Share on PinterestRecent research shows that diet quality may help improve overall health more than just counting calories. fcafotodigital · E+/GettyA two-year study found that a Mediterranean-style diet and a calorie-focused weight loss program led to similar amounts of weight loss.People following the Mediterranean-style diet saw greater improvements in diet quality and were more likely to say they would recommend the program.Experts say calorie balance remains important for weight loss, while choosing higher-quality foods can provide additional benefits for overall health.
A two-year study tested a Mediterranean-style diet adapted for the Southern U.S. (Med-South) against a calorie-focused program.
While both groups lost a similar amount of weight, the Med-South group saw a greater improvement in overall diet quality.
The study, recently published in JAMA Network Open, highlights how different approaches to weight loss may affect diet quality and long-term adherence.
The study followed 360 individuals from North Carolina primary care practices who had a BMI of 30 or greater and an average age of 55. Most participants also had multiple chronic conditions, such as diabetes and hypertension.
Participants were randomly assigned to one of two groups: a Mediterranean-style diet (Med-South) or a control weight-loss program. There were 182 in the Mediterranean diet group and 178 in the control group.
The study lasted 24 months, with assessments at 4, 12, and 24 months.
The Mediterranean diet intervention included three phases:
Phase 1 (months 1-4): focused on improving diet qualityPhase 2 (months 5-12): focused on weight lossPhase 3 (months 13-24): focused on weight loss maintenance
The control intervention provided access to the workshop and digital components of the WeightWatchers program.
The Mediterranean-style diet program was led by registered dietitians and emphasized healthy fats, whole grains, fruits, and vegetables, while limiting processed foods and refined carbs.
The WeightWatchers program focused primarily on cutting calories, while encouraging more fruits and vegetables.
At the end of 24 months, both groups showed similar average weight loss: 3.4% in the Mediterranean-style group and 3.5% in the control group.
The researchers also found no significant differences between the groups in outcomes such as blood pressure.
Christopher Gardner, PhD, professor of medicine at Stanford Prevention Research Center, who wasn’t involved in the study, noted, “The quality of the diets was a secondary outcome, not the primary outcome. The study was not designed to test that. It can be interesting to look at that, but if quality is the main question of interest, the study has to be designed to specifically test that.”
While both groups lost a similar amount of weight after 24 months, the Mediterranean diet group showed significantly greater improvements in overall diet quality, including greater consumption of nuts, vegetable oils, whole grains, non-starchy vegetables, and fruit.
It has also been associated with a reduced risk of cardiovascular disease, stroke, diabetes, and dementia.
During the study, 95% of the Mediterranean-style group said they would recommend the program, compared with 68% of the control group.
A 2024 trial, DIETFITS, also found that high dietary adherence combined with high diet quality led to the greatest weight loss; neither alone was sufficient.
This suggests that following an eating plan you can stick with is important, but diet quality may also play a role in supporting weight loss and overall health.
“A main concept I work with my patients on is the importance of quality over quantity. Though weight loss may be achieved on a lower-calorie diet, the results may not be sustained long term, and the potential loss of nutrients over time could impact overall chronic disease risk and mortality,” Kristin Kirkpatrick, President of KAK, Consulting, LLC, and a dietitian at the Cleveland Clinic Department of Wellness & Preventive Medicine in Cleveland, Ohio, told Healthline. Kirkpatrick wasn’t involved in the study.
“This study follows the same insight that a high quality diet can beneficially impact not only weight loss success but overall health outcomes as well,” she added.
Higher diet quality can also provide additional health benefits, such as:
However, if you are trying to lose weight, calorie balance is still important. Higher-quality foods can make it easier to manage calories, but calories still matter.
“Weight loss is typically achieved by a prolonged period of calorie restriction. It is possible to eat nothing but junk food and lose weight if the amount of total food consumed does not meet the caloric needs of the person,” said Gardner.
“However, losing weight while choosing higher quality foods (defined by a higher intake of the vitamins and minerals necessary for a healthy metabolism) supports better overall health, in the long term.”