U.S. News & World Report, in collaboration with a panel of health experts, evaluated and ranked 41 diets. To be top-rated, a diet had to "be safe, relatively easy to follow, nutritious and effective for weight loss." It also had to be proven to help prevent heart disease and diabetes.
Here's a closer look at the highest-ranking diets overall.
1. Mediterranean diet
The Mediterranean diet got the top ranking in U.S. News' list. The heart-healthy diet is rich in fruits, vegetables, fish and whole grains, along with healthy fats like olive oil, nuts and avocados.
Research has shown the Mediterranean diet reduces the risk of heart disease and may have numerous other health benefits, including reduction of LDL, or "bad," cholesterol, as well as a decreased risk of Alzheimer's disease, Parkinson's disease and cancer. In fact, one recent study published in British Journal of Nutrition found adhering to the Mediterranean diet was associated with a 25 percent lower chance of death from any cause.
2. DASH diet
The DASH (Dietary Approaches to Stop Hypertension) diet was designed to help manage blood pressure, but experts say it has many overall health benefits, helping it nab the number 2 spot on the best overall diets list.
The diet emphasizes healthy food sources, including fruits, vegetables, whole grains, skinless poultry and fish, and nuts and legumes. It also limits red meat, salt, and sweets.
In addition to lowering blood pressure, research suggests the DASH diet may help reduce the risk of diabetes and may also help fight depression.
3. Flexitarian diet
Flexitarian is a marriage of the words "flexible" and "vegetarian." The term was coined by registered dietitian Dawn Jackson Blatner in her book "The Flexitarian Diet: The Mostly Vegetarian Way to Lose Weight, Be Healthier, Prevent Disease and Add Years to Your Life." U.S. News ranked it high on the list for being nutritionally complete, easy to follow, and providing long-term weight loss as well as heart health benefits.
In the book, Blatner says you don't have to cut out meat entirely to reap the health benefits of a vegetarian diet. Eating a diet that's mostly vegetarian while also allowing for an occasional burger or steak to satisfy a craving can help with weight management and improve overall health, Blatner says.
4. (tie) MIND Diet
The MIND Diet combines many elements of two other popular nutrition plans which have been proven to benefit heart health: the Mediterranean diet and the DASH diet. (MIND stands for Mediterranean-DASH Intervention for Neurodegenerative Delay.)
Designed by researchers from the Rush University Medical Center in Chicago, the aptly named MIND diet was developed specifically for brain health. In fact, one study found the diet may reduce the risk of developing Alzheimer's disease by as much as 53 percent. Even those who didn't stick to the diet perfectly but followed it "moderately well" reduced their risk of Alzheimer's by about a third, the researchers found.
4. (tie) Weight Watchers diet
The Weight Watchers diet tied for fourth place with the MIND diet. Although designed to help people lose weight, experts say its focus on healthier living makes it a smart overall diet to follow.
The WW Freestyle program was launched in 2017 and builds off the company's signature SmartPoints system, which assigns every food and beverage a point value, based on its nutrition. The new program expands dietary options. The plan also involves in-person meetings or online chats designed to support those in the program and keep them accountable.
Low ranking diets
A number of popular diets, including the keto diet, Dukan diet, and the Whole30 diet received some of the lowest rankings on U.S. News' list.
Lack of scientific evidence for health benefits and severe restriction of foods – including certain healthy foods – were listed as reasons for low scores.