I'm writing on this topic because of an article I read, yesterday, and because it continues to be a topic of confusion. This isn't a simple matter, so it is understandable why!
I don't want to reference the article. It was written for industry professionals, so it is technical, anyway, and I worry that reading the article would send the wrong message to those that don't understand the jargon and intent. This isn't meant to be an insulting statement. I would have no luck understanding research on complicated medical issues or rocket science, either.
The takeaway of the article is that the research conducted concluded that it was a person's diet that effected weight loss, and not their activity level. Participants that were more active showed no significant difference in weight management/change than those that were sedentary. Only when diet was assessed, was there a correlation. The results of the experiment seemed to show that exercise did not matter or did not affect weight loss efforts among the participants. Of course, this was NOT to say exercise didn't matter! Again, this was looking at a very specific response in a very specific area.
The danger in reading this article by laymen is this: The experiment was very specific and only addressed the fact that active people did not fair any better than sedentary people when they all ate fast-food on a regular basis when it comes to weight management. It is important to state that general health and fitness level were NOT being assessed by this experiment and, therefore, were not analyzed.
Controlling your diet is how you are going to manage your body composition, whether you want to lose mass or gain it. That is undisputed.
But, exercise is the tool that is going to shape your body. Exercise (or lack thereof) is going to control whether your weight gain/loss is a change in lean mass or body fat. The more lean we are, the more calories we will burn at rest. And, if we don't perform enough activity to warrant the need for all that lean mass, then our bodies will drop it, because it is expensive to maintain (it requires more calories and more activity).
Simply put: Eating controls our weight, but exercise controls whether that weight is lean or fat.
The complexity comes in how much food, and what type, it takes to affect your body in the specific way you want it to, combined with how much activity and what type.
