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Nuts, Yogurt and Dissecting the Latest Data on Diet

Okay, it may not seem like a huge shock that consuming more potato chips, fries or sugary drinks over the years is associated with weight gain, as a new study finds.

But what about nuts? Traditionally we’d think of them as barriers to weight loss because they’re calorie-dense, Michael Dansinger, an assistant professor of medicine at Tufts University School of Medicine, tells the Health Blog. The study, by Harvard School of Public Health researchers, found that boosting nut consumption over time was actually associated with .57 pounds less weight gain over a four-year period.

Yogurt, too, was a bit of a surprise: eating more was associated with .82 pounds less weight gain. (The study didn’t separately evaluate yogurts with different levels of fat or sweeteners.)

What’s going on? It’s possible that there’s some causative effect with certain foods.  Nuts, for example, may be more filling, crowding out other less-satisfying high-calorie foods and making you eat less overall. And the bacteria in yogurt, the study authors write, might possibly play a role in weight changes. (Gut bacteria have been hypothesized to influence obesity.)

It’s also possible that people who eat yogurt or nuts are more likely to do something else that keeps their weight down, but that study authors didn’t identify and control for. (Researchers did control for  physical activity, TV-watching and a host of other dietary and lifestyle factors.) “Yogurt may be a marker for a healthy lifestyle,” says Dansinger.

These types of large, observational studies aren’t ideal for really teasing out whether yogurt causes weight loss — or, for that matter, whether potato chips actually cause weight gain (1.69 pounds every four years for every extra daily serving, the study found) or are just a marker for a generally bad diet. That’s a job for more targeted studies, though a randomized trial giving one group of people daily potato chips to see if they get fatter than the chip-deprived seems pretty unlikely.

Instead, with this study,  “you have to look at the big picture,” Linda Van Horn, a professor of preventive medicine at Northwestern University’s Feinberg School of Medicine, tells the Health Blog. “It documents the fact that, yes, non-nutritionally dense foods like sugar-sweetened beverages, like chips, like fries, truly contribute extra calories that go beyond what average sedentary people really need in this day and age,” she says.

“They give people calories that they don’t need and prevent them from [getting] nutrients they do need. The combination is really unfortunate,” she says.

Avoiding that combination seems like a fairly sensible step.

Image: iStockphoto

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