What Makes a Healthy Diet?

A healthy diet doesn't require a lot of money, newfangled appliances or subsisting on any kind of scheme that sounds like a gimmick. Because it's true what they say about what seems too good to be true: Eating well means listening to that little voice inside that knows what healthy foods generally look like -- fresh and recognizable in nature -- and what they don't: prepackaged and processed.

That sensibility may not fit so well with our on-demand culture, where we want results now -- be it dinner or weight loss. If you want a program that works in the long run, you'll need a lifestyle you can live with and like. That means a diet that's nutritious and delicious, and that will take a bit of planning and commitment from you.

[See: 6 Ways to Train Your Brain for Healthy Eating.]

While staying lean is a big part of good health, weight lost doesn't always equal health gained. That new diet that took inches off your waistline could be harming your health if it locks out or severely restricts entire food groups, relies on supplements with little scientific backing or clamps down on calories to an extreme.

"Keeping up with the latest diet craze is becoming a full-time job," says Lisa Jones, a registered dietitian in Philadelphia. "It's overwhelming." She notes that research can sometimes seem confusing. For example, one day you might read about a new study that says eating eggs is healthy. The next day, you learn about another that suggests consuming eggs could be bad for your heart health.

With our Best Diets 2020 rankings, you can check the nutritional completeness and safety of 35 popular diets, from Atkins to the Fertility Diet to WW (Weight Watchers), in a detailed profile crafted for each one. (The profiles also cover scientific evidence, typical meals and much more.) And U.S. News' Best Diets for Healthy Eating rankings give each diet a "healthiness" score from 5 (best) to 1 (worst) for safety and nutrition, with safety getting double weight; while you can modify a diet to some degree to adjust for nutritional imbalances or deficiencies, mere tweaking won't make an unsafe diet safe.

[See: 10 Lessons From Extreme Dieting.]

Behind these scores are ratings by a panel of diet and nutrition experts assembled by U.S. News. They assessed the diets across seven categories, including the safety and nutritional completeness categories, for a series of nine different rankings lists. The Best Diets for Healthy Eating rankings overlap significantly with Best Diets Overall. Both give especially high marks to the DASH, MIND, TLC, Mediterranean, Mayo Clinic and Volumetrics diets.

"The ones that get high scores in safety and in nutritional value -- they're very similar to each other," says Andrea Giancoli, a registered dietitian who serves on the U.S. News expert panel. The recurring theme across the diets that excelled in healthiness is adequate calories supplied by a heavy load of vegetables, fruits and whole grains; a modest amount of lean protein, nonfat dairy and healthy fats; and an occasional treat. Plants are the foundation, and the menu is always built around minimally processed meals made from scratch.

Because plant-based eating patterns are so healthful and growing in popularity, U.S. News also offers a Best Plant-Based Diets category. And given the rise of food intolerances and sensitivities, we've included profiles of diets that are said to ease digestive distress -- the gluten-free and low FODMAP diets. These are not ranked, however, as they are not intended for general dietary needs.

[See: 7 Reasons to Choose a Plant-Based Diet. ]

Eight plans on the Healthy Eating list received healthiness scores below 3; these included the Paleo, Raw Food, Fast, Dukan, Atkins and Whole30 diets. They're simply too restrictive, say our experts, who call their nutritional qualities into question. The meat-heavy Paleo diet bans grains and dairy, so getting adequate calcium and vitamin D isn't easy. Atkins, by severely curbing carbs, blows past recommended caps for total and saturated fat. Depending on your personal approach to the Raw Food Diet, you may shortchange yourself on calcium, vitamin B12 and vitamin D; its restrictive cooking rules also could put you at risk for eating raw or undercooked ingredients.

If you have reservations about a diet's nutritional content or safety, listen to your body. Fatigue, sleeplessness, dizziness, aches -- they're all red flags.

It's important to keep in mind that a healthy diet isn't only or all about losing weight, says Denice Taylor, a registered dietitian at Texas Health Arlington Memorial Hospital in Arlington, Texas. "A healthy diet is one that improves health and helps fight disease," Taylor says. "We know that there is not one diet that's right for everyone, so it's important to follow an eating plan that's packed with tasty, healthy foods that keep your unique lifestyle in mind."