People who ate an extra serving of vegetables per day gained 0.22 fewer pounds over a four year period than people who did not. More yogurt meant a 0.82 pound dip, more fruit equaled 0.46 fewer pounds and more nuts meant 0.57 fewer pounds.

Researchers said people who ate more low-fat, high-fiber foods may have effectively "displaced other, more highly processed foods in the diet," which could explain why they gained less than their counterparts over time.

"These findings underscore the importance of making wise food choices in preventing weight gain and obesity," said senior author Frank Hu, professor of nutrition and epidemiology at Harvard.

"The idea that there are no 'good' or 'bad' foods is a myth that needs to be debunked."

Some lifestyle changes such as less exercise and more television watching were also linked to weight gain.

A good night's rest, but not too much rest, appeared beneficial too. People who slept between six and eight hours per night gained less weight over time than people who slept fewer than six hours or more than eight.

"Small dietary and other lifestyle changes can together make a big difference - for bad or good," said lead author Dariush Mozaffarian of the Harvard School of Public Health.

"This makes it easy to gain weight unintentionally, but also demonstrates the tremendous opportunity for prevention. A handful of the right lifestyle changes will go a long way."

Food that can make you gain or lose weight Click on thumbnail to view. Story continues after photos. (Photos: ST, TNP, Reuters, AFP)