Can losing weight be unhealthy?

Overweight people who are otherwise healthy might increase their risk of dying by intentionally losing weight.

A study of 2,957 twins in Finland found that those who were overweight and who lost weight on purpose were about 86% more likely to die for any reason over the next 18 years compared with those whose weight remained stable. The researchers cautioned, however, that only 268 people in the study died, a number too small to justify any firm recommendations about whether overweight people should try to lose weight.

Critics who think health authorities have exaggerated the risks of being overweight said the findings offered fresh support. Other researchers, however, said the study’s weaknesses undercut the findings, and there was overwhelming evidence that being overweight increases the risk of health problems.

The researchers who conducted the study said they hoped the results will stimulate more research.

Many previous studies have found that people who lost weight appeared to have an increased risk of dying over the long term, but the prevailing wisdom has been that weight loss in these studies was the result of illness. Still, some evidence has suggested that intentional weight loss might be unhealthy for otherwise healthy people, perhaps, for example, because losing muscle could have detrimental effects on vital organs.

The study was published in the June issue of PLoS Medicine, a Public Library of Science journal.