Exercise may cause physiological changes that help us conserve energy
Many theories explain why exercise isn’t great for weight loss. Exercise changes our bodies to regulate energy, which researchers call metabolic compensation. Loyola University exercise physiologist Lara Dugas says when we stress our bodies through exercise, the body’s compensatory mechanisms are activated and can actively fight our efforts to lose weight.
A 1994 study that was published in the journal Obesity Research showed that strenuous exercise and monitored food intake had minimal effect on weight loss and the number of calories burned. Seven pairs of sedentary twins went through 93 days of intense daily two-hour exercise sessions. They also had their food intake monitored under 24-hour supervision by nutritionists. Every calorie was measured to make sure the energy intake was the same for all the pairs of twins.
At the end of this research period, the average weight loss of the participants was only 11 pounds, and it was mostly the result of fat loss. The researchers discovered that the participants burned 22 percent fewer calories through exercise than they had anticipated. The researchers concluded that the basal metabolic rate of the participants was slower than normal outside of the two-hour daily exercise block.
A recent 2016 study led by Kevin Hall looked at 14 contestants from the Biggest Loser reality show. The contestants had their body weight, fat, metabolism, and hormones measured at the end of the competition in 2009 and again in 2015. The contestants lost a lot of weight, but in 2015, their waistlines had largely rebounded. The biggest surprise was that their metabolism had slowed down and they were burning 500 fewer calories per day. This resulted in the contestants slowly regaining the weight they lost.
Lara Dugas calls this the survival mechanism where the body is trying to hold on to the stored fat for future energy needs. Researchers do not know why this happens or how long it lasts. They also do not know how much fat the body tries to retain or how this survival mechanism affects different groups of people.
