If losing weight is difficult, staying slim after a diet can be harder still.
The solution could be as simple as two cups of coffee a day, researchers say.
They have discovered that a regular daily intake of two to four cups helps dieters keep flab at bay once they have shed the unwanted fat.
The high caffeine content seems to help the body resist the gradual weight gain that defeats so many slimmers.
Other caffeinated drinks have the same effect, according to the research team at Hannover Medical School in Germany.