A new study published in the European Journal of Preventive Cardiology reveals that following a healthy diet yields significant health benefits—even if it does not lead to weight loss. Researchers found that while only about one-third of individuals experienced long-term weight loss, those who either lost a moderate amount of weight or were resistant to weight loss still showed important improvements in cardiometabolic health. These benefits included reduced visceral fat, higher levels of high-density lipoprotein (HDL), and lower leptin levels.
Traditionally, weight loss has been equated with health improvements, often labeling individuals who do not lose weight as failures. However, Anat Yaskolka Meir, PhD, postdoctoral fellow at Harvard Chan School’s Department of Epidemiology, emphasized, “People who do not lose weight can improve their metabolism and reduce their long-term risk for disease. That’s a message of hope, not failure.”
The study pooled data from three major long-term weight loss trials: DIRECT, CENTRAL, and DIRECT PLUS. Each trial evaluated different dietary approaches, including low-fat, low-carbohydrate, Mediterranean, and green-Mediterranean diets, and measured various outcomes related to body composition, cardiovascular health, metabolic function, and inflammation.
Key findings from the combined data (totaling over 700 participants) include:
- Weight loss-resistant individuals (no significant weight loss) showed improvements in HDL cholesterol and reductions in visceral and liver fat, despite some increases in total cholesterol and inflammatory markers.
- Moderate weight loss (up to 5%) was associated with better waist circumference, blood pressure, lipid profiles, insulin sensitivity, inflammation markers, and liver health.
- Successful weight loss (>5%) led to the most significant improvements in these health indicators, with the exception of low-density lipoprotein cholesterol and fasting plasma glucose, which did not improve as much.
Furthermore, the study quantified the benefits per kilogram lost, showing each kilogram corresponded to a 1.44% increase in HDL cholesterol, a 1.37% decrease in triglycerides, a 2.46% decrease in insulin, a 2.79% decrease in leptin, and a 0.49-unit reduction in liver fat.
Iris Shai, PhD, principal investigator and adjunct professor at Harvard Chan School, noted that these results highlight biological differences in how individuals respond to the same diet, underscoring that health improvements are not solely about willpower but also biology.
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