Here is a good review article(pdf) on how diets and exercise interact to affect weight loss and other variables.
Here is how I would summarize the main points:
1. Any diet program without an exercise component results in lowered fat-free mass and a lowered resting metabolic rate.
This is consistent over a number of studies.
2. Without any calorie restriction, aerobic exercise leads to a small decrease in fat mass and resistance exercise leads to a small increase in lean mass.
Nothing too shocking there.
3. Diets combined with aerobic exercise generally lead to a reduction in lean mass and a reduction in resting metabolic rate.
Said differently, aerobic exercise is not enough to offset the reductions in lean mass and RMR from calorie restriction.
4. Diets combined with resistance exercise generally lead to no change in lean mass or resting metabolic rate.
I’ll have more to say about this in an upcoming post.
These conclusions aren’t ground-breaking or anything, but I wanted to lay them out for future posts.