive) hypoglycemia and not so so much the prevention of hyperglycemia that makes low GI diets successful for weight maintenance (for weight loss the picture is more complicated, since this will require a energy deficit and that's a game changer).

• Dietary glycemic index and load are not associated with type II diabetes risk in 12,403 Europeans (Sluijs. 2012) -- Apropos GI, scientists from the University Medical Center in Utrecht did not find statistical significant correlations dietary glycemic index and/or glycemic load and the risk to develop type II diabetes in in a subcohort of the European Prospective Investigation into Cancer and Nutrition Study (n = 12,403 participants).
  
  Even when they compared participants in the highest and lowest quantiles, the increase in risk was only 5% and 7% for GI and GL respectively. Since this is by no means the first study that suggests that the still propagated concept of the beneficial health effects "low GI diets" is faulty, I would suggest you rather watch the actual food items, than their respective glycemic indexes if you intend to ward off obesity and diabetes. Potatoes for example may have a high GI (including sweet potatoes, by the way), but their high potassium and overall mineral content, as well as the mere fact that you can hardly eat the same amount of total carbohydrates you can easily annihilate, when you are eating pasta still makes them one of the best sources of starchy carbs you have (learn more in the Potato Manifesto, Part I & II).

• 

  Figure 1: There were no statistically significant difference in terms of weight gain or loss, but the 2-week re-feed had a greater impact on blood glucose and insulin levels in the high GI group (Lagerpusch. 2012)

  There is use for the GI on a bulk or after a diet, but only if you are concerned about insulin sensitivity (Lagerpusch. 2012) -- While the general value of the GI as a means to distinguish good from bad carbohydrate sources is certainly questionable, the recently published results from a study that was conducted at the Institute of Human Nutrition and Food Science, of the -Albrechts University in Kiel, Germany, does suggest that monitoring the GI of your diet and adding additional fiber to reduce the insulin response to your meals can come quite handy, in phases, where you are particularly prone to store body fat. On a bulk, for example, or even more so when you have been dieting and are trying to return to a normal caloric intake.
  
  According to the results Lagerpusch et al. present in the November issue of the British Journal of Nutrition even healthy young men who were subjected to a 3-week diet phase (-50% in caloric intake) and subsequent overfeeding (+50% in caloric intake) the subjects in the high GI study arm had a 135% higher increase in fasting insulin levels during the refeed than those in the low GI group. In view of the fact that the glucose clearance (measured in an oral glucose tolerance test) was identical, it is not only no wonder that the weight gain did not differ either (see figure 1), but also unlikely that we would see significant differences as far as the fat gains are concerned (the latter were unfortunately not measured in the study at hand). At the same time, longer hyper-caloric high GI diets are certainly a risk factor for both insulin resistance and obesity, so that you are probably still at lower risk with 65g instead of 27g of fibre per day and a mean GI of 40 vs. 74.
  
  If you are interested in the influence of different diets on weight gain and health during overfeeding, I suggest you check out the following two SuppVersity posts: "194 Bananas in Three Weeks" and "A Tale of Macro- and Micronutrient Modifications".

• 

  Figure 2: Chronic mild stress leads to an overactivation of the HTPA and subsequen metabolic dysregulations (Takahashi. 2012)

  Further evidence that chronic mild stress is to blame for the obesity pandemic (Takahashi. 2012) -- As researchers from the Tohoku University Graduate School of Medicine in Japan report in the latest issue of the  American Journal of Physiology - Endocrinology & Metabolism, the localized re-setting of the clock genes in the liver, yet not the hypothalamic suprachiasmatic nuculeus (SCN), of BALB/c mice in response to chronic mild stress exposure elevated and phase-shifted serum corticosterone levels (see figure 2).
  
  Takahashi et al. argue that the observed changes are indicative of an overactivation of the HPA axis, which induced disturbances in the rhythmic expressions of core clock genes, e.g. Clock, Npas2, Bmal1, Per1 and Cry1 in the liver and subsequently circadian patterns of glucose and lipid metabolism-related genes such as the proliferator activated receptor (PPAR) family which favor the storage and hamper the oxidation of fatty acids.
  
  If you want to learn more about clock genes and how you can modify them, (re-)read the SuppVersity Circadian Rhythm Series!

• Scientists develop improved formula to calculate the resting energy expenditure of diabetics (Ikeda. 2012) -- While I would hope that you don't belong to the group who would have to use the new and improved formula scientists from the Department of Diabetes and Clinical Nutrition at the Kyoto University in Japan have now proposed, you may have clients or relatives who could benefit from its high predictive validity (78% +/- 103kcal vs. 50% for Harris-Benedict; 38% for Oxford, 42% for Liuand 63% for Ganpule):
  
  
  What you should keep in mind though, is that this equation was tested on Japanese individuals. Since we know from other studies that there are certain metabolic differences between people with different ethnic backgrounds I would remain a "healthy skeptic" as far as the outcomes of this equation are concerned - the same obviously goes for any other equation, e.g. the ones for athletes I provided in part III of the Female Athlete Triad series.

• 

  If you are interested in ways to modulate your leptin levels that may facilitate weight gain, I suggest you take a look at my second "Carbs Past 6PM Won't Make You Fat" post.

  Leptin induced weight gain? 13% more body fat in 2 weeks, when it hits the wrong part of the brain (Harris. 2012) -- With the mixed results from intervention trials, the enthusiasm around leptin has abated over the past months, the general consensus is yet still that leptin and leptin resistance loom large in the metabolic dysregulation that's at the heart of the diabesity pandemic. Against that background, the results Ruth B.S: Harris presents in her latest paper in the American Journal of Physiology - Endocrinology & Metabolism are unquestionably surprising.
  
  When Harris injected twice the amount of leptin (0.6 µg leptin/day) that had previously been shown to decreased 24 food intake, body fat and lean tissue, when it was injected into the third ventricle of the hindbrain, into the fourth ventricle of her lab rats, the rodents gained an almost incredible amount of 13% body fat within only 2 weeks! And that in the absence of statistically significant change in daily food intake, suggests an "increase in efficiency of energy utilization" (Harris. 2012). Fortunately, further experiments showed that the pro-obesogenic effects of leptin in the 4th ventricle was antagonized when both the 3rd and the 4th ventricle were exposed to leptin. In this scenario the leptin exposure of the 4th ventricle did even protect the lean mass of the rodents from the negative effects the exclusive exposure of the 3rd ventricle had. Overall, the study is yet somewhat chaotic and a clearcut message aside from "look people things are even more complex than we already thought", is probably not going to contribute to a solution of the obesity dilemma in the near future. 

There are, as usual more news on Facebook, some of them, such as the relation between hypothyroidism during pregnancy and the diabetes risk of the offspring later in life, are even related to the topic at hand. And if that's nothing you are interested, you may want to read about ...

• the non-existent effects of coffee consumption before bed on the sleep quality of habitual coffee drinkers (read more),
• the problem with inaccurate vitamin D tests and the absence of a reliable and scientifically sound definition of "vitamin D deficiency" (read more), or
• the strength promoting in-vitro effects of sodium bicarbonate, or in other words, a rather alkaline milieu on muscular force production (read more)

... and if neither of those can satisfy your thirst for more information from the realms of exercise and nutrition sciences, you can still wait for the next serving of facebook news or tomorrow's SuppVersity article :-)


References:

• Harris RB. Leptin-induced increase in body fat content of rats. Am J Physiol Endocrinol Metab. 2012 Dec 4.
• Ikeda K, et al. A new equation to estimate basal energy expenditure of patients with diabetes. Clinical Nutrition. 2012 [article in press] 
• Lagerpusch M, Enderle J, Later W, Eggeling B, Pape D, Müller MJ, Bosy-Westphal A. Impact of glycaemic index and dietary fibre on insulin sensitivity during the refeeding phase of a weight cycle in young healthy men. Br J Nutr. 2012 Nov 28:1-11.
• McNay EC, Teske JA, Kotz CM, Dunn-Meynell A, Levin BE, McCrimmon RJ, Sherwin RS. Long-term, intermittent, insulin-induced hypoglycemia produces obesity without hyperphagia or insulin resistance: a model for weight gain with insulin therapy. Am J Physiol Endocrinol Metab. 2012 Nov 20.
• Sluijs I, Beulens JW, van der Schouw YT, van der A DL, Buckland G, Kuijsten A, Schulze MB, Amiano P, Ardanaz E, Balkau B, Boeing H, Gavrila D, Grote VA, Key TJ, Li K, Nilsson P, Overvad K, Palli D, Panico S, Quirós JR, Rolandsson O, Roswall N, Sacerdote C, Sánchez MJ, Sieri S, Slimani N, Spijkerman AM, Tjønneland A, Tumino R, Sharp SJ, Langenberg C, Feskens EJ, Forouhi NG, Riboli E, Wareham NJ; on behalf of the InterAct consortium. Dietary Glycemic Index, Glycemic Load, and Digestible Carbohydrate Intake Are Not Associated with Risk of Type 2 Diabetes in Eight European Countries. J Nutr. 2012 Nov 28.
• Takahashi K, Yamada T, Tsukita S, Kaneko K, Shirai Y, Munakata Y, Ishigaki Y, Imai J, Uno K, Hasegawa Y, Sawada S, Oka Y, Katagiri H. Chronic mild stress alters circadian expressions of molecular clock genes in the liver. Am J Physiol Endocrinol Metab. 2012 Dec 4.

Chicken, Rice, Veggies & Oil and How Their Effects on Your Insulin & Glucose Levels Are 50% Off Those You'd Expect Based on the Calculated Glycemic Index of This Meal

The power of GI calculations is limited and even with meals as simple as the one in the picture, the calculated glycemic index can be ~50% off!

As a SuppVersity reader you've repeatedly read about macronutrient interactions, such as the insulin boosting effects of whey protein or dietary fat, studies that investigate the effects of the individual ingredients of a complete meal on the glycemic response healthy men and women, however, are scarce. Against that background the results of a recent study from the Clinical Nutrition Research Centre at the Singapore Institute for Clinical Sciences are of particular interest. After all, the Lijun Sun et al. (2014) determined the effect of co-ingesting a high-protein food (breast chicken), a fat (ground nut oil), a leafy vegetable or all three on the glycaemic and insulinaemic responses of white rice in healthy adults and did thus produce results that could be practically relevant for all of us - more relevant than inaccurately calculated GIs.

Use sugar alternatives if you want to improve your blood glucose!

Unsatiating Truth About Sweeteners?

Will Artificial Sweeteners Spike Insulin?

Sweeteners & the Gut Microbiome Each is Diff.

Sweeter Than Your Tongue Allows!

Stevia, Much More Than Sweet?

Artif. Sweetened Foods Good, Not Bad for Fat Loss.

Before we get to the study results, though, let's briefly recap what the researchers actually did: Sun et al. recruited twelve healthy participants (six female and six male) by means of advertisements, flyers and personal communications.

"Before inclusion into the study, potential participants were briefed on all aspects of the experiment and were given the opportunity to ask questions. Following the securing of consent, a health assessment was performed which included anthropometric measurements and a health questionnaire (giving details of food allergies/intolerance, metabolic diseases, special dietary needs and smoking habits). Those who fulfilled all the inclusion criteria [body mass index 18.5–24.99 kg/m2; blood pressure (BP)—systolic BP between 110 and 120 mmHg and diastolic BP between 75 and 85 mmHg; age 21–50 years; fasting blood glucose, 4–6 mmol/L; not on prescription medication, non-smoking; no genetic or metabolic diseases) were enrolled into the study." (Sun. 2014)

In addition, the amount of regular physical activity was quantified and subjects who were partaking in competitive sports and endurance events were excluded. Eventually, the scientists ended up with a group of normal-weight men and women at the age of 21–34 years.

Table 1: Composition of the test meals, ACHO = available carbohydrates.
Nutritional data were obtained from the manufacturers (Sun. 2014).

The subjects visited the laboratory 5 times (plus a baseline testing with a glucose solution). On each of these testing sessions, which were separated by at least one week, the subjects arrived at the laboratory between 7:30 and 8:30 after an overnight fast and received one of the five test meals from Table 1, which contained 194 g white of plain white rice,  254 g of white rice with fat, 294 g of plain white rice with chicken breast, 314g of white rice with vegetable and 474g of white rice with fat, chicken and vegetable, respectively.

Ground nut oil? I guess most of you will know the oil that was used in the study at hand as "peanut oil" and it is - as you will probably know, as well - not exactly high in "holy" omega-3 fatty acids. Rather than that, peanut oil contains oleic acid (46.8% as olein), linoleic acid (33.4% as linolein), and palmitic acid (10.0% as palmitin), as well as small amounts of stearic acid, arachidic acid, arachidonic acid, behenic acid, lignoceric acid, but not a singly milligram of omega-3s.
The test or reference food was then given to consume within 15 min. Further blood samples for glucose and insulin analysis were taken for the subsequent 180 min (every 15 min in the first hour and every 30 min for the subsequent hours) - a procedure that yielded the following results.

Figure 1: Glucose levels expressed relative to the ingestion of 250g of glucose (Sun. 2014)

The values in Figure 1 are expressed relative to the glucose response to 250g of pure glucose, of which a brief glimpse at the data tells you that they produce higher peak and incremental area under the curve (iAUC, a measure for the glycemia over the whole testing period) levels than any of the meals. Statistical significant differences were yet observed only for rice with chicken breast, rice with vegetable, and rice with fat, chicken and vegetable - yet not for the plain rice and the rice + fat meal (the latter was to be expected based on the discussion in my previously referenced article "True or False? Adding Fat to A Carby Meal Lowers Insulin Response" | read more).

Significant differences for the insulin response were observed for the white rice + chicken meal, where the insulin response was significantly higher compared to the white rice only (+22%), as well as the rice with + vegetable meal, where the insulin response was significantly lower compared to the white rice only condition (-16%).

The combination of foods determines the GI of the meal

Based on the classic equation that's usually used to determine the glycemic index of a meal (Hätönen. 2011), Sun et al. calculated the predicted glycemic of the five test meals and compared it to the actual glycemic index (GI) that was calculated based on the measured glucose and insulin response of the subjects.

Figure 2: Predicted and measured glycemic index as well as measured insulinemic index of the meals (Sun. 2014)

As you can see in Figure 2, the comparison yields an unsurprising result. As it's usually the case, when simple equations are used to predict physiological effects, the real GI values were significantly different from the calculated ones and  - significantly lower, that is. Accordingly, the meal with the least impact on postprandial glycemia and a comparatively low insulinemic effect is the one containing rice, fat, chicken and veggies - in other words, the complete meal. 

Suggested Read: "Get Your Protein, Veggies & Fruits and Get Them Regularly: High(er) Meal Frequency (6 à Day) + High(er) Protein Diet Support Weight & Fat Loss on a Diet." | read more

Bottom line: While the importance of the glycemic index (GI) has long been totally overrated, there is accumulating evidence that high postprandial glucose levels are a significant contributor to increases in cardiovascular disease risk even in healthy individuals (Einarson. 2011; Mah. 2011). Against that background the results of this recent trial support my previous recommendation to consume balanced meals containing protein, fat and carbohydrates, instead of no-fat or no-carb meals.

In contrast to what the "paleo hypothesis" and the notion that our ancestors would not have collected some berries or boiled some rice to have it alongside the chicken they just caught would say, the contemporary scientific evidence indicates that we are well equipped to handle complex meals, as long as they don't contain exorbitant amounts of fat and carbohydrates.

One thing we should not forget, though, is that the 50% discrepancy between the calculated and real glycemic index of the "complex" test meal (four ingredients is not exactly "complex", actually) suggests that one of the reasons that many of the previous studies failed to detect a meaningful association between the (obviously calculated) GI of an individuals diet and his / her cardiovascular or diabetes risk may be that the data the scientists used was similarly inaccurate as the predicted glycemic indices of the test meal in the study at hand | Comment on Facebook!

References:

• Hätönen, Katja A., et al. "Protein and fat modify the glycaemic and insulinaemic responses to a mashed potato-based meal." British Journal of Nutrition 106.02 (2011): 248-253.
• Mah, Eunice, et al. "Postprandial hyperglycemia impairs vascular endothelial function in healthy men by inducing lipid peroxidation and increasing asymmetric dimethylarginine: arginine." The Journal of nutrition 141.11 (2011): 1961-1968. 
• Sun, Lijuan, et al. "Effect of chicken, fat and vegetable on glycaemia and insulinaemia to a white rice-based meal in healthy adults." European journal of nutrition (2014): 1-8.
• Wolever, T. M. S. "Is glycaemic index (GI) a valid measure of carbohydrate quality&quest." European journal of clinical nutrition 67.5 (2013): 522-531.

Macro Ratios & Glucose Management: Eating Lower GI Carbs and Higher Protein Alone is Less Effective in Blood Sugar Normalization Than You May Have Thought

Macronutrient ratios matters, but food quality does, too. And so do exercise, laziness, sleep, .... the list is endless, so can we be surprised that modulating GI and protein is not helping much?

We all "know" that going low(er) carb is good for your blood glucose management, right? Nice! So, we probably don't need studies like the Marleen A. van Baak's conducted only recently, right? I mean, carbs are bad! So why would we even be interested to hear how much the subjects of the Diogenes Study lost on one of four different diets with varying protein content and glycemic index? Or who would want to know what the subjects' 24-h glucose profiles on one out of four diets differing in carbohydrate content by 10 energy % and glycemic index by 20 units during three days. No one would like to know that, right!?

In view of the fact that you're still there, I suppose that I was wrong and you are interested in the effects of different marconutrient ratios and types of carbohydrates (low vs. high glycemic index) on weight loss and glucose management. Let's take a closer look at the design of the Diogenes Trial (learn more), then.

Use alternatives to sugar sweetened beverages if you want to improve your blood glucose!

Unsatiating Truth About Sweeteners?

Will Artificial Sweeteners Spike Insulin?

Sweeteners & the Gut Microbiome Each is Diff.

Sweeter Than Your Tongue Allows!

Stevia, Much More Than Sweet?

Artif. Sweetened Foods Good, Not Bad for Fat Loss.

The Diogenes Study was a field study, in the course of which subjects were randomized into 5 different diets: lower protein (LP)/lower GI(LGI), higher protein (HP)/LGI, LP/higher GI (HGI),HP/HGI and a control diet according to national recommendations for a healthy diets.

• The intended difference in protein content of the LP and HP diets was 10%–12% of energy intake.
• The intended difference in glycemic index between the LGI and HGI diets was 15. 

All diets were reduced in fat (<30 energy%) to make room for significant differences in the CHO to PRO ratios. All subjects had to keep food diaries and monitor their glucose levels continuously.

Table 1: Examplary diet composition in the Diogenes Trial (van Baak. 2014)

As some of you will probably remember (I've written about the Diogenes Study and its results in the Facebook News, previously), the total amount of weight the subjects lost from the start of the Diogenes Study was 8.8 ± 8.4 kg. The subsequent weight regain since the start of the randomized diet intervention was 1.6 ± 7.3 kg, with no significant differences between the diet groups (in spite of a marginal advantage for those who kept eating a high(er) protein diet).

Lifestyle changes are more powerful than supplements: So don't forget that it's imperative to realize the lifestyle changes described in the first installment of the "Improve Your Glucose Sensitivity"-series. Otherwise the best you can hope to achieve with supplements (and drugs) is to slow the progression from insulin resistance to full-blown diabetes.

The analysis of the three-day dietary records showed the expected differences in carbohydrate content and glycemic index between the diet groups, but the differences were smaller than intended (a bummer in view of the fact that they were not large to begin with). Much in contrast to what our initially phrased prejudice would say, there were no significant differences in mean 24-h, daytime or nighttime glucose concentrations between the diet groups.

Table 2: Self-reported dietary macronutrient composition in the field study (a) and macronutrient
composition of the diet in the lab study (b) (van Baak. 2014)

Moreover, the absence of at least a deviation in standard deviations (SD) signifies that the lack of statistical significance is not due to extreme outliers who may not have adhered to their dietary prescription (macronutrient make-up / reported / see Table 2).

"Post hoctesting did not reveal differences between the LP/HGI diet and any of the other diets for the glucose parameters studied. Adjustment for BMI, HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) index, minutes of exercise performed by the subjects, total weight loss or weight regain did  not change this outcome (data not shown)." (Van Baak. 2014)

Still, in a relatively uncontrolled scenario like the one in the Diogenes Study it's always possible that someone cheated twice, i.e. he deviated from the diet and reported to have stuck to it to the literal "T". Against that background, the results of van Baak's three-day follow up in a very controlled scenario is all-the-more interesting.

Figure 1: Parameters of glucose homeostasis means (left) and standard deviations (right)
on the different diets in the lab study (van Baak. 2014)

It's a study in which we see the same non-significant effects of the macronutrient ratio on ability of the study participants to keep their glucose in check. With goodwill you could say that protein seems to buffer the glucose excursions, but with p-values of p >> 0.05, this effect is everything but statistically significant.

To find an effect that is statistical significant we do thus have to take a look at the continuous overlapping net glycemic action over 1 h periods (CONGA1) values over 24 h on the different diets in the lab study, where the high protein + low GI group finally shows the statistically significant advantage we've been waiting for all along (see Figure 2). Still, as the scientists point out, overall their data does not support the hypothesis that "glucose concentrations would be highest on the reference diet (LP/HGI) compared to all other diets and especially compared to the HP/LGI diet." (van Baak. 2014). As the author points out, the study did yet provide support for the hypothesis regarding glucose variability was found, since both 24-h and daytime variability of glucose concentrations were lower on the HP/LGI diet than on the LP/HGI diet.

Learn how to improve and maintain your insulin sensitivity in a previous article and the corresponding series about ways to improve your insulin sensitivity, naturally.

Bottom line: I am not sure what to make of this study, but I guess that the fact that the macronutrient manipulation had a relatively minor impact on the glucose levels of the overweight subjects confirms that "hitting your macros" is by far not all you've got to do if you want to get away from the road to diabesity | What's your take on this study - comment on Facebook!

That being said, there is no doubt that a high(er) protein, low(er) GI will make it much easier to return to the realms of the few non-pre-diabetics. In that, the effects will probably be even more profound if you increase the protein intake by more than 10% over the reference value of 0.8g/kg.

Doubling the protein intake, for example, would necessarily require a reduction in carbohydrate and fat intake of 3.2kcal/body weight. For a person who weighs 100kg that would be 320kcal and 80g of carbs or 40g of fat - with the former usually being the better idea for anyone who's still significantly overweight and not already eating less than 180g of carbs per day.

Reference:

• van Baak, Marleen. "24-Hour Glucose Profiles on Diets Varying in Protein Content and Glycemic Index." Nutrients 6 (2014):3050-3061