4:07 PM EDT, June 24, 2011
Almost anyone engaged in the battle of the bulging midsection knows that French fries are not their friends. But the real shocker in the study of long-term weight gain that came out of Harvard this week was that eating too many spuds of any kind — even plain old baked potatoes — could make you heavier. Every additional serving of potatoes that people added to a regular diet each day was connected to an average weight gain of about a one pound over four years. That is not a ton of weight gain, but as the study published Thursday in The New England Journal of Medicine points out, it adds up over time.
The goal of this study, which looked at the diets of 120,000 men and women in their 30s, 40s and 50s over 20 years, was to detail how much weight individual foods make them put on or take off. One theory of why eating an extra daily helping of potatoes could make people plumper was that it produces a surge of blood sugar levels in the body. As your body reacts to the surge, you feel hungry and eat more. That effect is certainly familiar to anyone who has polished off a serving of Baltimore's famous deep-fried potato skins. However, it's hard to believe that boiled potatoes have the same allure.
As with most solid scientific research — and these studies, which rely on self-reported data from nurses and health professionals, are highly respected — there were plenty of caveats. This type of study can't definitively say that certain foods cause weight changes; rather it points out correlations. Researchers stress that you can't lose weight simply by avoiding French fries. Moreover, friends of the potato point out that the tuber remains a good source of vitamin C, several B vitamins, and minerals including iron, potassium, phosphorus and magnesium.
Yet it is helpful to have the type of scorecard produced by the study indicating which foods are more likely to encourage overeating and which ones are associated with weight loss. Scanning that scorecard yields some surprises — for instance, that munching on an extra daily serving of nuts helped prevent about a half a pound of weight gain. Eating an extra serving of yogurt kept off about a pound of weight gain. The researchers aren't sure why but speculate it might have something to do with yogurt's bacteria, or with the fact that big yogurt eaters tend to eat healthfully and exercise anyway.
The bottom line seems to be that weight gain still boils down to how many calories you take in and how many you burn, but that eating some foods makes it easier to go off the rails and distort that crucial equation. Anyone who has polished off a whole bag of potato chips in one sitting knows what the scientists are talking about.
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