A long-term study done by researchers at the US’s Harvard University tracking weight gain among Americans has found that yogurt is a star player when it comes to losing weight. “An increased intake of dairy products, whether low-fat (milk) or full-fat (milk and cheese), had a neutral effect on weight,” the New York Times reports. “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. That yogurt, among all foods, was most strongly linked to weight loss was the study’s most surprising dietary finding, the researchers say. Participants who ate more yogurt lost an average of 0.82 pounds every four years.”

“Yogurt contains healthful bacteria that in animal studies increase production of intestinal hormones that enhance satiety and decrease hunger,” Dr. Frank B. Hu, a nutrition expert at the Harvard School of Public Health and a co-author of the new analysis, says. “The bacteria may also raise the body’s metabolic rate, making weight control easier.”

The new research, by five nutrition and public health experts at Harvard University, is a detailed long-term analysis of the factors that influence weight gain, involving 120,877 well-educated men and women who were healthy and not obese at the start of the study. The study participants – nurses, doctors, dentists and veterinarians in the Nurses’ Health Study, Nurses’ Health Study II and the Health Professionals Follow-up Study – were followed for 12 to 20 years. Every two years, they completed very detailed questionnaires about their eating and other habits and current weight. Results were published in June in The New England Journal of Medicine.

The analysis examined how an array of factors influenced weight gain or loss during each four-year period of the study. The average participant gained 3.35 pounds every four years, for a total weight gain of 16.8 pounds in 20 years.

Foods that contributed to the greatest weight gain were not surprising. Chips 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 crisps (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 per cent fruit juice (0.31 pound) and butter (0.3 pound).

Also not too surprising were most of the foods that resulted in weight loss or no gain when consumed in greater amounts during the study: fruits, vegetables and whole grains. Compared with those who gained the most weight, participants in the Nurses’ Health Study who lost weight consumed 3.1 more servings of vegetables each day.