Looking for a snack to keep you on track to lose or maintain weight? Reach for the nuts, says a Harvard study released last month in the online journal BMJ Nutrition, Prevention & Health. (Two of the authors were partly funded by the Peanut Institution and the California Walnut Commission. "The funders have no roles in study design, data collection and interpretation, and decision on manuscript publication," the researchers wrote.)
The research looked at self-reported dietary habits in over 289,000 Americans, men and women, across a span of 24 years. (Though the group was large, the researchers pointed out that participants were mostly white and of higher socioeconomic status.) Every four years, the participants were asked to state their weight and how often they'd eaten a serving of nuts over the past year. Participants across the board had an average weight gain of 0.32 kilograms (0.71 pounds) per year. But for those who ate at least half a serving of nuts per day, the risk of weight gain was lower: they avoided an average of .74 extra kilograms (1.6 pounds) over four years and had a 16 percent lower chance of becoming obese, the study found. Participants also gained less weight when they swapped foods like French fries, chips, dessert, and processed meats for nuts.
Researchers looked at all types of nuts: peanuts as well as all types of tree nuts, which include walnuts, almonds, cashews, hazelnuts, pistachios, and pecans. They even tracked peanut butter intake, but (sadly) didn't find the same correlation to avoiding weight gain.
The study was observational, which means that researchers can't completely prove that the nuts alone were the cause of the positive findings. These results, though, fall in line with previous studies on the effect of nuts on weight gain. The obvious question becomes: why are nuts effective at helping to prevent extra weight gain?
The research team offered up a couple of potential answers. Your body digests fat more slowly than other nutrients, for one thing, which means it keeps you feeling full for longer. Nuts are also high in fiber and bind well to fats in your gut, which allows your body to excrete more calories.
There are a lot of factors that determine how much weight you gain or lose throughout your life, some of which you can't exactly control, such as your age and hormones. Still, your diet (and exercise habits) certainly have a lot to do with it, and choosing healthy, whole foods will only do your body good in terms of how you weigh and how you feel. Can nuts help with that? Potentially, and since just half a serving (1/8 of a cup!) will start to give you some benefits, it might be worth a try.