Spiro, exercise is pretty useless as a way to lose weight. It has health benefits, but weight loss isn't really one of the good ones.
"There was a time when virtually no one believed exercise would help a person lose weight. Until the sixties, clinicians who treated obese and overweight patients dismissed the notion as nave. When Russell Wilder, an obesity and diabetes specialist at the Mayo Clinic, lectured on obesity in 1932, he said his fat patients tended to lose more weight with bed rest, while unusually strenuous physical exercise slows the rate of loss.
The problem, as he and his contemporaries saw it, is that light exercise burns an insignificant number of calories, amounts that are undone by comparatively effortless changes in diet. In 1942, Louis Newburgh of the University of Michigan calculated that a 250-pound man expends only three calories climbing a flight of stairsthe equivalent of depriving himself of a quarter-teaspoon of sugar or a hundredth of an ounce of butter. He will have to climb twenty flights of stairs to rid himself of the energy contained in one slice of bread! Newburgh observed. So why not skip the stairs, skip the bread, and call it a day?
More-strenuous exercise, these physicians further argued, doesnt help mattersbecause it works up an appetite. Vigorous muscle exercise usually results in immediate demand for a large meal, noted Hugo Rony of Northwestern University in his 1940 textbook, Obesity and Leanness. Consistently high or low energy expenditures result in consistently high or low levels of appetite. Thus men doing heavy physical work spontaneously eat more than men engaged in sedentary occupations. Statistics show that the average daily caloric intake of lumberjacks is more than 5,000 calories, while that of tailors is only about 2,500 calories. Persons who change their occupation from light to heavy work or vice versa soon develop corresponding changes in their appetite. If a tailor becomes a lumberjack and, by doing so, takes to eating like one, why assume that the same wont happen, albeit on a lesser scale, to an overweight tailor who decides to work out like a lumberjack for an hour a day? "
http://nymag.com/news/sports/38001/