Chuck the chips. Forget the fries. They’re the foods most responsible for Americans gradually getting fatter and fatter over the past 20 years. In fact, potatoes of all persuasions – baked, boiled and mashed in addition to chips and French fries – were linked to weight gain among people who ought to know better – the 120,877 doctors, nurses and other health professionals whose eating habits, lifestyle and weight were tracked for 20 years in three big government-sponsored studies.
Every four years, researchers from Harvard Medical School and Brigham and Women’s Hospital in Boston checked up on the participants’ eating habits, lifestyle and weight. Overall, the average gain among study participants during the study was 17 pounds. Here are some surprising insights from the research, as well as the five best and five worst foods for weight loss or maintenance.
The five most fattening foods
While potato chips and other potato dishes are the two most fattening foods according to the study, they aren’t solely responsible for our widening waistlines. Sugar-sweetened beverages, red meat and processed red meat rounded out the list of the top five foods most likely to pack on pounds. Each one of them was associated with one pound of weight gain every four years. But French fries led to a gain of more than three pounds every four years while each extra serving of chips per day led to a gain of 1.69 pounds every four years. Surprisingly, sweets and desserts didn’t make the cut, although they were responsible for a gain of .41 pounds for each four year period.
Why are potatoes so fattening
Our problem with potatoes may be that we tend to eat big portions. Another possibility: potatoes can cause spikes in blood sugar and insulin that can lead to overeating at the next meal, by revving up appetite. Other starchy refined foods, such as white bread, desserts and low-fiber breakfast cereal, may have a similar effect. And potatoes are often served fried, which increases the calories.
Surprising lessons in weight control
Conventional wisdom holds that all we need to do to slim down is eat less and move more. But the study authors concluded that we need to rethink that notion. Their findings also indicate that another old saw, “all things in moderation,” may not work out so well either. Instead, the study results suggest that if we want to avoid gaining weight or lose extra pounds we’ve already put on, we should be focusing on the quality of the foods in our diets and habitually eating more of the healthy ones.
The five best foods for weight loss
The study found that participants who lost weight or didn’t gain any over the 20 years also ate more vegetables, fruits, whole grains, yogurt and nuts, including peanut butter, which is getting considerable respect these days as a healthy food. Yogurt’s role in weight control was unexpected. It topped the list of foods associated with weight loss among the study participants. Those who ate the most yogurt lost nearly a pound every four years. Another good bet: lots of vegetables. Women in the Nurses’ Health Study who lost weight over the 20 years ate 3.1 more servings of vegetables daily (compared to those who gained weight). The study also found that most dairy products – including full-fat milk and cheese – had a neutral effect on weight.
How much impact does working out have? As far as exercise is concerned, the study found that participants who increased their exercise time the most gained 1.76 pounds less at each of the study’s four year intervals than those who made no change in their exercise patterns.
Bad Habits that Pile on Pounds
In addition to identifying the foods that most affect weight, the study also assessed the impact of several lifestyle factors:
- Sleep: Too little (less than six hours) or too much (more than eight hours) have been associated with weight gain in other studies and showed up in this new one, too.
- TV Time: No surprise, the more time participants spent watching television, the more weight they gained over the 20 years. TV watching fosters snacking, perhaps because of all the the food commercials we see, the researchers suggested.
- Smoking: The study showed that participants who continued smoking for the duration, lost more than a half pound during each four-year period. The authors theorized that the weight loss might have been due to undiagnosed illness among those who continued to smoke because no weight loss or gain was seen among participants who began to smoke during the study.
- Alcohol: A daily glass of wine didn’t lead to weight gain but increased intake of other types of alcohol did.