The research team, led by Binkai Liu from the Department of Nutrition at the Harvard TH Chan School of Public Health, analyzed data from 123,332 healthy adults over a period spanning 1986 to 2018. These data came from three large American epidemiological studies: the Nurses’ Health Study I and II and the Health Professionals Follow-up Study. Participants, followed every four years, provided information on their diet and weight. The scientists were thus able to compare five types of low-carbohydrate diets, differentiated in particular according to the source of proteins and fats: animal or vegetable. The objective was to evaluate the impact of these diets on long-term weight gain.
Increased effectiveness among those under 55
These beneficial effects are even more marked in participants aged under 55, particularly those who are overweight or obese. Less physical activity also accentuated these differences between diets.
What foods should you choose for an effective diet?
The conclusions, published in the journal JAMA Network Open, are unequivocal: diets based on proteins and fats of plant origin (legumes, whole grains, vegetable oils, fruits, vegetables, etc.) and incorporating unrefined carbohydrates allow less weight gain in the long term. On the other hand, diets rich in animal proteins and fats lead, on average, to greater weight gain.
To maximize the benefits of a low-carb diet, researchers recommend consuming:
- Legumes : lentils, chickpeas, broad beans, beans;
- Whole grains : quinoa, brown rice, wholemeal bread;
- Fresh fruits and vegetables : rich in fiber and antioxidants;
- Soy products : tofu, tempeh;
- Vegetable oils : olive, rapeseed, walnut oil;
- Nuts : almonds, walnuts, hazelnuts;
- Low-fat dairy products.
These recommendations are in line with those of the National Nutrition and Health Program (PNNS) in France, which also emphasizes a diet rich in natural products, associated with regular physical activity.
A nuanced warning
Despite these promising results, the researchers highlight certain limitations. Participants in the Nurses’ Health Study II were the only ones to report a significant reduction in weight gain with a diet based on plant proteins. This shows that further work is needed to refine these conclusions.
“Not all low-carb diets are equal when it comes to long-term weight management. Promoting healthy foods like whole grains, fruits and vegetables must remain a public health priority“, concludes the study.