Thursday, May 5, 2011

Exercise OR Calorie Restriction? Is This a Valid Question? Differential Epigenetics of Exercise and Calorie Restriction Suggest Otherwise.

It is beyond me, why the war between proponents of exercise based and calorie reduction based approaches to weight loss are still raging. As a faithful "student" of the SuppVersity, you know that I have always been recommending a combination of both for improved body composition, well-being and general health and was pretty angry, when Gary Taubes claimed in the course of Dr. Oz's ridiculous dissertation on the dangers of low carb diets, that exercise would only stimulate hunger and would thus fail to produce a beneficial effect on weight loss and related health problems (cf. video 1, below). A group of researchers (Karrie. 2011) from the Department of Nutritional Sciences at the University of Texas have now conducted a research study that may well shed some light onto what exactly (in this case this means on a epigenetic level) happens in the course of calorie restriction and/or exercise induced weight loss...
Video 1: Gary Taubes on Dr. Oz' show talking about the futility of exercise.
(Dr. Oz, official homepage)
Karrie, et al. had analyzed adipose gene expression in 48 female diet-induced obesity (DIO) mice in response to 8 weeks of either and ad-libitum fed CONTROL diet, a 30% calorically reduced regimen (CR), a treadmill exercise regimen (EX, with ad-libitum control diet), or  a continuation of the hypercaloric high fat diet (DIO) which made the mice fat in the first place (before the start of the experiment). What the scientists found is quite interesting and - at first sight - appear to rectify Taubes' skepticism with regards to exercise:
Relative to the DIO controls, both CR and EX reduced adiposity by 35–40% and serum leptin levels by 80%, but only CR increased adiponectin and insulin sensitivity.
Meaning visible improvements in terms of body fat were almost identical (cf. fig. 1), while favorable metabolic changes in the areas of  the hunger / satiety, insulin and leptin regulating peptide, as well as insulin sensitivity on the receptor level, occurred only in consequence to a reduction in caloric intake beyond maintenance.
Figure 1: Body weight and composition changes after 6 weeks on different diet / exercise protocols.
(data adapted from Karrie. 2011)
Only a few days ago I reported similar results, i.e. no effects of exercise alone on insulin sensitivity in the Layne study.  Other than Layne et al., whose primary focus was on m-TOR and AMPK responses in muscle tissue, the study at hand provides additional data on the differences in the epigenetic responses to calorie restriction, on the one, and exercise, on the other hand, which may well explain the (disappointing) observations:
Gene expression microarray analysis of visceral white adipose tissue revealed 209 genes responsive to both CR and EX, relative to the DIO group.  However, CR uniquely altered expression of an additional 496 genes, whereas only 20 were uniquely affected by EXOf the genes distinctly responsive to CR, 17 related to carbohydrate metabolism and glucose transport, including glucose transporter (GLUT) 4.
What this means is that both exercise, as well as calorie reduction, have 209 gene responses in common (probably responsible for the similar effects on weight loss); yet, additional 496 genes are modulated exclusively by calorie restriction and among these are 17, of which we already know that they are related to carbohydrate metabolism and glucose transport. It is thus suggesting itself to speculate that these genes are the ones, responsible for the beneficial effects on insulin sensitivity, which could not be observed in the exercise only group.

So, was Gary Taubes right, afterall? No. While it may be that exercise alone is not capable to upregulate insulin sensitivity its benefits on overall health, weight loss and above all weight maintenance have been so well established that it would be outrageous to question the advice any sensible nutritional counselor will provide his overweight clients with: Eat healthy (high protein, low / moderate carb, enough fat, whole foods, etc.), and moderately reduce your calorie intake, and begin an exercise regimen that is demanding, but not overcharging. Eventually, when this program has become a habit and the habit becomes a lifestyle, you can be certain that you are never going to be "the biggest loser" again.