Making small, consistent changes to the types of protein- and carbohydrate-rich foods we eat may have a big impact on long-term weight gain, according to a new study led by researchers at the Friedman School of Nutrition Science & Policy at Tufts University. The results were published on-line in the The American Journal of Clinical Nutrition.
Based on more than 16 years of follow-up among 120,000 men and women from three long-term studies of U.S. health professionals, the authors first found that diets with a high glycemic load (GL) from eating refined grains, starches, and sugars were associated with more weight gain. Previous research has linked GL of the diet, a reflection of how much a food causes a rise in blood glucose, to chronic diseases like type 2 diabetes but it had not been established how GL is related to weight-gain over many years.
Next, the authors determined whether changes in GL impacted the relationship between major protein-rich foods and long-term weight gain.
“There is mounting scientific evidence that diets including less low-quality carbohydrates, such as white breads, potatoes, and sweets, and higher in protein-rich foods may be more efficient for weight loss,” said first and corresponding author Jessica Smith, Ph.D., a visiting scholar at the Friedman School and a research fellow at the Harvard T.H. Chan School of Public Health. “We wanted to know how that might apply to preventing weight gain in the first place.”
Smith and colleagues first looked at the relationship between changes in protein foods and weight gain during every four-years of follow-up. Several key results were seen:
- Increasing intakes of red meat and processed meat were most strongly associated with weight gain.
- Increasing intakes of yogurt, seafood, skinless chicken, and nuts were most strongly associated with weight loss — the more people ate, the less weight they gained.
- Increasing other dairy products, including full-fat cheese, whole milk, and low-fat milk, did not significantly relate to either weight gain or weight loss.
“The fat content of dairy products did not seem to be important for weight gain,” Smith said. “In fact, when people consumed more low-fat dairy products, they actually increased their consumption of carbs, which may promote weight gain. This suggests that people compensate, over years, for the lower calories in low-fat dairy by increasing their carb intake.”
