to add to what you're saying It seems counterproductive to overemphasize exercise over diet or vice-versa. I think adding perspective also helps. -Doing a quick google search it's alleged that 1-lb of fat requires a caloric deficit of ~3500 calories. Walking 1-mile burns 100± calories which means it would require roughly 35-miles of walking to burn 1-lb of fat. -That's a challenging proposition to acheive without adding extra food just for increased energy and as you added, that doesn't necessarily account for increased muscle mass. It's also pretty easy to develop a nutritional deficiency through diet alone and speaking anecdotally, I've never achieved much weight loss without a combination of both diet and exercise.