1. Protein. In May early results were reported for the multipart study called "Diogenes" (a name created by combining the words diet, obesity and genes), which is being funded by the European Community. Researchers split 205 people who'd lost weight on a fixed diet over two months into five groups, each eating a different kind of diet, to see which group did the best at keeping the weight off. The results: participants who ate more protein were least likely to regain the lost pounds. (A diet focused on low-glycemic foods, such as diabetics follow, didn't work as well.)
2. Nuts. Although they are high in calories, research suggests that nuts help keep people thin. In one study with more than 8,000 participants, at the University of Navarra in Spain, people who rarely or never ate nuts gained slightly more over two years than those who munched on them at least twice a week (the results were adjusted for risk factors for obesity). Another study, at Loma Linda University in California, found that overweight women lost weight over six months when they were given almonds to eat and otherwise ate as they chose. Nuts contain mostly unsaturated fat, especially monounsaturated fats, which raise "good" cholesterol. They tend to be filling and may push the body to burn more fat, says Dr. Leo Galland, author of "The Fat Resistance Diet" (Broadway, 2005).
3. Fruits and Vegetables. Women who consume five or more fruit and vegetable servings daily are more likely to maintain weight loss than those who eat fewer servings, according to the Centers of Disease Control. (How much is a serving? It's about a half cup of cut-up fruit, berries, or nonleafy vegetables, one full cup of leafy veggies or one medium-size whole fruit.)
4. Berries. As you enjoy your daily servings of fruit, don't forget berries. Research at Doshisha University in Japan suggests that anthocyanins, the flavonoids that give berries (and other plant foods) a red, blue or purple color, alter the activity of genes found in human fat cells. In a separate study in which mice were fed anthocyanins, researchers found they didn't gain weight, even when they were given an otherwise high-fat diet that would typically plump them up.