A new study into overweight and obesity has found that weight loss is much more beneficial for people with excess weight compared to individuals who are already lean.
The study, by researchers at T.H. Chan Harvard School of Public Health in the United States, evaluated weight loss strategies and their health effects in nearly 200,000 people. They 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 data from three prospective cohort studies conducted between 1988 and 2017 among nearly 200,000 people. 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.
They grouped people into seven categories based on methods used to lose at least 4.5 kilograms — low-calorie diet, exercise, low-calorie diet plus exercise, fasting, commercial weight loss program, diet pills, and a combination of fasting, commercial and diet pills. They also looked at people who did not lose weight. Of the people who lost at least 4.5 kilograms and had obesity at baseline, the team found that all of the weight-loss strategies were associated with less weight gain and a lower risk of diabetes. The study also found that exercise was the most effective strategy for weight loss.
Over the course of the 24-year study period, people with obesity who exercised had a 21 percent lower risk of diabetes and those who took diet pills had a 13 percent lower risk. People who were overweight and exercised, had a 9 percent lower risk of Type 2 diabetes and those who took diet pills had a 42 percent higher risk of diabetes.
The study showed that if you are overweight or obese, even moderate weight loss of up to 4.5 percent led to significant gains in overall health and reduction in disease risk. Surprisingly the health effects were found to be opposite among lean people, with lean people who intentionally lost weight tending to gain back more weight and have a higher risk of diabetes. Lean people who exercised in order to lose weight also had a 9 percent greater risk of diabetes and lean individuals who took diet pills or followed a commercial weight loss program to lose weight had a 54 percent increased risk of diabetes.
Bariatric physicians, who focus on treating those who have obesity and help promote weight loss and increase overall health, 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 surmised that underlying biological differences could be impacting how and why people’s bodies respond differently to weight loss efforts.
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. 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.
Lean individuals, on the other hand, have a different hormonal and metabolic makeup, which likely causes them to respond differently to weight loss. Attempting to lose weight when you are lean can have negative effects on your overall metabolism, mental health, and possibly even overall health.
People who are already lean should aim to engage in maintenance activities such as exercising to stay healthy and eating nutrient-dense whole foods while eliminating or reducing the consumption of ultra-processed foods.