A recent study examining how 11 different diets affect weight gain and obesity during menopause found that two — the Planetary Health Diet and a diet that supports healthy insulin metabolism — are best for weight management.

The research, published in the journal JAMA Network Open, seeks to fill a gap in studies of diet and weight gain involving women around the age of menopause, during which weight gain is common. The researchers, led by Tong Xia, a postdoctoral fellow in epidemiology and nutrition at the Harvard T.H. Chan School of Public Health and the Channing Division of Network Medicine at Harvard Medical School and Brigham and Women’s Hospital, examined the diets of 38,283 women who participated in the Nurses’ Health Study II, a long-running study of the lifestyle habits of registered nurses who were between the ages of 25 and 42 in 1989. As part of the study, the nurses filled out detailed dietary questionnaires every four years. Researchers examined dietary and weight records during the six years before and after menopause.

“Weight gain during menopause is common, but until now we didn’t know which specific diet actually helps most,” Xia said. “Our study is the first to directly compare 11 major dietary patterns, plus ultra-processed food intake, in the same group of women around menopause. What we found is that not all healthy diets are equal — a low-insulinemic diet and the Planetary Health Diet stood out as most effective for managing weight during this transition, giving women and their doctors concrete, evidence-based guidance for a stage of life when few such answers have existed.”

Researchers found that the Planetary Health and low-insulinemic diets were associated with the lowest weight gain and with the lowest risk of obesity. The Planetary Health Diet was developed by the EAT-Lancet Commission in recent years and has been shown to be both healthy and have environmental impacts that are lower than other diets.

“These two dietary patterns are low in red and processed meats, potatoes, french fries, sodium, and high in nuts, fruits, vegetables, whole grains,” Xia said.

Though the diets can be broadly categorized as either healthy or unhealthy, according to nutritional studies in recent years, the researchers said the dietary details matter so even diets with ample evidence for their health-promoting characteristics, such as the Mediterranean diet and Dietary Approaches to Stop Hypertension, also known as the DASH diet, are distinct because they include different proportions of healthful foods.

The study, supported by the National Institutes of Health and the Julie Wilcox Women’s Health and Nutrition Novel Research Fund, included the Planetary Health Diet, the Mediterranean Diet, and the DASH diet, as well as healthy and unhealthy plant-based diets, those high in ultra-processed foods, those known to promote insulin resistance and inflammation, and healthy and unhealthy low carbohydrate diets — which are often chosen by people looking to lose weight.

A surprise in the study, Xia said, is that one of the unhealthy diets, the unhealthy plant diet —which emphasizes less-healthy plant foods such as french fries — had a slight association with weight loss. That warrants further investigation and the explanation should be interpreted cautiously, Xia said, but is likely because it is low in protein at a time of life — menopause — associated with a loss of muscle, which is a dense tissue.

“Women already lose more muscle, and the low protein intake may make this process quicker,” Xia said.

Xia said she became interested in diet and menopause during her doctoral work on pregnancy, when she noticed how little work was being done about the time when fertility declines. A potential next step, she said, would be a trial where women entering menopause get a dietary intervention to see if it helps weight management and promotes longer term health.