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  • A new study found that people with obesity who lost weight had a significantly lower risk of type 2 diabetes.
  • However, when lean people attempted to lose weight, their risk of type 2 diabetes increased.
  • The researchers studied the health data of nearly 200,000 people from three prospective cohort studies conducted between 1988 and 2017.

Weight loss is much more beneficial for people with excess weight compared to individuals who are already lean, according to new research.

The study, which published in PLOS Medicine Tuesday, evaluated weight loss strategies and their health effects in nearly 200,000 people and found that people with obesity who lost weight had a significantly lower risk of type 2 diabetes, however, when lean people attempted to lose weight, their risk of type 2 diabetes increased.

Bariatric physicians were surprised to learn that weight loss strategies had such opposite health effects on people depending on their body mass index (BMI) at baseline.

They suspect that underlying biological differences impact how and why people’s bodies respond differently to weight loss efforts.

“The main takeaway is that weight loss is beneficial for those who are overweight; lean individuals did not experience the same or more benefit,” Dr. Mir Ali, a bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, told Healthline.

Ali was not involved in the study.

The researchers studied the health data of nearly 200,000 people from three prospective cohort studies conducted between 1988 and 2017.

People were deemed lean if they had a BMI under 25. If it was 25 to 30 they were deemed as having overweight and if it was above 30 they were deemed as having obesity.

The team evaluated various weight-loss strategies — including a low-calorie diet, exercise, low-calorie diet and exercise, fasting, a commercial weight loss program (CWLP), and diet pills — in people who lost at least 4.5 kilograms, or about 10 pounds.

They also looked at people who did not lose weight.

Of the people who lost at least 4.5 kilograms team found that all of the weight-loss strategies were associated with less weight gain and a lower risk of diabetes among people who have obesity at baseline, however, exercise was the most effective strategy.

“The primary determinant for success in obtaining and sustaining weight loss is exercise capacity. This study and many others support this fact once again,” says Dr. David Prologo, a board-certified obesity medicine physician, who was not involved with the study.

Over the course of 24 years, people with obesity who exercised had a 21% lower risk of diabetes and those who took diet pills had a 13% lower risk. People, who have overweight and who exercised, had a 9% lower risk of Type 2 diabetes and those who took diet pills had a 42% higher risk of diabetes.

“If you are overweight or obese, even moderate weight loss — up to 4.5% — showed pretty significant gains in overall health and reduction in disease risk,” says Dr. Dana Ellis Hunnes, a senior clinical dietitian at UCLA medical center, assistant professor at UCLA Fielding school of public health, and author of Recipe for Survival.

The health effects were opposite among lean people, and according to the study, lean people who intentionally lost weight tended to gain back more weight and have a higher risk of diabetes.

Lean people who exercised in order to lose weight had a 9% greater risk of diabetes and lean individuals who took diet pills or followed a commercial weight loss program to lose weight had a 54% increased risk of diabetes.

“These findings are surprising because it would seem that weight loss would be beneficial for everyone; based on this study, lean individuals seem to have a different biological makeup,” Ali said.

Obesity causes hormonal and metabolic complications that can contribute to a range of health problems, including type 2 diabetes, insulin resistance, hypertension and heart disease.

Hunnes said the risk of diabetes and other health issues can increase depending on a person’s weight.

When people, who have obesity, lose weight they eliminate some of the fatty tissue that produces inflammation, disrupts hormonal production, and contributes to insulin resistance.

“Decreasing the volume of that tissue directly results in improved health,” says Prologo.

Lean individuals, on the other hand, have a different hormonal and metabolic makeup, which likely causes them to respond different to weight loss.

When you are lean”trying to lose weight can actually have negative effects on your overall metabolism, mental health, and possibly even overall health as you increase the likelihood you’re going to be hungry and eat more and possibly gain weight,” says Hunnes.

People who are already lean should engage in maintenance activities, says Prologo. This could include activities such as exercise and eating nutrient-dense whole foods while eliminating or reducing the consumption of ultra-processed foods.

Ali says he often sees people try weight-loss strategies that aren’t sustainable — most diets will work for a time, he says, but the weight comes right back when the diet ends.

“The key is making dietary and exercise changes that can be maintained long term,” Ali said.

Weight loss is much more beneficial for people with excess weight compared to individuals who are already lean, according to new research. While the mechanisms are unclear, health experts suspect that underlying biological differences impact how people’s bodies respond to weight loss efforts. While even moderate weight loss can lead to significant health gains in people with obesity and overweight, lean people should focus on weight maintenance activities rather than weight loss strategies.