A slice of bread pasted with jam and butter containes some 150 kcal. To be able to burn up this much body needs workload equivalent to strenuous exercise for half an hour or a 3 mile run.
How many of us can do it !!! By far the only way of shedding excessive weight is to eat fewer calories, fewer that those expended. Lossing weight should be a gradual process. There is no miraculous diet which would take off extra large amount of weight with in a few days without toiling hard. Complete fasting for a week is difficult and inadvisible, but even if it is accomplished it would take away not more than 5 pounds of body fat.
The best way to fight obesity is to consume a properly balanced low caloric diet, to be accompanied by bouts of exercise.

Overweight people who manage to lose just a little bit of weight - even just a pound a year - may substantially lower their risk of high blood pressure. The hard part, of course, is keeping the weight off. But a new study shows that surprisingly little weight loss - if it can be sustained - carries a big payoff in better health.

If you're overweight, losing just a pound or two a year--and keeping the weight off--can help prevent diabetes, researchers report. The more weight lost, the bigger the reduction in diabetes risk, the investigators note. In a long-term study, the risk of developing diabetes was 33% lower in overweight people who lost between 8 and 15 pounds, while those who lost more had a 51% reduction in risk.

Women who repeatedly gain and lose weight, especially if they are obese, have significantly lower levels of HDL or "good" cholesterol than do women who maintain their weight. While severely overweight women should try to reduce their weight to avoid the many health problems caused by obesity, women who are not obese should try to maintain a stable weight. 

Being overweight and having high blood pressure can independently increase a man’s chances of developing kidney cancer, according to a new study.