While many struggle with their weight and count calories, everyone has slim friends who never seem to gain weight. What kind of simple rules of thumb, principles or benchmarks do they use that lead them to take less, order less and eat less?

“Their secrets are usually very simple,” says Cornell Professor Brian Wansink, director of the Cornell Food and Brand Lab. “For instance, when we ask them what they do at summer picnics, they say things like eat only home-made foods, or taste everything and then go back for seconds on the favorites, or eat only one dessert.”

To systematically determine what slim people do, Wansink and colleagues at the Cornell Food and Brand Lab have launched the Slim by Design Registry. Announced at the annual meeting of the TOPS (Take Off Pounds Sensibly) Club, a nonprofit weight-loss support and wellness education organization, in Milwaukee last month, the registry is intended to collect these tips in a way that can help slim people stay slim and the rest of us to slim down.

The registry is modeled on the National Weight Loss Registry, which asked people to register and share their experiences if they had lost 30 pounds and kept it off for three years. It gave hundreds of thousands of people insights into how to take weight off and keep it off, Wansink says.

However, the Slim by Design Registry is only open to people who have never gained weight.

“We’re interested in members who have been a healthy weight all of their life,” says Wansink. “By knowing what they do, we can become more slim by design rather than slim by willpower.”

Upon completing a short prescreening survey at SlimByDesign.org, potential registry members are invited to complete an intake survey. The questions range from what they eat for their typical breakfast to what they do to avoid nighttime snacking; it asks about cooking secrets, philosophies on food and eating, and even about basic outlooks on life. Upon finishing the intake survey, people are sent a welcome kit and regular newsletters of tips from survey results. Abbreviated findings will be available on the Web. Twice a year, registrants will be invited to answer follow-up questions.

At the website, readers can review some lists on what slim people say they do. For example, it shows that what slim people do to feel full are eat soups and stews, hard-boiled eggs, Greek yogurt, salmon or tuna and add eggs to dishes.