This study shows that conventional wisdom isn’t the best approach. What you eat makes a difference.
Dr. Frank B. Hu, a nutrition expert at the Harvard School of Public Health and a co-author of the new analysis, said: “In the past, too much emphasis has been put on single factors in the diet. But looking for a magic bullet hasn’t solved the problem of obesity.” Also untrue, Dr. Mozaffarian said, is the food industry’s claim that there’s no such thing as a bad food.
The beauty of the new study is its ability to show, based on real-life experience, how small changes in eating, exercise and other habits can result in large changes in body weight over the years. (Gary Taubes explores this in Why We Get Fat).
On average, study participants gained a pound a year, which added up to 20 pounds in 20 years. Some gained much more, about four pounds a year, while a few managed to stay the same or even lose weight.
Participants who were overweight at the study’s start tended to gain the most weight, which seriously raised their risk of obesity-related diseases, Dr. Hu said. “People who are already overweight have to be particularly careful about what they eat,” he said.
The foods that contributed to the greatest weight gain were not surprising. French fries led the list: Increased consumption of this food alone was linked to an average weight gain of 3.4 pounds in each four-year period. Other important contributors were potato chips (1.7 pounds), sugar-sweetened drinks (1 pound), red meats and processed meats (0.95 and 0.93 pound, respectively), other forms of potatoes (0.57 pound), sweets and desserts (0.41 pound), refined grains (0.39 pound), other fried foods (0.32 pound), 100-percent fruit juice (0.31 pound) and butter (0.3 pound).
…And despite conventional advice to eat less fat, weight loss was greatest among people who ate more yogurt and nuts, including peanut butter, over each four-year period.
Nuts are high in vegetable fat, and previous small studies have shown that eating peanut butter can help people lose weight and keep it off, probably because it slows the return of hunger.
That yogurt, among all foods, was most strongly linked to weight loss was the study’s most surprising dietary finding, the researchers said. Participants who ate more yogurt lost an average of 0.82 pound every four years.
Yogurt contains healthful bacteria that in animal studies increase production of intestinal hormones that enhance satiety and decrease hunger, Dr. Hu said. The bacteria may also raise the body’s metabolic rate, making weight control easier.
But, consistent with the new study’s findings, metabolism takes a hit from refined carbohydrates — sugars and starches stripped of their fiber, like white flour. When Dr. David Ludwig of Children’s Hospital Boston compared the effects of refined carbohydrates with the effects of whole grains in both animals and people, he found that metabolism, which determines how many calories are used at rest, slowed with the consumption of refined grains but stayed the same after consumption of whole grains.