6. GO FISH A nutrient-rich protein fish is generally low in calories and high in essential fatty acids, which protect the membranes inside blood vessel walls. "The omega-3 fatty acids in fish also help lower cholesterol, improve joint function in people with arthritis, and can improve brain function, much as leafy greens and berries do," says Paula Bickford, Ph.D., a professor at the Center for Aging and Brain Repair at the University of South Florida College of Medicine in Tampa. Eat wild, not farm-raised fish, suggests Light: "Farm-raised fish are fed refined grain products—without a diet of phytoplankton, farm-raised fish have much less omega-3 fatty acids than wild fish." But limit your intake of large ocean fish like tuna or swordfish because of their higher mercury content. (The bigger the fish, the longer it's had to accumulate mercury from industrial pollution.) Opt for younger, smaller fish, such as Alaskan wild salmon, tilapia, mackerel, or mahi mahi. Alternatively, choose B12-fortified vegan foods like yeast extracts, veggie burgers, soy and nut milks, and breakfast cereals.
7. HIT YOUR TARGET WEIGHT You don't have to eat like a calorie-restricted rat, but it pays to establish limits and maintain a healthy body weight. "Excess weight is a tremendous risk factor for chronic conditions such as cancer, diabetes, heart disease, and arthritis," says Clark. Calculate your best weight this way, she adds: Women optimally weigh 100 pounds at 5 feet, and 5 pounds more for each additional inch; men weigh 106 pounds at 5 feet, plus 6 pounds for each additional inch. If you are sedentary, you need to eat only 14 calories per pound of your body weight to maintain it; if very active, you need 16 calories per pound. Cut 500 calories per day to lose about a pound a week.