The Diet Trap Revisited: Yo-Yo Effect, Decreased Basal Metabolic Rate and the Myth of Fat-Free Mass Losses. Plus: Gender Discrimination and the "Diabetic Advantage"

Image 1: Geoffrey Cannon's "Dieting Makes You Fat" was first published in 1983 and has lost nothing of its topicality.

According to relatively recent data (Bendixen. 2002; Kruger. 2004), roughly 30–50% of the women and 10–30% of the men are currently or have recently attempted to lose weight by "dieting". I would assume that at least 90% of these dieters followed did so by just following the "Hippocratic approach" to weight loss of eating less and exercising more a strategy that is probably even more futile today, than 400BC, when it was first proposed by the father of modern allopathic medicine (cf. Precope. 1952), or 1983, when Cannon and Einzig published the first of the countless editions of their explanation for why dieting is a disaster (which is  by the way, not just because a calorie was not a calorie ;-).

Dieting makes you fat - fullstop!

From earlier as well as more recent studies on the effects of starvation, calorie restriction and exertional physical training, sleep and energy deprivation during boot camp like activities in the army, we know that prolonged caloric restriction and/or exercise induced energy deficiency will lead to hyperphagia and a subsequent "fat overshoot". As the data in figure 1 goes to show, the latter can be pretty profound and ranges from +2.7kg in the seminal fasting study by Benedict from 1907 up to 6.5kg in the well-powered (n=700) food rationing study, Fleisch et al. conducted after WW2.

Figure 1: Fat gain (in kg) after fasting, restricted eating and boot-camp like training in an energy deficit (left) and lean mass and fat loss and regain in the Minnesota experiment (data based on summary by Dullo. 1997 and  Keys. 1950)

A very similar scenario was also simulated in the so-called Minnesota experiment by Keys et al. (Keys. 1950) in the course of which thirty-two healthy volunteers were kept on semi-starvation diets for 12 weeks. During the subsequent 12 weeks their caloric intake was gradually increased until, for the last 8 weeks of the study, they had free access to food. From A brief glimpse at the data in figure 1 (right) should suffice to be able to tell that this type of "controlled re-feed" despite being conducted over a 12-week period did not prevent the +80% body fat overshoot in the subsequent ad-libitum feeding phase - and that despite the fact that the total caloric intake of the subjects had returned to baseline in week 7 of the ad-libitum phase (after temporary overshoot of up to +60% in week two, though).

Did you try to lose weight in puberty? Well that's the reason you are fat, now.

A 1999 study by Stice et al. shows that it does not even take a 12-week period of restriced eating (-50% in the Minnesota experiment) to get caught in the vicious circle of yo-yo dieting. For the 692 female teenagers from the ninth grade of a a Californian high school, even the allegedly harmless "I got to get in shape for spring" diets, were associated with a statistically significant shift in  the onset of obesity (Stice. 1999). With anxiously monitoring your caloric intake and being only marginally less detrimental than actual dieting:

• caloric restraint: +192% increased chance of early obesity (p < 0.001),
• dieting (self-labeled): +224% increased chance of early obesity (p < 0.01),
• exercise or weight control: +25% increased chance of early obesity (p < 0.01)
• (ab)use of laxatives / appetite suppressants: +85% risk of early obesity (p < 0.1)

In this regard it appears to be somewhat unfair that women are not only more susceptible to the diet trap due to the bad role models and ill advice they are presented with on a daily basis (cf. "Strong is the Better Sexy! Female Athletes as Role Models"), but - as the recent re-evaluation of existing data on the effects of dairy and/or calcium rich diets and resistance training on weight loss in 72 obese(BMI 33.4kg/m², 38.8% body fat) middle-aged (56y) caucasian men and women would suggests (Soares. 2012) - also suffer from a significantly more pronounced reduction in basal metabolic, and more importantly fatty acid oxidation rate after weight loss (-5.2kg fat; -2.3kg lean mass).

Figure 2: Basal metabolic rate (BMR) fatty acid and carbohydrate oxidation rate (FOR, COR) before and after weight loss interventions in subjects with and without metabolic syndrome (left); changes in BMR, FOR and COR in male and female study participants (data adapted / calculated based on Soares. 2012)

Irrespective of the sex of the subjects, participants who recovered from metabolic syndrome as a result of their weight loss suffered the greatest reduction in metabolic rate

• 484kj/day and 414kj/day reduction in the subjects who were either healthy or whose metabolic syndrome did not go into remission vs. 
• 670kj/day reduction in the "lucky" ones who got rid of their metabolic syndrome (criteria according to Alberti. 2009)

While Soares et al. can only speculate that these gender differences may be related to differences in either glucose or adiponectin metabolism, the initially counter-intuitive finding that the remission of the metabolic syndrome appears to predispose to future weight gain ue to reductions in basal energy expenditure bring the results of another relatively recent study to mind, in which Miyake et al. were able to show that within a cohort of  thirty obese Japanese adults with pre-diabetes (n=7), type 2 diabetes (n=13) or without diabetes (n=10) the diabetic subjects had 7.1% higher basal metabolic rates than the non-diabetic study participants (after adjustment for fat-free mass, fat mass, age, and sex; Myiake. 2011), with a statistically significant correlation between residual BMR and fasting glucose (r=0.391, p=0.032).

The diet trap and the myth of reductions in fat-free mass

Figure 3: Ratio of resting metabolic rate to fat free mass before and 4 and 8 weeks after a protein sparing fast; means, top; individual, bottom (Elliot. 1989)

Overall, these results only confirm the longstanding findings of e.g. Elliot et al. and Weinsier et al. who were able to show that the often touted linear relationship between resting or basal metabolic rate and fat-free mass does not exist - neither in the 1111 non-dieting normal subjects (118 infants and pre-schoolers, 323 adolescents, and 670 adults; Weinsier. 1997) in the Weinsier study, nor in the seven obese women in the Elliot study, who lost an average of 23kg body fat and 5kg of lean mass in the course of an 8-week modified protein sparing fast (Elliot. 1989; cf. figure 3).

So, no matter how you look at it, classic dieting may make slimmer in the short run, but whenever larger caloric deficits and faster weight loss come into play (irrespective of the amount of lean muscle you may lose), caloric restriction and exercising just to lose weight, are going to set you up for a fat rebound!

Challenging the Special K Challenge: Especially Convenient or Especially Stupid 14-Day Weight Loss "Solution"?

Image 1: Is this really all it takes to lose those unhealthy and unaesthetic pounds? Two servings of a breakfast cereal a day, instead of two of your regular meals? Sounds too "good" (?) to be true, right? A study says it works, but only the SuppVersity will tell you the real costs!

For me, as a German, it is quite surprising that the words "Special K", or rather the reference to the eponymous product comes up pretty often in the health and nutrition blogosphere, when someone wants to point out an e-special-ly (K) unhealthy breakfast. While "low fat", still looms large here in Germany and "diet"-this and "diet"-that stickers (respective products usually carry the label "light", which shall obviously imply "light" as in "lightweight") are attached to an ever-growing number of products in the mainstream supermarkets, my fellow countrymen (I am unfortunately not so sure about the women, though) must yet have had advanced access to the data (not just the abstract - but more about that later) of Patricia K. Shaw's master thesis (Shaw. 2011), which has been peer-reviewed and published only recently, and are thusly mostly avoiding this "healthy whole grain" product from a company with a >13b revenue in 2010.

"Special K Challenge" - What does it challenge? Weight loss or yo-yo-effect?

In the respective 14-day intervention trial 24 subjects (12 men and 12 women) with a mean age of 34.7 years and a pretty chubby physique (BMI 28.6 kg/m², but body fat 28.8% and 40.7% for men and women, respectively) had to follow the "Special K Challenge" (official website), the central idea of which is that you are going to lose weight and get healthier if you replace two of your regular meals by a predefined amount of yummy (and nutritious *rofl*) expensive cornflakes, ah... I mean "Special K"...

Figure 1: Macronutrient composition of the 174kcal Special  K + skim milk "meal replacement" and the Special K Snack Bars (83kcal) and Mini Breaks (99kcal) the participants consumed during the 14-day challenge and the consequent reductions in protein and fat intake relative to baseline (data calculated based on Shaw. 2011)

In view of the fact that everyone appears to be on the lookout for an easy and above all convenient way to lose weight, it was not difficult for Mrs. Shaw to recruit their subjects among the faculty staff and senior students from the University of Limerick, who actually had to do nothing, but adhere to these two "protocols" for 2x14 days:

1. Control phase: Do what you usually do and eat what you usually eat for two weeks, log all your foods and get back to the lab to get another body weight, body water, body fat, lean body mass (the latter two via DXA scans), waist and hip circumference measurement taken.
    
2. Special K Challenge: Keep doing what you usually do, keep eating what you usually eat, but replace 2 of your main dishes with Special K + semi skimmed milk and eat fruit and/or Special K Mini Breaks or Special K Snack Bars between meals (cf. figure 1), log everything you eat and return your hopefully lighter self as well as the logs to the lab in another two weeks.

About as convenient as the average pizza-ordering slacker likes it, right? It is thusly not really surprising that the overall compliance of 83% was above what you usually see in dietary interventions.

"I want my pizza back!"- and "I better completely stop eating to maximize weight loss"-effect

What is similarly unsurprising, is that the overall calorie intake is reduced (avg. energy deficit: 673kcal/day) by a "challenge" , in the course of which two of the main meals (of which most people obviously consume only three) are replaced with a 174kcal "meal replacement" in form of yummy cornflakes with watery skim milk (aside from the "bah, I want my pizza"-effect, I am thinking about the "hyperpalatability hypothesis" here, as well; cf. Guyenet. 2011). That it is so profoundly reduced that at least one male subject had a caloric deficit of 1555kcal per day (!), however, clearly suggests that the end-result of this type of "diet" (or shall we call it a hunger-strike?) is not going to work. It is thus all the more surprising, that, according to the conclusion of the abstract, ...

The results of the present study demonstrate that the Special K Challenge was effective in reducing total energy intake and resulted in a positive, health-related change in body composition. The reduction in total body mass, regional fat mass and waist circumference may act as an effective motivator to long term body mass reduction.

Certainly worth taking a closer look at the data, right? Well, for the first point, i.e. "effective in reducing total energy intake", we already know that this is true. "Effective", by the way, is effectively understated. Now, what about the "positive, health-related change in body composition"? What would that imply? A reduction in body fat and an increase in lean mass, right! And what have we got?

Figure 2: Lean mass and fat mass of 24 overweight  men and women before 2-week accommodation phase (pre) and before (basal) and after (Special K) 14-day "Special K Challenge" (data adapted from Shaw. 2011)

We got a reduction in body fat and a reduction in lean mass - and worst of all, the female study participants, who, with their 40%+ body fat levels already had no muscle to begin with, lost almost twice as much lean mass as body mass. Assuming that they are "scale watchers" (and should read the "How to track your progress on a diet & exercise regimen"), this may in fact have been an "effective motivator", but it is also a profound obstacle to the "long term body mass reduction", unless we want to define that as "starving your muscles away".

"But it does work! So what do you want?"

Even if you are not effected by it yourself, I bet that everyone of you knows someone who has maybe not even gained weight, but has become fatter and fatter with every diet he (or presumably "she") has "done". This study on the "Special K Challenge" shows you exactly what went wrong for him/her/them:

Image 2: Although common wisdom would say so, eating salad is no alternative either... when I come to think about it, it may be an alternative to eating toilette paper, but that won't help with fat (not just weight!) loss either.

• believing in the existence of a "quick fix" and/or "convenient solution" that will work in 1-2 months, let alone weeks and thusly
• going on a diet instead of changing your diet as part of changing your lifestyle 
• not meeting your minimal energy requirements / starving yourself
• not having enough protein and fat with EVERY meal
• snacking, in general, and on processed foods, in particular
• no exercise (in this case), or tons of endurance exercise to exercise your "cheats" away
• using the scale as a measure of success

Taken together, all that programs failure, no matter how "motivating" it may be... or do you really believe the guy with the -1,500kcal/day deficit or his female counterpart with -1,139kcal/day will "stick" to this "diet" for longer than two weeks? I don't! And we both know what happens, when they are sitting with their friends and family at the coffee, next Sunday, right? ... I guess, it is thus unnecessary that I answer the question I raised in the headline, explicitly - Especially Convenient or Especially Stupid? You decide!