September 10, 2009 – It is common to gain several pounds after dieting. But engaging in regular physical activity would limit this weight gain, among other things thanks to its “appetite suppressant” effect.
As a general rule, after following a long-term diet, we regain more than 35% of the weight lost in the following year.
Why? The body tries to compensate for the lack of food by increasing the appetite, while seeking to reduce physical activity to limit energy expenditure. Clearly, our body recharges the batteries, and sometimes even beyond what we had lost! This is the famous “yo-yo effect”.
But researchers in Denver, Colorado, have discovered how physical activity can change this pattern.1.
For 16 weeks, they fattened rodents genetically predisposed to get fat, then put them on a rigorous diet that caused them to lose 14% of their weight. After maintaining their new weight for 16 weeks, they could eat without restriction again. Half of them had to exercise while the rest remained sedentary.
Appetite suppressant effect
Result: 60 days after resuming ad libitum feeding, sedentary rodents regained up to 120% of the weight they had lost, compared to 77% in active rats.
The researchers noticed that during digestion, sedentary rats first burn carbohydrates which serve as rapid fuel for the muscles. However, the early use of carbohydrates awakens the appetite and encourages eating more.
Active rodents burn fat first. The resulting saving in carbohydrates therefore reduced the appetite of active rats.
In addition, the researchers found that among sedentary rats, a return to an unrestricted diet resulted in the formation of new adipose (fat) cells in the abdomen. Conversely, regular physical activity reduced the appearance of new fat cells in active rodents.
This discovery challenges the hypothesis that the number of fat cells is determined in advance by an individual’s genetic makeup. “Exercise prevents the formation of new fat cells, rather than simply reducing the size of pre-existing fat cells,” write the study authors.
Help to move!
Overall, they believe that regular physical activity, following a diet, promotes a new physiological balance through which the body manages its energy better and avoids storing too much fat.
However, researchers agree that adopting an active lifestyle is not always easy, both in humans and in rats.
As proof, even the rats considered active showed a marked decrease in their will to move, once they were able to binge again.
Laboratory technicians even had to be more proactive in getting rodents to untie their legs on the “treadmill”. However, the study does not say how they did it …
Martin LaSalle – PasseportSanté.net
1. MacLean PS, Higgins JA, Wyatt HR, et al, Regular exercises attenuates the metabolic drive to regain weight after long-term weight loss, Am J Physiol Regul Integr Comp Physiol, September 2009, vol. 297, no 3, R793-802.