The notion that exercise helps you lose body fat is controversial. No one argues whether exercise burns or oxidizes calories, instead, the controversy is how exercise may affect other factors associated with fat loss, such as appetite. One author, Gary Taubes, has written articles and books espousing the need to control insulin as the most effective way to lose body fat. For this purpose, he suggests that a low carbohydrate diet is the best way to go for fat loss. Indeed, studies that compare typical low carb diets to high carb, low-fat diets, almost always show a superior fat loss for the low carb regimes. But other studies show that while the initial weight loss with a low carb diet occurs more rapidly compared to other diets that don't restrict carbs as much, after a few months the weight loss with a low carb diet slows considerably to the point where, at the end of a year, the amount of weight-loss that occurs with a low carb diet is comparable to either low fat or classic calorie-restricted diets. There are reasons to explain this, however. In most studies that have examined the effects of low carb diets, the diet starts out as low carb diets (defined as 100 grams of carbs a day or less) but carbs are gradually added back into the diet, so after a few months, it is no longer a true low carb diet. In some studies, the subjects don't exercise, and weight-training exercise is known to help maintain lean mass when dieting. If you lose an excessive amount of lean mass, mainly muscle, while dieting, your resting metabolism drops significantly, setting into motion a body defense system known as Adaptive thermogenesis, which is just a fancy term referring to the need for fewer calories to maintain your weight than previously existed prior to the diet. It is most often caused by too low a caloric intake coupled with a loss of muscle mass.
Authors such as Gary Taubes say that exercise doesn't help a dieter's efforts to lose excess body fat because while you burn more calories when you exercise, your body compensates for the loss of energy by increasing mechanisms that result in a greater sense of hunger. So, according to Taubes, you wind up eating all the calories and more that you burned during the exercise session. However, many other studies dispute this notion of increased appetite following exercise. These other studies find an opposite conclusion: exercise, if anything, blunts appetite leading to less food intake. When I first read Taube's notion that exercise can make you ravenously hungry, I found it curious. In my case, I have no appetite for any type of food for about 2 hours . . .