Study Finds Diet and Exercise Improve Metabolic Health Even Without Weight Loss

New Delhi: Losing weight isn’t the only way to get healthier. A new international study has found that even people who don’t shed kilos after switching to a healthy lifestyle still experience significant health benefits.

The research, published on June 5 in the European Journal of Preventive Cardiology, was led by scientists at Harvard T.H. Chan School of Public Health and Ben-Gurion University in Israel.

It tracked 761 adults with abdominal obesity over 18 to 24 months as part of three workplace-based clinical trials in Israel—DIRECT, CENTRAL, and DIRECT-PLUS.

All participants were assigned to follow one of several healthy diets, including low-fat, low-carbohydrate, Mediterranean, or green-Mediterranean plans. They also had access to gyms and received exercise guidance.

At the end of the trials, nearly one-third of participants, about 28% were considered "weight loss resistant," meaning they did not lose weight or even gained some, despite following the programme closely. Still, they showed improvements in key health markers.

Independent of weight change, these individuals saw higher levels of HDL (good) cholesterol, lower levels of leptin (a hormone that regulates hunger), and reductions in visceral fat, a type of belly fat linked to increased risk of disease.

"We have been conditioned to equate weight loss with health, and weight loss-resistant individuals are often labelled as failures," said lead author Anat Yaskolka Meir, postdoctoral research fellow in the Department of Epidemiology at Harvard Chan School. "Our findings reframe how we define clinical success. 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."

Overall, 36% of participants achieved clinically significant weight loss (losing more than 5% of their starting weight), another 36% had moderate weight loss (up to 5%), and 28% saw no weight loss.

Weight loss did result in additional benefits. The study found that for every kilogram lost, there was a 1.44% increase in HDL cholesterol, a 1.37% drop in triglycerides, a 2.46% reduction in insulin, a 2.79% decrease in leptin, and a 0.49-unit reduction in liver fat. Improvements were also seen in blood pressure and liver enzymes.

However, researchers emphasized that even without weight loss, many participants experienced deep metabolic improvements.

"These are deep metabolic shifts with real cardiometabolic consequences," said Yaskolka Meir. "Our study showed that a healthy diet works, even when weight doesn’t shift."

The study also used advanced omics tools and identified 12 DNA methylation markers that strongly predict long-term weight loss.

"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. And now we’re getting close to understanding it."

The researchers noted that most of the participants were men, and future studies should focus more on women to better understand gender differences in weight loss and metabolic response.

The findings highlight that health improvements can occur without weight loss, offering a new perspective on how success is measured in nutrition and lifestyle interventions.