The Mediterranean diet — rich in healthy fats, fish, whole grains, and produce, and low in processed foods and red meat — was named the overall best diet for 2020 by US News & World Report.

This is the third straight year the Mediterranean diet has topped the site's annual list, over competitors like keto, veganism, and commercial plans like Weight Watchers and Jenny Craig.

The diet also was also named the easiest diet to follow and was ranked highly because of its benefits for heart health and diabetes prevention.

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Every year, US News & World Report ranks the best diets for the year ahead. In 2020, for the third year in a row, the Mediterranean diet was named the overall best diet.

A panel of nutritionists and specialists in diabetes, heart health, and weight loss made the Mediterranean diet their top pick out of 35 eating plans, including trends like the keto diet and commercial options like Weight Watchers, Atkins, and Jenny Craig.

The rankings were based on seven categories in which each diet was rated on a scale from one to five. Categories were nutritional completeness, how easy the diet is to follow, the potential for long- and short-term weight loss, the safety and possible side effects, and the potential to help prevent illnesses like heart disease and diabetes.

The Mediterranean diet was named not only the overall best diet, but the easiest diet to follow, the best at preventing diabetes, and the best plant-based diet. Overall, broad eating patterns topped the list, while restrictive diets like keto remained at the bottom.

The Mediterranean diet is high in fresh fruits and vegetables and low in red meat and sugar

The concept of the Mediterranean diet comes from the countries that border the Mediterranean Sea, where people historically ate mainly produce, nuts, and healthy fats. The Harvard School of Public Health and a think tank called Oldways created a diet based on the general eating principles of these places, according to US News & World Report.

Many of these areas are part of the so-called blue zones, regions of the world where people tend to live the longest, healthiest lives.

The Mediterranean diet relies heavily on seafood, fresh produce, whole grains, nuts, and seeds. People on the plan can also enjoy wine in moderation.

These foods are rich in vitamins as well as important nutrients like fiber and polyphenols, plant-based compounds that help protect against disease. As such, the diet has been found to help reduce the risk of diabetes and may protect against certain types of cancers as well as cognitive decline.

It can even help with weight loss by cutting out high-calorie processed foods and refined sugars in exchange for more nutrient-dense alternatives like veggies and fish.

Since the diet focuses on heart-healthy fats like olive oil, avocado, and salmon, it also could lower bad cholesterol, a major cause of heart disease, according to the Mayo Clinic.

The University of Iowa's Cardiovascular Risk Service said that the diet "discourages saturated fats and hydrogenated oils (trans fats), both of which contribute to heart disease."

The Mediterranean diet doesn't restrict calories or include rigid meal-planning, which helps make it easier to follow and be among the safest diets in terms of unwanted side effects. However, this may also be a drawback for people looking for a more structured eating style or trying to lose weight quickly.

The Mediterranean diet doesn't restrict calories or include rigid meal-planning. casanisaphoto/ iStock

Restrictive diets like keto, Whole30, and the raw-food diet ranked low on the list

Many diets were ranked low overall by US News & World Report in part because they're difficult to sustain in the long term. These include the high-fat, low-carb keto diet, which was ranked highly for short-term weight loss but little else.

The raw-food diet, which prohibits any foods heated above a certain temperature, was also low on the list, since it cuts out many perfectly healthy foods.

And the monthlong, highly restrictive Whole30 diet, which cuts out all grains, sugars, breads, desserts, alcohol, dairy, legumes, and processed foods, is not only difficult to follow, but not backed by science, and experts continue to be skeptical of it.

But other sustainable eating habits, like the flexitarian diet, continue to be highly ranked by experts

The other standout winner this year was the flexitarian diet.

Though the name sounds like it's designed for bodybuilders, it actually refers to a flexible eating style: sticking to mostly plant-based foods, while allowing high-quality animal products in moderation.

The flexitarian diet was second only to the Mediterranean diet in four categories, including best overall, and it was highly ranked for weight loss and heart health.

This suggests that fad diets will continue to be just that — a passing trend — while confirming what the experts have known for years: that the best diet is the one you can stick to.