Many people try to improve their health by following popular diets that focus on cutting carbohydrates or reducing fat.
Low-carb diets often limit foods like bread, rice, and sugar, while low-fat diets reduce oils, butter, and fatty meats.
For years, experts have debated which approach is better for heart health. A new long-term study suggests that this may be the wrong question. What truly matters is not how much fat or carbohydrate you cut, but the kinds of foods you choose to replace them with.
Heart disease remains one of the leading causes of death worldwide. Coronary heart disease happens when the blood vessels that supply the heart become narrowed or blocked by fatty deposits.
This can lead to chest pain, heart attacks, or even sudden death. Because diet plays a major role in cholesterol levels, blood pressure, and inflammation, scientists have long searched for the best eating pattern to reduce risk.
The new research, published in the Journal of the American College of Cardiology, followed nearly 200,000 adults in the United States for more than 30 years. This makes it one of the largest and longest studies ever conducted on diet and heart health.
Participants included nurses and health professionals who regularly reported what they ate, allowing researchers to track long-term patterns. Over the decades, more than 20,000 cases of coronary heart disease were recorded.
When scientists examined the data, they found that both low-carbohydrate and low-fat diets could be linked to better heart health—but only when the diets were built from nutritious foods.
People who focused on vegetables, fruits, whole grains, beans, nuts, and healthy oils had a lower risk of heart disease, even if their diet was low in carbs or low in fat. These foods provide fiber, vitamins, minerals, and beneficial fats that support the heart and reduce inflammation.
In contrast, diets that replaced carbs or fat with processed foods, refined grains, sugary products, and large amounts of red or processed meat were linked to a higher risk of heart disease.
In other words, cutting carbs but eating more bacon and butter did not help. Similarly, cutting fat but replacing it with sugary snacks and white bread also did not protect the heart. The quality of the food made the difference.
The study also measured markers of metabolic health, such as blood fats and inflammation levels. People who followed healthier versions of these diets had lower triglycerides, higher levels of protective HDL cholesterol, and less inflammation in the body. These changes are known to reduce the risk of heart disease over time.
In reviewing the findings, it becomes clear that focusing only on numbers like grams of fat or carbohydrates can be misleading. The body responds not just to nutrients but to whole foods and eating patterns.
A diet rich in plant-based foods appears to support heart health regardless of whether it is labeled low-carb or low-fat. This suggests that people can choose an eating style that fits their preferences while still protecting their health, as long as they prioritize natural, minimally processed foods.
However, the study also has limitations. Participants reported their own diets, which may not always be perfectly accurate. Most were health professionals who may have healthier habits than the general population.
In addition, the research did not focus on extreme diets such as very strict ketogenic plans. Despite these limits, the long follow-up period and large number of participants give the findings strong credibility.
Overall, the study shifts the conversation away from arguing about which diet is superior. Instead, it highlights a simple but powerful message: eating more whole, nutrient-rich foods and fewer processed items is one of the most reliable ways to protect the heart.
Whether someone prefers fewer carbs or less fat, choosing high-quality foods can make a meaningful difference in long-term health.
If you care about heart health, please read studies about top foods to love for a stronger heart, and why oranges may help fight obesity, diabetes, and heart disease.
For more health information, please see recent studies about simple guide to a 7-day diabetes meal plan, and why you should add black beans to your plate.
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