Not Losing Weight? Study Finds Healthy Diet May Still Bring Major Health Gains

A new study published in the European Journal of Preventive Cardiology reveals that nearly one-third of individuals who followed a healthy diet did not lose weight, yet still experienced significant improvements in key cardiometabolic health markers.

The study focused on 761 adults with abdominal obesity who participated in three long-term workplace-based nutrition clinical trials—DIRECT, CENTRAL, and DIRECT-PLUS—in Israel. Participants were randomly assigned to follow various healthy dietary patterns, including low-fat, low-carbohydrate, Mediterranean, and Green-Mediterranean diets for 18 to 24 months. High adherence and comprehensive metabolic profiling made these trials particularly robust.

Despite following their assigned diets, 28% of participants did not lose any weight or even gained some. However, these “weight loss-resistant” individuals still saw notable health improvements, including increased levels of HDL (good) cholesterol, lower leptin levels—suggesting improved hunger signaling—and a reduction in visceral fat, the harmful fat stored deep in the abdomen.

While the study was predominantly male, researchers emphasize the need for future trials focused more on women to better understand gender-specific responses.

The study also uncovered a groundbreaking biological insight: Using advanced omics tools, researchers identified 12 specific DNA methylation sites that strongly predict long-term weight loss success.

“This novel finding shows that some people may be biologically wired to respond differently to the same diet,” said corresponding author Iris Shai principal investigator of the nutrition trials and adjunct professor of nutrition at Harvard Chan School. “This isn’t just about willpower or discipline—it’s about biology.”

These findings highlight that meaningful health improvements can occur without weight loss—offering a new, more inclusive definition of dietary success.

Reference: Anat Yaskolka Meir, Gal Tsaban, Ehud Rinott, Hila Zelicha, Dan Schwarzfuchs, Yftach Gepner, Assaf Rudich, Ilan Shelef, Matthias Blüher, Michael Stumvoll, Uta Ceglarek, Berend Isermann, Nora Klöting, Maria Keller, Peter Kovacs, Lu Qi, Dong D Wang, Liming Liang, Frank B Hu, Meir J Stampfer, Iris Shai, Individual response to lifestyle interventions: a pooled analysis of three long-term weight loss trials, European Journal of Preventive Cardiology, 2025;, zwaf308, https://doi.org/10.1093/eurjpc/zwaf308