I’ve seen where several news outlets have written about a new diet study published this month. The study, published in JAMA, compared the Atkins, Zone, Ornish, and LEARN diets in overweight women.
The Atkins diet showed the most weight loss – 10 pounds after 12 months. To some this "proves" the superiority of the Atkins diet. However, I accessed the full-text of the study and came to very different conclusions.
First, the study measured weight loss, but did not differ between fat loss and muscle loss. Typically in diet-only studies, participants lose a substantial amount of lean mass.
Second, all the groups (except for the Ornish group, which lost the least body fat anyways) regained body fat from month 6 to month 12. This is again typical of diet studies. The majority of weight is lost in the first six months, and then the weight is slowly regained over the course of a year or two.
Why do researchers keep wasting money on diet studies? I am aware of no study that shows a weight loss of more than a pound or two if the study is carried out into multiple years. Exercise is the only long-term way to reshape the body.