Didn't know whether to post this in Diet or Exercise but here it goes:
Tell me if this makes sense:
Let's say you have a guy who's eating about 1600 cals a day to diet (he's a little guy: 6'2", ~160lb, ~10% bf)on a 40/40/20 split. It seems to me that if you plan on dieting and you want to maintain your LBM and your metabolism you should eat exactly how many calories your body must have to stay the same without any extraneous physical activity (your basal requirement). This way your body doesn't sense a lack of incoming energy and slow down metabolism. Now you take this same guy with his same diet and you get him running ~200m sprints about 10 or more times a day, 3 days a week. This way his body sees that every bit of energy it has coming in will be getting used and then some. Since his activity is akin to weight lifting (high intensity, anaerobic) his body knows that it will need to preserve muscle mass for this regular activity (see Loki's articles on sprinting in Mind and Muscle Mag. for the physical and hormonal changes that will take place), so what's to keep his body from tapping into visceral and subcutaneous body fat stores to make up for this negative energy balance?
My dieting problem is basically this: it seems more advantageous to keep your calories the same as your BMR so that your body doesn't slow down your metabolism, and to simply cause a caloric debt by incrementally inducing more intense physical activity more often. What is the advantage to simply reducing calories over increasing activity because there is a difference between caloric debt from decreased food and caloric debt from increased activity? Why reduce calories and increase activity? Wouldn't that be too taxing?
Hope all that makes enough sense to be able to answer.