We gain an average 20 pounds between the ages of 25 and 55. Consumer Reports surveyed 21,000 readers to find the secrets to keeping the weight off.

"People who've always been thin typically aren't sitting around eating potato chips." said Consumer Reports Jamie Kopf Hirsh. "Only three percent of the thin people we surveyed said they ate whatever they pleased and never exercised."

As for the successful dieters, most lost the weight without the help of a diet program, diet pills, or a medical treatment.

Their strategies were similar to those of the naturally thin.

Portion control is a given.

Other winning strategies:

--Eating fruits and lots of vegetables

--Opting for whole-wheat breads and other whole grains rather than white flour

--and limiting fat

That plus exercise. While vigorous exercise is particularly effective, Consumer Reports' survey showed any physical activity is helpful.

Consumer Reports' survey also found those who weigh less eat out less.