While it may sound backwards, there could be some benefits to having a little extra fat on your body — at least, if you’re in your 50s, that is. According to a new study, middle-aged people with a body mass index (BMI) in the category of slightly overweight had higher chances of living longer than any other weight category.

BMI is a calculation of weight and height meant to measure for obesity. It’s used throughout health care facilities in the U.S. as a way of predicting any obesity-related health risks, however, some believe it should be replaced with measures that factor weight in relation to muscle content. That’s because having some weight has been shown to be beneficial to a person’s health. Specifically, among those who are sick, a little extra fat may hold the necessary energy that person needs to overcome their illness. The researchers also found that those who were underweight with the same condition were four times more likely to die.

These reasons could also explain why slightly overweight people (BMI of 25-29.9), aged 51 to 61, had the highest rate of survival over the course of 16 years, researchers said. This group was followed closely by those who moved from slightly overweight to obese (BMI of 30 to 34.9), which was then followed by those who were of a normal weight (BMI 18.5 to 24.9), those who were obese, those of normal weight who lost more weight, and finally, those who were overly obese (BMI of 35 and up). In fact, only 7.2 percent of deaths were due to weight gain among obese people.

“This suggests that among overweight people at age 51, small weight gains do not significantly lower the probability of survival,” Hui Zheng, lead author of the study and assistant professor of sociology at The Ohio State University, said in a statement.

The researchers looked at data from the Health and Retirement Study, which surveyed Americans born between 1931 and 1941. The study included 9,538 participants who were surveyed in 1992, and then interviewed them again every two years afterward, until 2008. Zheng and his team looked at information regarding BMI changes among the participants, and at whether or not they died before Dec. 2009.

The results held even after accounting for smoking and chronic illnesses, Zheng said. “A small amount of extra weight may provide protection against nutritional and energy deficiencies, metabolic stresses, the development of wasting and frailty, and loss of muscle and bone density caused by chronic diseases.”

But although it may help older people, it’s not safe for younger people to pack on the pounds, he warned. One reason: they just don’t get sick as often. Still, he emphasized that the main finding from this study was that any weight gain isn’t good.

According to the CDC, over a third of American adults are overweight, putting them at the most risk for obesity-related diseases, such as heart disease, stroke, type 2 diabetes, and some kinds of cancer.