Harvard study reveals low-carb diet that leads to most weight loss

New Harvard research has found that not all trendy low-carb diets are equal when it comes to maintaining weight — some may even make you gain a few pounds.

People who consume low-carb diets that emphasize plant-based proteins and healthy fats have a better chance of keeping excess weight gain at bay than those who eat low-carb diets comprised mostly of meat and unhealthy fats, according to results of a decades-long study published Wednesday in JAMA Network Open.

“Our study goes beyond the simple question of, ‘To carb or not to carb?’ ” lead study author Binkai Liu, a research assistant in the university’s Department of Nutrition, said in a statement.

“It dissects the low-carbohydrate diet and provides a nuanced look at how the composition of these diets can affect health over years, not just weeks or months,” she explained.

More than 123,300 healthy adults self-reported their diets and weights every four years.

Carbs represented 38% to 40% of the daily calorie intake in each of the five diets studied:

• Total low-carbohydrate diet, which emphasizes overall lower carb intake
• Animal-based low-carbohydrate diet, featuring animal-based proteins and fats
• Vegetable-based low-carbohydrate diet, focused on plant-based proteins and fats
• Healthy low-carbohydrate diet, consisting of plant-based proteins, healthy fats, and fewer refined carbs
• Unhealthy low-carbohydrate diet of animal-based proteins, unhealthy fats, and carbs from sources such as processed breads and cereals

Participants who adhered more to the total low-carb, animal-based, or unhealthy low-carb diets on average gained more weight compared to those who partook in the healthy low-carb diet.

Liu told CNN that the unhealthy low-carb dieters gained, on average, 5.1 pounds over four years.

The healthy low-carb dieters, meanwhile, lost an average of 4.9 pounds over the same period.

The weight differences were most pronounced among participants who were younger than 55, overweight or obese, and/or less physically active.

The vegetable-based low-carb diet, meanwhile, offered mixed results.

“The key takeaway here is that not all low-carbohydrate diets are created equal when it comes to managing weight in the long-term,” senior author Qi Sun, associate professor in the nutrition department, said in a statement.

Sun continued: “Our findings could shake up the way we think about popular low-carbohydrate diets and suggest that public health initiatives should continue to promote dietary patterns that emphasize healthful foods like whole grains, fruits, vegetables, and low-fat dairy products.”