NEJM: Yogurt good, potatoes bad for long-term healthy weight

New study indicates that types of foods consumed, not just calories taken in, may play a role in long-term weight gain.

The conventional weight-loss strategy, “eat less and exercise more” is not an adequate plan for preventing long-term weight gain, according to a new study in the New England Journal of Medicine.

Harvard researchers on the study, led by Dariush Mozaffarian, M.D., Dr.P.H, indicated that the quality of the food one eats, not necessarily the quantity, is a better indicator of weight gain over time. With the recent study, “Changes in Diet and Lifestyle and Long-Term Weight Gain in Women and Men,” the researchers were able to connect particular foods to weight-gain predictions.

The research included 120,877 U.S. men and women, free of chronic disease, including baseline obesity. Follow-up periods on the study included 1986-2006; 1991-2003; and 1986-2006, for three separate cohorts. Relationships between lifestyle factors and weight change were evaluated at 4-year intervals, with various adjustments made for age, baseline BMI, and lifestyle factors. Researchers found that cohort-specific results, as well as sex-specific results, were similar.

"For diet, conventional wisdom often recommends 'everything in moderation,' with a focus only on total calories consumed," said Dr. Mozaffarian, an associate professor of medicine and epidemiology at Harvard Medical School and Brigham and Women's Hospital, reported Time Healthland. "Our results demonstrate that the quality of the diet — the types of food and beverages that one consumes — is strongly linked to weight gain."

Overall, the participants gained 3.35 lbs., or 2.4% of their body weight, in each four-year interval. Over the 20 years of follow up, that amounted to almost 17 additional pounds on the scale. Additionally, the data revealed a strong weight-gain connection with certain foods, such as various forms of potatoes, including chips; sugar-sweetened beverages; unprocessed red meats; and processed meats. These types of foods in participants’ diets and weight gain were inversely connected to the amount of vegetables, whole grains, fruits, nuts and yogurt consumed, i.e. those who ate more of the latter group gained less weight over time. Yogurt, in fact, prevented 0.82 lbs. of weight gain over time, a finding that Mozaffarian indicated was unexpected and in need of additional study.

Some lifestyle factors were independently associated with weight changes, including physical activity, alcohol consumption, smoking, sleep activity and watching TV. Those who exercised more tended to gain less, while those who slept less than six hours and more than eight hours tended to gain more. Data also indicated that each additional alcoholic beverage per day added 0.41 lbs. every four years. For new quitters and former smokers, weight gain was new 5.17 lbs. and 0.14 lbs, respectively. And, television watching tended to contribute more to weight gain than other sedentary activities, said Mozaffarian, because people tend to snack both while watching and afterwards, due, he said, to food commercials. "Turning off the TV is therefore very important — in particular, to improve diet. If TV must be watched, then it should be done without any eating and without any food or beverage advertising."

"Small dietary and other lifestyle changes can together make a big difference — for bad or good," said Mozaffarian. "That makes it very easy to gradually gain weight unintentionally, but also means that a little bit of attention to a handful of dietary and other lifestyle changes can prevent this."

The full study appears in the New England Journal of Medicine online today.

Image: Wikimedia Commons

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