A new study has found that individuals who follow a healthy diet can experience significant improvements in cardiometabolic health—even if they do not achieve substantial weight loss.
Published in the European Journal of Preventive Cardiology, the study revealed that only one-third of participants achieved long-term weight reduction. However, those who experienced only modest weight loss—or showed resistance to weight change—still saw measurable improvements in internal fat levels and markers of metabolic health, such as increased HDL cholesterol and reduced levels of leptin, a hormone linked to fat storage.
“We’ve long equated weight loss with better health, and people who don’t lose weight are often seen as having failed,” said Dr. Anat Yaskolka Meir, a postdoctoral fellow at Harvard T.H. Chan School of Public Health, in a statement. “But our findings redefine what clinical success looks like. Even without losing weight, people can improve their metabolism and lower long-term health risks. This offers hope—not failure.”
A New Look at Diet and Metabolic Health
The study pooled data from three large-scale dietary intervention trials: DIRECT, CENTRAL, and DIRECT PLUS. Each trial examined the impact of different dietary approaches—ranging from low-fat and low-carbohydrate diets to Mediterranean and green-Mediterranean diets—on weight loss and various metabolic outcomes.
The DIRECT trial compared low-fat, low-carb, and Mediterranean diets, measuring outcomes like weight change and cardiovascular markers.
The CENTRAL study examined how dietary strategies affect body fat distribution and metabolism over time. It included assessments of lipid profiles, glucose control, liver enzymes, inflammation, and genetics.
The DIRECT PLUS trial evaluated long-term effects of traditional and green Mediterranean diets on abdominal fat, liver fat, cognitive function, heart health, and other physiological markers.
Results Across Different Weight Categories
In a combined analysis of all three trials, researchers classified 761 participants into three groups:
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Resistance to weight loss (212 individuals)
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Moderate weight loss (277 individuals, with <5% reduction in body weight)
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Successful weight loss (272 individuals, with ≥5% reduction)
Those who resisted weight loss were more likely to be older women, with smaller initial waist circumference and lower liver enzyme levels. Despite limited changes in body weight, this group still experienced health improvements, including reductions in visceral and liver fat, and increases in HDL (“good”) cholesterol. However, some risk markers—including total cholesterol, fasting glucose, triglycerides, and C-reactive protein—also increased in this group.
Participants who experienced moderate weight loss showed improvements in waist size, systolic blood pressure, HDL cholesterol, triglycerides, insulin levels, insulin resistance (HOMA-IR), inflammation markers (CRP), liver function, and fat accumulation in the abdomen and liver.
Those who lost more than 5% of their initial body weight saw the greatest overall improvements, though changes in LDL cholesterol, total cholesterol, and fasting glucose were less consistent.
Benefits Linked to Even Small Weight Changes
The researchers also found a clear association between small reductions in body weight and improvements in key metabolic markers. For every kilogram of weight lost:
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HDL cholesterol increased by 1.44%
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Triglycerides decreased by 1.37%
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Insulin decreased by 2.46%
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Leptin levels dropped by 2.79%
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Liver fat decreased by 0.49 units
“These findings highlight that individuals may respond differently to the same diet,” said Dr. Iris Shai, principal investigator of the trials and adjunct professor of nutrition at Harvard. “It’s not just about willpower or discipline—it’s about biology. And we’re just beginning to understand how it works.”
Implications for Public Health and Clinical Care
The study suggests that evaluating the success of dietary interventions solely based on weight loss may be too narrow. Even when weight remains stable, following a nutritious diet can still lead to meaningful improvements in metabolic health.
The authors advocate for a broader view of clinical success—one that recognizes improvements in lipid profiles, inflammation, and internal fat distribution as valuable outcomes, regardless of weight change.
This new understanding could influence future dietary guidelines and shift the focus from weight-centric goals to overall health markers, offering a more inclusive and hopeful approach for individuals struggling to lose weight despite healthy habits.
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