(CNN) If you're a fan of the Mediterranean diet, get ready to do a victory dance. For the first time, the Mediterranean diet has won the gold as 2019's best overall diet in rankings announced Wednesday by US News and World Report.

The analysis of 41 eating plans also gave the Mediterranean diet the top spot in several subcategories: best diet for healthy eating, best plant-based diet, best diet for diabetes and easiest diet to follow.

The diet features simple, plant-based cooking, with the majority of each meal focused on fruits and vegetables, whole grains, beans and seeds, with a few nuts and a heavy emphasis on extra virgin olive oil. Say goodbye to refined sugar and flour except on rare occasions. Fats other than olive oil, such as butter, are consumed rarely, if at all.

Meat can make a rare appearance, usually only to flavor a dish. Instead, meals may include eggs, dairy and poultry, but in much smaller portions than in the traditional Western diet. Fish, however, are a staple.

"It's more than a diet, it's a lifestyle," said Atlanta registered dietitian Rahaf Al Bochi, who teaches the Mediterranean diet to her clients. "It also encourages eating with friends and family, socializing over meals, mindfully eating your favorite foods, as well as mindful movement and exercise for a complete healthy lifestyle."

What is a 'best diet?'

To judge the diets, a panel of experts in heart disease and diabetes, nutrition, diet, food psychology and obesity reviewed research about the diets from medical journals, government reports and other resources.

Angela Haupt, assistant managing editor of health for US News and World Report, said the experts then ranked the diets in seven categories: "how easy it is to follow, its nutritional completeness, its ability to produce short-term and long-term weight loss, its safety and its potential for preventing and managing diabetes and heart disease."

In 2018, the top spot for best overall diet was a tie between the Mediterranean diet and the DASH diet, which stands for dietary approaches to stop hypertension, or high blood pressure. This year, DASH came in second, with third place going to the flexitarian diet, a plant-based diet that allows meat on rare occasions. Fourth place was a tie between the brain-focused MIND diet and Weight Watchers.

What do all of these diets have in common? They require the use of minimally processed foods and focus on fruits, vegetables, beans, lentils, whole grains, nuts and seeds, said internist Dr. Sharon Bergquist, who founded the lifestyle medicine and wellness programs at Atlanta's Emory University.

"These minimally processed plant-based foods affect our health in a very deep way," explained Bergquist, who was not on the US News and World Report panel of experts.

"They reduce inflammation, reduce oxidative stress, balance our gut bacteria, and they're getting at the root cause of disease," she added. "It's the same consistent theme that helps with overall health."

CNN contributor and registered dietitian Lisa Drayer says the highest-ranked diets have another important commonality: They allow for the occasional indulgence.

"Whether it's a glass of red wine on the Mediterranean diet or a piece of cake on Weight Watchers, it allows people to plan for an indulgence that would otherwise be forbidden," Drayer said. "So much about weight loss is mental, and being able to incorporate all foods, including a treat, is really important for any healthy eating plan."

The lowest-ranked overall diets were the Dukan diet, the Body Reset diet, the Whole30 diet and the popular keto diet, which all focus on high-protein or high-fat foods with minimal carbohydrates.

"Those are diets that have few substantiated claims, are extremely restrictive, harder to follow, and they eliminate entire food groups, which is really not something that's substantiated by science," Bergquist said.

Best overall diet for weight loss

For this category, the panel of experts looked at a diet's short-term and long-term weight loss success, weighing both equally. The popular Weight Watchers diet came out on top.

"Weight Watchers uses a point-based system that assigns very low or zero points to fruits and vegetables," Bergquist said, adding that it recently began assigning no points for plant-based sources of protein like beans, lentils and tofu.

Weight Watchers, which also won first place in the best commercial diet category, has an important component needed in any successful diet: support. In addition to in-person meetings and optional one-on-one consultants, the plan offers an online community.

"We find that people really want to talk about their diets," Haupt said. "That's just something that helps people stick with them. And Weight Watchers has great support built into the program, and that really seems to resonate with people."

Second place for overall diet for weight loss went to Volumetrics, a diet that focuses on using low-calorie, high-density foods such as broth-based soup and nonstarchy fruits and vegetables to reduce hunger.

"It's all about energy density," Drayer said. "It explains why a low-calorie salad or a soup eaten before a meal will help you eat fewer calories for the entire meal, compared to if you skipped the salad or the soup."

Third place was a three-way tie between the flexitarian diet, the vegan diet and Jenny Craig, which also came in second for the best commercial diet.

Best diet for quick weight loss

Haupt stresses that the quick weight loss category is for the person who needs to lose a few pounds for a special occasion, as the diets were evaluated for only a two-month period.

"Effectiveness as a short-term diet does not mean that it is a good idea for long-term weight loss, which is more important for your health, "she said. "In fact, one of our experts said these techniques often contradict everything we know about long-term weight management."

According to Bergquist, these diets can be deceptive because of their initial success.

"In the short term, they may show a slightly faster rate of weight loss," she said, "but in the long term, there's no evidence that these diets are any faster or better at helping people lose weight."

What's the winner in this category? The HMR diet, which is designed for those who need to improve their health quickly by losing a significant amount of weight under close medical supervision. It offers at-home and in-clinic options, and all meals and snacks are delivered for a specific period of time.

"The calorie range for the in-clinic option is pretty low, and that's why they're providing the medical supervision to make sure that people are staying healthy while they're on the program," Haupt said.

Second place was a four-way tie: Weight Watchers, a version of the Medifast meal-replacement plan called Optavia, and the Atkins and the keto diets, which both emphasize low-carb, higher-fat meals that place the body into a state called ketosis, in which it burns fat cells for energy.

Drayer is concerned with any type of diet that is too restrictive in food choices and worries about the role of ready-to-eat meals, shakes and snacks.

"They're not necessarily teaching you how to eat healthfully on your own and how to make healthy choices," she said, adding that she had seen this happen all too often in her own clients.

"They were so severely restricted, and they didn't know how to incorporate other foods back into their diets in a reasonable way," Drayer said. "So they not only regained their weight back, but they gained even more weight than where they started, which is really distressing."

Best diets for diabetes and heart health

No surprise here: The Mediterranean diet ranked first in best diet for diabetes and tied for first place in best heart-healthy diet.

"The foods in the Mediterranean diet are really high in antioxidants, vitamins, minerals and fiber, which are all key components for reducing the risk for chronic disease," said Al Bochi, who is also a spokeswoman for the Academy of Nutrition and Dietetics.

The six-way tie for best heart-healthy diet also includes the DASH diet; the MIND diet; the vegan diet; the Dr. Dean Ornish diet, which he says is the only scientifically proven program to reverse heart disease in a random clinical trial without drugs or surgery; and the TLC diet, short for therapeutic lifestyle changes.

The Ornish diet program to reverse heart disease focuses on more than an extremely restrictive diet; it also addresses exercise, stress reduction and social support.

The TLC diet was created by the National Institutes of Health's cholesterol education program and is focused on lowering the body's bad cholesterol, known as LDL. However, it can also be used for weight loss.

When it comes to diabetes, four diets tied for second place in the US News and World Report ranking: the DASH diet, the flexitarian diet, the Volumetrics diet and the Mayo Clinic diet, which says it provides personalized meal plans, weight and fitness trackers and the expertise of nearly a dozen experts.

Why rank diets?

Haupt says the goal of the US News and World Report diet rankings is to clear away clutter.

"New diet trends are a dime a dozen," she said. "We want to provide comprehensive, trustworthy information that highlights the diet standouts and those that don't perform so well in an array of different categories."

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Bergquist agrees that expert rankings provide value to the consumer who wants to lose weight safely and improve their health.

"It's a chance for experts to help the general public separate diets that are looking for their 15 minutes of fame from diets that are based on what we know about the fundamentals of healthy eating," she said. "It's really replacing controversy and confusion with consensus."