Potato chips were associated with the heftiest gain in weight in a Harvard School of Public Health study published Thursday that explored the effects of diet and lifestyle factors on weight gain.

The study, published in the New England Journal of Medicine, found that potatoes, sugar-sweetened beverages, and some meats were the most significant factors associated with weight gain among research participants.

Led by Associate Professor Dariush Mozaffarian, the study followed two groups of female nurses and one of male health professionals, evaluating them once every four years over a period of 12 to 20 years.

While potatoes were linked with the greatest gain in weight, other foods commonly associated with weight gain, such as desserts and alcohol, were found to have had a lesser effect. Meanwhile, increased consumption of vegetables, whole grains, fruits, nuts, and yogurt was associated with weight loss.

Various lifestyle habits also accounted for weight change, the study found. On average, participants who slept more than eight or less than six hours per night gained more weight than those who slept between six and eight hours per night. Also, increased television viewing and cessation of smoking were both associated with weight gain, while continuing to smoke was associated with weight loss.

Walter C. Willett, a co-author of the study and the chair of the Department of Nutrition at the School of Public Health, said that what distinguished this study was not what factors it analyzed but how it analyzed those factors.

“Most of the factors we looked at actually had been studied before. We’ve seen each of those aspects, like sugary beverages related to more weight gain, one at a time,” he said. “But what we did here was put all these pieces together.”

Average weight gain among subjects was 0.8 lb per year. Yet, taken over a long time period, even this gradual weight gain has long-lasting implications for weight-associated health issues, the study said.

But there is no silver bullet to avoid those issues, Willett said.

“There is not a single food that will keep you slim,” Willett said, “but there are many that will make it a little more or less likely that you will be able to control your weight in long run.”

—Staff writer Leanna B. Ehrlich can be reached at lehrlich@college.harvard.edu.