Harvard Scientists Find That Weight Loss Isn’t Always Good

Weight loss is beneficial for obese individuals but not for lean people.

According to a study of over 200,000 people, intentionally losing weight can bring long-term health benefits for individuals with obesity regardless of the approach or strategy used. Those who dropped more than 4.5kg (10 pounds) gained less weight long-term and had a reduced risk of type 2 diabetes than those who did not lose weight. However, lean people did not benefit, with weight loss attempts linked to longer-term weight gain and greater risks of type 2 diabetes. The study was recently published in the journal PLOS Medicine.

Obesity may increase the risk of diseases such as type 2 diabetes. Although long-term weight change and the likelihood of acquiring type 2 diabetes are not fully understood, controlling weight may be a useful strategy for preventing and managing obesity and associated disorders.

Qi Sun and colleagues from the TH Chan Harvard School of Public Health in the United States analyzed healthy individuals from three prospective cohort studies conducted between 1988 and 2017. They ranged in age from 24 to 78, with 11.6% and 14.2% of the cohorts’ members being male. They classified weight reduction techniques that resulted in a loss of more than 4.5 kg into seven groups: low-calorie diet, exercise, low-calorie diet + exercise, fasting, commercial weight loss program, diet pills, and a combination of fasting, commercial, and diet pills (FCP).

Exercise was most effective for long-term weight control and prevention in individuals with obesity and associated with the least weight gain after four years — 4.2% overall average less weight than at the start in individuals with obesity, 2.5% weight loss in overweight, and 0.4% in lean people. This was inverted for FCP, which saw individuals with obesity sustaining 0.3% weight loss, overweight people sustaining 2% more weight gain, and lean individuals with 3.7% more weight gain.

24 years later, the risk of diabetes was reduced for individuals with obesity irrespective of weight loss strategy – ranging from a 21% reduction for exercise to a 13% reduction for diet pills. For overweight individuals, the researchers saw a range of 9% reduction in type 2 diabetes risk for exercise to an increase of 42% risk for those who took pills, and in lean individuals, all weight loss was associated with an increased risk of type 2 diabetes — ranging from a 9% increase for exercise and a 54% increase for pills or FCP.

The authors conclude that while weight loss can be beneficial for those who are overweight and obese, weight loss strategies do not bring the same gains for lean individuals and weight loss strategies should be used only by those who medically need them.

“We were a bit surprised when we first saw the positive associations of weight loss attempts with faster weight gain and higher type 2 diabetes risk among lean individuals,” Sun adds. “However, we now know that such observations are supported by biology that unfortunately entails adverse health outcomes when lean individuals try to lose weight intentionally. The good news is that individuals with obesity will clearly benefit from losing a few pounds and the health benefits last even when the weight loss is temporary.”

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