2009 Studies & Research Blog

At one point or another, almost all of us overeat.  It could be at Christmas, at Thanksgiving, after a long and hard week where you just used food for comfort, or some other factor, but there’s a good chance that after that period of overeating, you felt at least somewhat guilty.  You may have worried that you’d set yourself back – undone all the hard work you just put in the previous week and are now starting the week over again.

Is this really the case though? And, is there anything you can do to offset this overfeeding?

Researchers out of the University of Massachusetts wanted to assess what the influence of an energy surplus was in terms of circulating concentrations of leptin, insulin, and ghrelin.  Leptin is a hormone in the body that senses current body fat stores and energy intake, working to regulate hunger and the metabolic rate in the body. Insulin is the primary hormone that is released when you consume carbohydrates, working to take the glucose into the muscle cells.  Finally, ghrelin is another hormone that works with leptin to stimulate hunger and is produced by the fat cells.  When it is present in the body in high concentrations, you will feel a great deal hungrier and be stimulated to eat.

When you consume more calories than you typically do, this energy surplus will raise the concentrations of leptin and insulin in the body while decreasing the concentrations of ghrelin.  When you exercise, the exact opposite occurs.

Therefore, the researchers wanted to observe whether exercise could counter the hormonal effects of the energy surplus regardless of energy balance.  They first assessed the plasma concentrations of all three hormones at baseline and then after an overfeeding period, and finally, after an overfeeding period that was accompanied by exercise.

The overfeeding process took place over a three day period total, where they were overfed by an amount of 3213 +/- 849 kJ/day after coming off a two day period of maintenance eating. For the exercise group, an equal net energy surplus was generated for 24 hours by doubling the overfeeding amount and countering it with an exercise sessions that burned the number of calories to make both situations equal again.

After the test was taken, when looking compared with baseline, leptin levels went up after the overeating group without exercise but was not significantly higher after the overeating plus exercise group. Additionally, insulin levels were higher in both overfeeding without exercise and overfeeding with exercise.  Lastly, overfeeding without exercise had no impact on the ghrelin concentrations in the blood, however the overfeeding plus exercise group actually lowered them.

From these results we can see that the impact of overfeeding on leptin and insulin levels does depend upon energy balance, however the ghrelin response to overeating can be counteracted by exercise.

While you should never use exercise as a way to ‘compensate’ for chronic overeating as that can lead to a number of problems, both physical and psychological, this study does suggest that you can offset some of the impacts of overeating by partaking in exercise after.

Reference:

Braun, B., Hagobian, TA., & Sharoff, CG. (2008) Effects of short-term exercise and energy surplus on hormones related to regulation of energy balance.  Metabolism. Mar;57(3):393-8.