|Gluttony is one of the 7 sins - no wonder that eating more than you "deserve" makes you ugly and sick.|
Nevertheless, Jean-Phillipe Walhin and his colleagues from the University of Bath demonstrate in their most recent paper that the ability of exercise to blunt the ill health effects of short-term overfeeding is a non-negligible part of the 'health equation'.
Don't worry this is a human trial!
For their experiment Jean-Philippe Walhin, Judith D. Richardson, James A. Betts, and Dylan Thompson recruited healthy, "habitually active" male volunteers aged 25 ± 7 years. Eligible were only men who participating in structured vigorous-intensity exercise for thirty minutes or more, at least three times per week. After 26 athletic young men who met these criteria were found, they were randomized to one out of two groups by a third party and put on ...
- a fixed energy surplus for 7 days on which their physical activity was restricted (SUR), or
- the same energy surplus and general activity limit, but w/ daily cardio training (SUR+EX).
The energy expenditure was compensated!
As a regular here at the SuppVersity you will be aware that this study would hardly have made it into the SuppVersity articles, if that, i.e. one group eats + 50% and sits around all day, while the other consumes the same amount of energy and works out, would be all the experiment had to offer. What makes the paper actually interesting is something the scientists marked as "critically" in the abstract to their paper:
"[T]he SUR+EX group received additional dietary energy intake to account for the energy expended during exercise; thus maintaining a matched energy surplus." (my emphasis in Walhin. 2013)Practically speaking this meant that the subjects in the SUR + EX group had to eat even more food to achieve an additional +25% increase in energy intake that was meant to compensate for the extra energy the subjects in this group would be burning during their daily exercise sessions.
Q: How did the scientists know that +25% was the correct number? A: They calculated it: EPOC (6.6% of the energy expended during the run) + diet induced thermogenesis (10%) - energy that would have been expended when the subjects rested = approx. 25% of the baseline intake.If we take the 'energy bonus' of +25% into account, we are thus dealing with a comparison of a +50% energy intake diet without exercise and a +75% energy intake diet with exercise. Whether or not this would yield a "matched energy surplus" is something I personally don't care about.
Why? Well, outside of a metabolic ward you got to rely on a bunch of funky equations and the hilariously stupid assumption that energy intake and energy expenditure would not depend on each other. Against that background, it does not really matter that the data in Figure 1 indicates that the energy surpluses ended up being ca. 18% apart. In view of the unreliability of these kinds of 'energy in vs. energy out' calculations, this is still close enough to qualify the energy surplus as being roughly identical.
|Figure 1: Total energy intake and calculated energy surplus (in kcal/day) in the SAR vs. SAR+EX groups (Walhin. 2013)|
|Figure 2: Relative changes (% of baseline) in glucose + fat metabolism, adiponectin, leptin and alanine transaminase levels (the latter a considered a measure of liver strain) during one week of overfeeding (Walhin. 2013)|
Not shown in Figure 2 are the results of the gene essays the scientists conducted. Unsurprisingly, the results are not significantly different. It's once more the "lazy" SUR group, in whom the gene expression in the fat (=adipose) tissue turned from 'neutral' to 'pro-diabetic and -dyslipidaemic:
"Seven of 17 genes within adipose tissue were differentially-expressed in the SUR group; expression of SREBP1c, FAS and GLUT4 was significantly up-regulated and expression of PDK4, IRS2, HSL and VISFATIN was significantly down-regulated (P≤0.05)." (Walhin. 2013)It is thus no wonder that AMPK, one of the most important markers we have, when we are talking about issues with blood glucose management (learn more), or, even more specifically, the ratio of phosphorylated to unphosphorylated protein was also significantly down-regulated elusively in the SUR group (P=0.005).
- Walhin JP, Richardson JD, Betts JA, Thompson D. Exercise counteracts the effects of short-term overfeeding and reduced physical activity independent of energy imbalance in healthy young men. J Physiol. 2013 Oct 28.