Healthy low carb and low fat diets can lower heart disease risk, study finds

New research suggests that the quality of a low-carbohydrate or low-fat diet may matter more for heart health than simply the amount of fat or carbs consumed.

Published February 11 in the Journal of the American College of Cardiology, the study analyzed data from nearly 200,000 participants across three large, long-term studies, with more than 30 years of follow-up. 

During that time, researchers documented 20,033 cases of coronary heart disease (CHD).

The study found that “healthy” low-carb and low-fat diets that are rich in plant-based foods, whole grains, and unsaturated fats were associated with a significantly lower risk of CHD. In contrast, “unhealthy” versions high in refined carbohydrates, animal fats, and processed proteins were linked to a higher risk.

Zhiyuan Wu, a postdoctoral fellow at Harvard T.H. Chan School of Public Health and lead author, said: “It’s not simply about cutting carbs or fat, but about the quality of foods people choose to construct those diets. Focusing only on nutrient compositions but not food quality may not lead to health benefits.”

Experts not involved in the study stressed the findings’ significance. Oana Penciu, MD, a cardiologist at Keck Medicine of USC, said the research resolves years of conflicting data. “Healthy versions of both diets emphasizing plant-based proteins, unsaturated fats, and whole grains provide similar protective benefits. The source of your food matters far more than the label attached to it,” she told Healthline.

Diet quality affects key cardiovascular markers. Participants who followed healthier dietary patterns showed lower levels of inflammation, lower triglycerides, and higher HDL cholesterol, all factors linked to reduced heart disease risk.

Cardiologists also emphasized the importance of tailored approaches. Cheng-Han Chen, MD, of MemorialCare Saddleback Medical Center, recommended diets rich in plant-based foods, nuts, whole grains, and lean protein, and low in sodium, saturated fat, and processed carbohydrates. 

“The quality of your diet affects the degree of inflammation in your body, further influencing your risk of heart disease,” he said.

Both low-carb and low-fat diets can support cardiometabolic health. Bariatric surgeon Mir Ali, MD, noted that low-fat diets may benefit individuals with high cholesterol, while low-carb diets can aid weight loss. “Recommendations must be tailored to the individual after a close clinical evaluation,” he added.

The American Heart Association continues to recommend dietary patterns emphasizing fruits, vegetables, whole grains, healthy proteins, and minimally processed foods. 

Experts advise focusing on real, balanced foods rather than obsessing over macronutrient counts. Penciu said: “Small, steady improvements add up. Consistency and quality matter more than perfection.”