PUFA Increases Postprandial Thermogenesis in Healthy Premenopausal Women & Beyond - 14% Increase Over MUFA & SFA Sounds Huge, But Does it Matter?

Is there something to the good vs. bad fat shenanigan, after all?

Only recently scientists from the Texas Tech University report that a PUFA-rich high-fat meal led to a greater diet-induced thermogenesis in normal-weight premenopausal women compared with SFA- or MUFA-rich high-fat meals.

Reason enough to take a closer look at this and previous studies investigating the diet-induced thermogenic effects of PUFA-, MUFA- and SFA-rich meals and to conduct a reality check wrt to the question whether these differences actually matter - I mean, will you get and stay lean by upping your PUFA intake? Let's take a look!

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In the initially mentioned study, Hui C. Clevenger, Amanda L. Kozimor, Chad M. Paton and Jamie A. Cooper explored the effect of three HF meals enriched with different fatty acids (MUFAs, PUFAs or SFAs) on metabolism in premenopausal women of normal weight. In that, the metabolic parameters of interest included postprandial energy expenditure (EE), which is then used to calculate DIT, and substrate oxidation, which included respiratory exchange ratio (RER), fat oxidation and carbohydrate (CHO) oxidation.

Based on previous research in men of normal weight, the Texas Tech researchers hypothesized that the diet induced thermogenesis (DIT) and fat oxidation would be the highest after the PUFA- and MUFA-rich meals and lowest after the SFA-rich meal in premenopausal women - a result of which you already know that it was only partly confirmed.

Figure 1: Diet-induced thermogenesis and respiratory exchange rate (higher RER = lower fatty acid oxidation vs. higher CHO oxidation) in the 5h after the test meal (Clevenger. 2014)

The data in Figure 1 does after all tell you that the expected MUFA-induced increase in diet-induced thermogenesis did not occur. PUFAs, on the other hand did the job, Clevenger et al. expected them to do. They increased the DIT by an ostensibly whopping 14% over the DIT the scientists observed in response to the ingestion of the high MUFA and SFA liquid meals that had been prepared with the same base of 8 fl oz (237 ml) of chocolate Ensure(R) with soy lecithin and Nesquik (R, but contained different additional dietary fatty acids added depending on the treatment condition:

• 

  Table 1: Liquid meal nutrient composition
  breakdown (Clevenger. 2014).

  The PUFA-rich meal was ‘base’ plus sunflower oil and flaxseed oil, with 42% of total energy coming from PUFA.
   
• The MUFA-rich meal was ‘base’ plus canola oil and extra virgin olive oil, with 42% of total energy coming from MUFA.
  
  
• Finally, the SFA-rich meal was ‘base’ plus butter, coconut oil and palm oil, with 40% of total energy coming from SFA. 

As the data in Table 1 indicates, the nutrient profiles didn't differ much. The fatty acid composition, on the other hand did, with the SFA meal being the only one with measurable amounts of Butyric, Caprioc, Caprylic, Capric, Lauric, Myristic and Hepatedic acid. Fatty acids of which previous research indicate that they induces an obesity-linked proinflammatory gene expression profile in adipose tissue of subjects at risk of metabolic syndrome (van Dijk. 2009).

High MUFA diets, on the other hand, have been shown to potentiate the effects of weight loss in obese NIDDM patients (Low. 1996). They are the major group of fatty acids in the one oil, everyone appears to agree that it's health (Olive oil). And last but not least, even the allegedly unhealthy omega-6s have been shown in randomized controlled to reduce liver fat and modestly improve metabolic status, without weight loss, when compared to high saturated fat diets (Bjermo. 2012).

All of these effects / this evidence could potentially be more important than the increase postprandial thermogenesis in the study at hand - so the ultimate question is: Does DIT even matter?

Now, does this increase in DIT matter? Westerterpet et al. who found a negative correlation between body fat levels and the diet induced thermogenesis in their 2008 study (Westerterpet al. 2008), certainly believe it matters. If we look at the total extra diet-induced energy expenditure in 5h after the test-meal in the study at hand, on the other hand, I cannot but ask myself, whether those 1.4kcal can actually make a difference.

I am not sure what you think, but considering the fact that you can burn those 1.4 extra calories in less than one minute in the gym, it's hard to believe that the increased thermogenesis alone warrants the layman's conclusion that the study at hand would provide evidence for the superiority ot PUFAs over MUFAs and saturated fats ... what do you think?

References:

• Bjermo, Helena, et al. "Effects of n− 6 PUFAs compared with SFAs on liver fat, lipoproteins, and inflammation in abdominal obesity: a randomized controlled trial." The American journal of clinical nutrition 95.5 (2012): 1003-1012.
• Clevenger, Hui C., et al. "Acute effect of dietary fatty acid composition on postprandial metabolism in women." Experimental physiology (2014): expphysiol-2013.
• Westerterp, Klaas R., et al. "Dietary fat oxidation as a function of body fat." The American journal of clinical nutrition 87.1 (2008): 132-135.

MCT + Chili Make a Pretty HOT Pair: 50% Increase in Diet Induced Thermogenesis in Well-Controlled Human Trial

If you like chili oil, go for it, otherwise perform the reality check before ruining your taste-buds.

While the word "thermogenic" still carries much weight in the world of the average fitness maniac, SuppVersity readers like yourself should know better than to go crazy over rodent study #1021412 showing "potent thermogenic effects" when an extract from an exotic herb in Dr. Oz garden was administered once in an equivalent dosage that would require you to ingest the whole package of the corresponding "brand new, revolutionary" fat burner that's marketed by the said study.

Human study + no exotic herbs - so does it work?

Well with the study at hand, things are somewhat different. Firstly, the experiment Miriam E. Clegg, Mana Golsorkhi and C. Jeya Henry conducted was done with human, not rodent "subjects". Secondly, the "supplements" they used were no exotic herbs from Dr. Oz Garden or whatever remote region in the Himalaya they were simple MCT oil & Chilis - 20g of 30g of a hot chilli spice blend (Gourmet garden, Northampton, UK), to be precise the former and 30g of. And thirdly, the a +50% increase in diet induced thermogensis could actually make a difference - in the very long term and if you are using it on top of a energy restricted diet.

Figure 1: Macronutrient composition of the iso-caloric test meals; *due to the lower energy density of long-chain triglycerides, only 18.4 g of sunflower oil was used to match the energy content of the meals (Clegg. 2013)

In a randomized controlled fashion, the subjects, 7 healthy volunteers (6f 1m; 25.7±3.6 year;
1.69±0.09 m; 62.5±7.5 kg) who had reported fasted to the lag in the morning of the testing days, consumed a standardized English breakfast consisting of  consisting of an egg omelet, tomato, mushroom, sausage, bacon, toast and some "good old" orange juice.

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"The cooked breakfast was prepared with chilli and MCT oil, chilli and sunflower oil, bell pepper and sunflower or bell pepper and MCT oil added to the omelet.

Glucose was added to chopped bell pepper to give it a similar macronutrient and energy cost as the chilli mix. The chilli mix consisted of 60 % chilli (cayenne, habanero). The capsaicin content of the chilli blend was estimated about 2,000 ppm capsaicin (based on information provided by the manufacturers). According to this, the 30 g chilli blend added to breakfast meal was comparable to the amount of chilli used (30 g) in earlier studies to assess the effect of chilli on metabolic parameters." (Clegg. 2013)

The resting metabolic rate of the subjects had been deterimned before breakfast, while the diet induced thermogenesis (DIT) was quantified for 15 minutes they "broke their fast" (learn more about "breaking the fast" here) and then every 30 min within the following 6h.

Suggested read: "Are You Still Burning Calories or Already Losing Fat? Study Shows: 5x15 Min HIIT Reduce Body Fat & Improve Fitness Twice as Effectively as 5x40min of Classic Cardio" | read more

"The energy expenditure increased postprandially following all four breakfasts reaching a peak in the chilli–sunflower oil and pepper–sunflower oil at 1 h and at 2 h in the chilli– MCT oil and pepper–MCT oil, respectively. [...]

There were significant differences in total DIT and percentage DIT between the different breakfast meals (P=0.003). [...]

Chilli–MCT had the highest EE, and pepper–sunflower oil had the lowest. It was noted that the increased energy expenditure occurred between 2 and 6 h postprandially; analysis of these data alone substantiated the results above.

Interestingly, the rate of fatty acid oxidation did not vary significantly. Well, with one exception: The difference between the contribution of fats to the total energy expenditure was significantly different for the pepper–sunflower oil and pepper–MCT oil (P=0.032) trials. Similarly, the meal induced elevation in carbohydrate expenditure was more pronounced in the +MCT trials than in the + sunflower oil trials, but neither of these effects resulted in measurable differences in terms of satiety, hunger, fulness or prospective food consumption, which were all identical across the groups.

Real-world Significance and the Theory of Relativity

The same goes for symptoms of gastrointestinal distress, which is something that's actually a little surprising. After all, both MCTs and chili have been described as potential gut irritants in certain populations, yet none of the participants appeared to suffer more during the corresponding testing conditions.

Figure 2: Ratios are important, but total increases in energy expenditure of max. 12kcal are simply laughable (Clegg. 2013)

So, we do have a side-effect 50% increase in diet-induced thermogenesis? Awesome... well, you look at the absolute value of post-prandial energy "wasting" in response to the selection of the "right" oils and take into consideration that a previous study showed that the "fatty oxidation bonus" from MCTs vanish over time (learn more), it remains questionable, whether even these, allegedly pronounced increases in diet-induced thermogenesis will do anything.

---

Remember: "The only consistent finding among [fat loss trials on both ends of the low vs. high carb spectrum] is that adherence - the degree to which participants continued in the program or met program goals for diet and physical activity - was most strongly associated with weight loss." (Pagato. 2013)

Bottom line: Personally, I don't think it's worth to spice up your food with "MCT + chili" - unless, of course, you like it this way. If that's the case the extra 12kcal of energy expenditure are something I believe few of you will mind.

If, on the other hand, you are just telling yourself that you like your food with chili and MCTs, you should not be wondering that all your past weight loss efforts have sucked. If there is anything that really messes with weight loss success, it's not low postprandial thermogenesis, but not sticking to one's diet; and if the food you eat does not only contain less energy than you want, but also tastes like fiery crap, falling off the wagon and not achieving your fat loss goals is almost guaranteed; and if that happens your relatively large (~50%), but in absolute terms already irrelevant increase in daily energy expenditure is not going to help you.

References:

• Clegg ME, Golsorkhi M, Henry CJ. Combined medium-chain triglyceride and chilli feeding increases diet-induced thermogenesis in normal-weight humans. Eur J Nutr. 2013 Sep;52(6):1579-85.
• Pagato SL, Appelhans BM. A Call for an End to the Diet Debates. JAMA. 2013;310(7):687-688.

Grazin' Study Shows: Increased Eating Frequency Bad For Obese and Lean Men. Reduced Diet-Induced Thermogenesis and Blunted Lipolysis Could Promote Future Weight Gain

Grazing not allowed!

Usually, I don't do this in the introduction of an article, but in this case, it fits so nicely that I just can't resist to prepend todays SuppVersity article with a citation from the conclusion of a recent paper in Pyschology and Behavior, a journal of which I believe that it covers the true reasons of the obesity pandemic... but I am digressing, here's your quote (Allroit. 2014):

"Even if subjective and physiological data suggest a beneficial effect of frequent eating on appetite in obese men, no effect was demonstrated on energy intake. Moreover, the decrease in diet induced thermogenesis and lipolysis, reflected by NEFA profiles, could be deleterious on energy balance in the long run."

What? Grazing ain't good for me? But my doctor (Oz?) said so!

If you are still in the "I believe every word my doctor" says phase of your development as a free-thinking individual, it's probably a waste of time to read the rest of the article. If you have an open ear and eye for the scientific discoveries that have been made in 25 years that have been passed since the 5th edition of the by then already outdated textbook your doctor used during his studies were published, I'd suggest you take a look at the overview of the study design:

"[A]fter being included, the subjects had a first visit for a lunch at the experimental restaurant of Institut Paul Bocuse Research Centre (IPB). The aim of this first visit was to familiarize the subjects with the environment and the foods which would be used during the study.

During this visit, subjects were invited to the experimental restaurant at 12:00 and were asked to taste all of the food items offered at an individual buffet-type meal. A choice of classical hot and cold French food items with varied macronutrient compositions was offered. [...] Subjects were instructed to eat ad libitum. The mean rating of food items, measured on a 100 mm electronic visual analog scale (VAS), varied from 4.4 ± 0.4 (for grated carrots), to 7.5 ± 0.4." (Allriot. 2014)

After this first visit, the subjects were then invited to four experimental sessions, in a randomized order, each session separated by at least 7 days: two were conducted in IPB for behavioral explorations; the other two took place in Rhône-Alpes Research Centre for Human Nutrition (CRNH) for metabolic explorations.

Please note: What the scientists observed in the study at hand, as well as in their previous research does not confirm that eating more frequently will make you obese. It does however provide significant evidence against the "eat more frequently to stay lean"-hypothesis that's still rattling around in the mainstream media and certain parts of the fitness community.

At first this may seem awkward, but by having four sessions in different locations the scientists tried to minimize environmental confounders. Furthermore, the order of the four testing sessions was randomized across the participants to prevent any order effect (the random allocation sequences were generated by a biostatistician using a 2-step randomization).

• Subjects were requested to avoid vigorous activities and to abstain from alcohol consumption the day before each session. 
• Subjects were also asked to select a dinner they consume regularly and to eat this same meal the evening before each session. 
• Subjects were also instructed tofinish eating this dinner by 9:00 pm and to eat nothing else after this time. 

For the four sessions, the subjects were given each time the same 674.8 kcal breakfast, the sole difference - you probably suspected this already, when you read the quotation in the introduction to this article - was the time they had to consume this meal, i.e.

• 20 min in  T0 (8:00 am) (F1 condition) or 
• 4x10 min long (168.7 kcal each) every hour at T0, T60, T120 and T180 min (F4 condition). 

The breakfast in F1 was composed of white bread (40 g), croissant (80 g), strawberry jam (30 g), unsalted butter (10 g), orange juice (120 g), white sugar (10 g), and black coffee or tea (400 ml). For each of the four eating episodes of F4, these quantities were divided by 4. Subjects were asked to eat all the food provided for breakfast. As mentioned earlier, they received both breakfasts (F1 and F4) on two occasions: once in the IPB, once in the CRN.

Ok, you know the results, but ....

... let's still take the time and check out the quantitative differences between the metabolic response to grazing (F4 condition) vs. regular food consumption (F1) in the 17 obese male study particpants (BMI 31.9kg/m²).

Figure 1: Subjective satiety and hunger scores in the obese subjects during the 2x2 testing conditions (Allriot. 2014)

What is certainly interesting, is that even the subjective advantages in hunger and satiety were very transient and, if you take a look at what the subjects ate, you will probably argue that this is no wonder: I mean, you don't believe you can gobble down white bread, a croissant with strawberry jam and unsalted butter and a cup of sugar-sweetened coffee all at once without a significant elevation in insulin of which you as a SuppVersity reader know that its satiety effects are blunted in obese / insulin resistant individuals, do you?

Figure 2: Insulin (left) and NEFA (right) levels after the test-meals (Allriot. 2014)

While I am not sure how differences such as those you see in Figure 2 were statistically non-significant, I can tell you that the increase in NEFAs in the "regular eaters" (F1) at T ~ 220min goes hand in hand with the previously reported increase in fatty acid oxidation that was - just as the increase in NEFA - blunted, when the subjects "grazed" their breakfast.

Bottom line: You want it really short? Don't fu**** graze / eat 10x a day! Despite the beneficial impact on appetite sensations and on ghrelin and GLP-1 concentrations, this study provides evidence that an isocaloric increase of the number of eating episodes does not have a short term positive effect on energy intake in obese men.

Suggested Read: " "Breakfast Keeps You Lean" Myth or Mystically True? Bias + Unwarranted Causal Implications" | read more

Contrary to what the authors write in their conclusion, this does eventually stand in line with findings in lean individuals, where a similar reduction in dietary thermogenesis and inhibited lipolysis was observed (Allirot. 2013). This is obviously of paramount importance for us, because it confirms that "the beneficial short-term effect of increasing eating frequency on appetite in lean men considering subjective, physiological and behavioral data" are not worth the anti-weight loss effects due to the reduced thermogenecis and decreases in lipolysis "that could be deleterious on energy balance in the long run." (Allriot. 2013) - for once, I have nothing to add, here ;-)

References:

• Allirot, Xavier, et al. "An isocaloric increase of eating episodes in the morning contributes to decrease energy intake at lunch in lean men." Physiology & behavior 110 (2013): 169-178.
•  Allirot, Xavier, et al. "Effects of a breakfast spread out over time on the food intake at lunch and the hormonal responses in obese men." Physiology & behavior (2014).