Potato harvest by lisibo on flickr

A new study published last week in the New England Journal of Medicine linked potatoes to longterm weight gain. But it also said other things. The journalists’ reports of the study focus on the potatoes. It is true that the study team certified a slightly stronger link between potatoes and weight gain than between, for example, soda and extra pounds.

But the study also concluded this: People who exercise lose weight. The link between exercise and weight loss was stronger than the link between potatoes and weight gain.

I am so tired of Americans blaming particular foods or categories of food for weight gain. The study and other articles by Harvard nutrition experts hammer home that moving around combined with eating good food are both vital to keeping weight down.

Because Americans crave fads more than we crave potato chips, we seize upon each new nutrition study, praying that it will list evil foods that we can just rule out. We then fight about the new list of evil foods while talking to friends at parties. The new study has delivered! It has given us something new to fight about at parties. It has told us what we already know. Don’t eat a giant bag of potato chips.

The study said much, much more. It has told us that we ought to exercise.

After college people tend to gradually stop moving around. They gain a few pounds each year because it’s hard to schedule the time to exercise. They battle diseases, back troubles, long commutes, and loving relatives who hand them giant bratwurst sandwiches. Adult life in America resembles a dangerous trip down the Amazon, except it’s the supermarket aisle. Instead of alligators we ward off cookies and chips and entire aisles of soda.

So before we completely give up potato chips, we ought to get some exercise.

Here is what the Boston doctors’ study said, taken right off the New England Journal of Medicine web site. I have bold-faced some phrases.


“Specific dietary and other lifestyle behaviors may affect the success of the straightforward-sounding strategy ‘eat less and exercise more’ for preventing long-term weight gain.

“We performed prospective investigations involving three separate cohorts that included 120,877 U.S. women and men who were free of chronic diseases and not obese at baseline, with follow-up periods from 1986 to 2006, 1991 to 2003, and 1986 to 2006. The relationships between changes in lifestyle factors and weight change were evaluated at 4-year intervals, with multivariable adjustments made for age, baseline body-mass index for each period, and all lifestyle factors simultaneously. Cohort-specific and sex-specific results were similar and were pooled with the use of an inverse-variance–weighted meta-analysis. “Within each 4-year period, participants gained an average of 3.35 lb (5th to 95th percentile, −4.1 to 12.4). On the basis of increased daily servings of individual dietary components, 4-year weight change was most strongly associated with the intake of potato chips (1.69 lb), potatoes (1.28 lb), sugar-sweetened beverages (1.00 lb), unprocessed red meats (0.95 lb), and processed meats (0.93 lb) and was inversely associated with the intake of vegetables (−0.22 lb), whole grains (−0.37 lb), fruits (−0.49 lb), nuts (−0.57 lb), and yogurt (−0.82 lb) (P≤0.005 for each comparison). Aggregate dietary changes were associated with substantial differences in weight change (3.93 lb across quintiles of dietary change). Other lifestyle factors were also independently associated with weight change (P<0.001), including physical activity (−1.76 lb across quintiles); alcohol use (0.41 lb per drink per day), smoking (new quitters, 5.17 lb; former smokers, 0.14 lb), sleep (more weight gain with <6 or >8 hours of sleep), and television watching (0.31 lb per hour per day).”

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