“You can never be too rich or too thin,” declared Wallis Simpson, the woman for whose love Edward VIII abdicated the British throne. 

Slenderness could help win royal hearts, but it may not extend your life. A literature review published in the January 2 Journal of the American Medical Association looked at nearly 100 studies involving 3 million adults and found that people considered overweight or even mildly obese had lower mortality rates than so-called normal-weight folks. 

The researchers, led by Katherine M. Flegal of the National Center for Health Statistics, categorized subjects based on body mass index (BMI), which is your weight in kilograms divided by the square of your height in meters. The government-recommended range is between 18.5 and 25, “overweight” is 25 to 30, and obese is 30 or more. Someone who is five feet, nine inches tall, for example, is considered overweight at 169 pounds and obese at 203.

It turns out that people in the “overweight” range were 6 percent less likely to die during the study period than people in the “normal” range, while the mortality rate for mildly obese people (with BMIs between 30 and 35) was 5 percent lower. The risk of death for people with BMIs of 35 or more, by contrast, was 29 percent higher than for normal-weight people.

Why don’t mortality risks correspond to weight guidelines? Flegal et al. say possible explanations include “earlier presentation of heavier patients, greater likelihood of receiving optimal medical treatment, cardioprotective metabolic effects of increased body fat, and benefits of higher metabolic reserves.”