After six months, the non-diet group had lost an average of 1% of their weight, the calorie restriction group, 10.4%, those who were on a calorie restricted diet plus exercise, 10% and the very low-calorie diet, 13.9%.

BBC: NEWS | Health | Low-cal diet 'long-life benefits'

"I would never recommend doing a very low-calorie diet alone, " says Hernried.

CNN: Extreme diets: Life on 800 calories a day

The drug, which is based on a chemical found in red wine that is thought to mimic the life-prolonging effects of a very low-calorie diet, proved safe.

ECONOMIST: Business this week