A daily serving of nuts may prevent weight gain and improve metabolic health in the long run, two new studies suggest.
Nuts are packed with unsaturated fatty acids, fiber, protein, and other beneficial chemicals, which may all contribute to good health.
However, can nuts aid weight loss? Are certain types of nuts better able to support good metabolism?
The first study — led by Xiaoran Liu, Ph.D., a research associate in the nutrition department of the Harvard T.H. Chan School of Public Health in Boston, MA — looked at the long-term effects of nuts and peanuts on body weight.
The second study examined the effects of Brazil nuts on satiety, blood sugar, and insulin response.
It was supervised by Mee Young Hong, Ph.D., a registered dietician and a professor in the School of Exercise & Nutritional Sciences at San Diego State University in California.
Nuts prevent weight gain in adulthood
The first study explored nut consumption in:
- 25,394 healthy men who had taken part in the Health Professionals Follow-up Study
- 53,541 women who had participated in the Nurses' Health Study
- 47,255 women who had taken part in the Nurses' Health Study II
The three groups had filled in food frequency questionnaires once every 4 years.
The researchers discovered that replacing foods that had less nutritional value with a 1-ounce serving of nuts and peanuts lowered the risk of weight gain and obesity over the 4-year follow-up intervals.
More specifically, replacing a serving of red meat, processed meat, french fries, desserts, or potato chips with a serving of nuts correlated with significantly less weight gain in the long run.
The study's first author comments on the findings, saying, "People often see nuts as food items high in fat and calories, so they hesitate to consider them as healthy snacks, but they are in fact associated with less weight gain and wellness."
"Once people reach adulthood, they start to gradually gain about 1 pound a year of weight, which seems small. But if you consider gaining one pound over 20 years, it accumulates to a lot of weight gain," Liu notes.
"Adding 1 ounce of nuts to your diet in place of less healthy foods — such as red or processed meat, french fries or sugary snacks — may help prevent that slow, gradual weight gain after you enter adulthood and reduce the risk of obesity-related cardiovascular diseases."
Xiaoran Liu, Ph.D.
Brazil nuts benefit insulin, glucose responses
In the second study, researchers examined the effects of consuming Brazil nuts in 22 healthy adult participants, 20 of whom were women.
The participants added either 36 grams of pretzels or 20 grams of Brazil nuts to their normal diet in two trials. At least 48 hours passed between trials.
The Brazil nuts and pretzels contained about the same number of calories and the same amount of sodium. Both triggered a sense of fullness, but the Brazil nuts contributed to an increased feeling of satiety.
Forty minutes after the participants had consumed their snacks, the researchers found that the pretzels had caused significant increases in blood sugar and insulin levels, whereas the Brazil nuts had not.
The study's senior author explains, "While both Brazil nuts and pretzels increased a sense of fullness after they were eaten, eating Brazil nuts stabilized postprandial (after eating) blood glucose and insulin levels, which may be beneficial in preventing diabetes and weight gain."
Although the study was observational, the researchers speculate that selenium may explain the benefits of Brazil nuts. Prior studies had linked the mineral with better insulin and blood sugar responses, and Brazil nuts are rich in selenium.
However, the researchers caution that because only 9 percent of participants were men, the study's findings may not apply to all.
"Our study allows researchers and clinicians to consider the possible beneficial role of Brazil nuts to help people feel full and maintain a healthy level of glucose, reducing the risk of obesity and diabetes."
Mee Young Hong, Ph.D.