Coffee and green tea - do they really boost metabolism

You have heard it a hundred times: drink green tea or black coffee and your metabolism will fire up and the fat will melt. It is one of the most popular weight-loss tips in India, especially the morning green-tea-with-empty-stomach habit. There is some truth in it. Caffeine and the catechins in green tea do raise your energy burn a little. But the size of the effect is small — enough to notice in a lab, not enough to rescue a diet that has too many calories. And if you drink it as a sweetened cold coffee or a sugar-heavy green tea frappe, the sugar gives you far more calories than the tea burns. Here is what the studies actually show.