TheMumbler said:
It is years since I did physiology but I thought part of the thing with weight loss and excercise is that increasing your metabolic rate for over 20 mins (roughly speaking) increases your Basal Metabollic Rate (BMR) for a fair period of time afterwards (couple of hours maybe, I forget) afterwards so your calorie usage will be higher than the amount that you need to simply carry out the activity. Figures like the ones you are quoting don't generally take into account the energy costs of increased BMR and repair to the body, building new muscle etc etc.
from
http://www.activelifestyle.info/index.p ... l_the_Burn
Does Exercise Change BMR?
The answer to this question requires looking at two other issues:
Does metabolism stay elevated after a single exercise bout? The good news is that after finishing a hard exercise session, your metabolic rate does remain elevated, even though youâre no longer exercising. The bad news? The increase is short-lived, and usually uses only a few calories. To estimate how long your metabolism is increased, you can monitor how long it takes your heart rate to return to normal after exerciseâand the fitter you are, the shorter the time.
Does exercise increase BMR, so that even if you havenât exercised for a day or two, youâll still be burning calories at a higher rate than if you were inactive? Numerous studies tried to answer this question. Hereâs what their results show:
Aerobic exercise does not increase BMR. However, it does increase your RMR, or your metabolic rate during a period of rest immediately following exercise, but this is short lived. (Aerobic exercise is an excellent way to burn calories and build cardiovascular fitness.)
Although the results are mixed, strength exercise may increase BMR slightly (about 5%), especially if muscle mass increases and fat decreases. The ârestingâ metabolic rate of muscle is not large, but it is higher than fat.
Strength training may reduce the decrease in BMR that occurs with low-calorie dieting.
The Take Home Message?
The possibility of small, but real, increases in BMR are yet another reason to add strength training to your routine. Donât expect magicâyou wonât get it. But remember that most adults gain weight very slowly throughout life, reflecting small excesses of food intake over energy expenditure. So small increases in BMR just might offset that gradual weight gain.
I can find plenty of other references that basically say the same, so even the most pro exercise sites, when they publish figures basically admit that exercise plays an insignificant part in weight loss unless you are a dedicated ultra endurance type. Of course exercise is good for you, not disputing that, and can help maintain weight, but it is highly overrated as a means of weight loss and can cause hunger and thirst pangs plus the 'reward' trigger which can have the opposite effect. ie. the quick pint after a gym session.