Lately, there has been a lot of conflicting information about exercise and weight loss and control. For a few years, word was that walking for a half hour a day was good enough for you. Now, we're reading that it's not enough to actually lose weight, but it is good for your heart. Additionally, I've been reading lately that exercise simply is not useful at all when you want to lose weight because people who exercise just end up eating more.
The results of these studies are not only disheartening, but misleading. One of the problems with all surveys, studies, and tests is that they take a complex problem and oversimplify it so that they can get scientifically valid results. That is, they look at a limited number of factors and tend to watch behavior only over the short term (less than 2 years, in many cases). What is more, most researchers have a hypothesis before constructing their study and either consciously or unconsciously create conditions that will validate their theories.
If you scrutinize the information that is coming out carefully, you'll see that the interpretation is always spelled out in a particular way. One of the studies noted that certain types of exercise increased muscle mass and muscle burned about 40 more calories per day than fat and all it would take to mitigate any of the gains from having more muscle would be to eat one pat of butter more per day. While this is certainly so, the interpretation completely ignores the fact that you are burning more calories for the duration of the exercise (often around 100 calories or more) and that you are almost certainly suppressing your appetite for the time after exercising and possibly boosting your overall metabolism. In other words, exercising daily, even modestly, has the potential to burn around 150 calories a day or more from combined effects of aerobic activity and increased muscle mass. Even if you eat at a maintenance level (around 2000 calories for an average person), daily exercise should help you lose around a pound a month (possibly more).
Why do the study results focus only on increased muscle mass and calories burned at rest? Why do they assume that anyone who is trying to lose weight would simply decide to eat more just because their exercising happened to work up an appetite? My personal exercise habit is to get the exercise in a few hours after a meal and then rest and pretty much recover from the appetite suppression effects in about the right time for lunch or a planned snack. I don't eat more because I exercise even if I want to, and honestly, I don't find myself being greatly hungrier than usual because I exercise. I'm hungry and fighting it all of the time anyway so there's really not much of a difference.
I have to wonder what motivates this sort of reporting. Is it simply that the winds of information have been blowing one way for awhile so there's nothing new to say and they figure they might as well have them blow another way for a bit? Is it that they see the obesity problem getting worse so they assume they must create a reason?
I don't know why such discouraging news is being reported, and I do know that weight loss is actually more complex than "eat less, exercise more", but I do know that eating less and exercising more will eventually work for most people if they can hold the line against their biological and psychological impulses (which is no small task). My guess is that these studies are likely pointing to the fact that it is much harder to do these things than expected and that people who try to exercise to lose weight end up eating more without realizing it or believe their exercise is burning more calories so they can justify a little indulgence.
The answer would seem to be not to say that exercise doesn't help people lose weight, but rather to educate people about the effects such that they are more cautious about how much they are eating. Essentially, people need to know that exercise when you want to reduce your weight doesn't buy you much of anything in terms of being able to eat more.