Mediterranean Diet. There isn't one specific Mediterranean diet. The approach is an alternative to the typical overprocessed, fat- and sugar-laden American diet, and emphasizes fish, vegetables, and whole grains drizzled with olive oil. It's nutritionally sound and appropriate for all ages. "Some people say, 'I can't follow this diet because I don't like the foods,'" Fung says. "But actually, you can build a Mediterranean diet with very typical foods. Even someone like me, who doesn't like olives or grape leaves—I can still do it." That's because the approach doesn't ban entire food groups, which makes long-term compliance easier for all family members.
Vegetarian Diet. Most vegetarians choose a lacto-ovo approach, eliminating meat, fish, and poultry, while still eating eggs and dairy. The approach is more family-friendly than is super-restrictive veganism, which bans all animal products, including dairy. When done right, vegetarianism is nutritionally sound and can be tailored to all calorie levels. (A French-fries-and-doughnut diet technically counts as vegetarian.) What's more, research suggests going vegetarian helps keep the weight off and prevents chronic diseases, such as diabetes. Children will have an easier time adjusting to a vegetarian diet if they adopt it young, says Katz, since the older they get, the more difficult they'll find the sudden restrictions to be. Though doable, it does take planning to build a menu that meets the nutrition needs of vegetarians of all age; the American Dietetic Association says key nutrients to focus on are protein, omega-3 fatty acids, iron, zinc, iodine, calcium and vitamins D and B-12. Vegetarians sometimes develop B-12 deficiencies, since the vitamin is most plentiful in seafood and beef, but it's possible to get enough from milk, yogurt, fortified cereals, and supplements.
Volumetrics. Some foods are less energy dense than others—that is, they have fewer calories per gram. Volumetrics teaches you to fill your plate with more of those, so you take in fewer calories without actually eating less food. The approach is heavy on fruits, veggies, and whole grains, and light on saturated fat and salt. It's safe, balanced, and easy to follow. Plus, you're allowed to eat out and splurge on occasion—and flexibility and variety are vital components of a family-friendly diet.