U.S. News and World Report's annual list just came out. Here are the top diets, plus a few stinkers unlikely to be healthy and sustainable.

By Cynthia Sass, MPH, RD
January 04, 2021
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U.S. News and World Report just released their Best Diets of 2021 list—generated annually by a panel of experts who evaluate modern and popular diets based on safety, how easy the plan is to follow, nutritional value, and how effective the diet is for weight loss. The best diets of 2021 also have to be effective at preventing diabetes and heart disease, and evidence of these outcomes, via published studies, weighed heavily in their rankings. Here are the five top diets, and my thoughts on each as a registered dietitian.

1. Mediterranean diet

I fully expected the Mediterranean diet to rate at the top again this year. The eating pattern has long been considered the gold standard for nutrition, disease prevention, wellness, and longevity. The Mediterranean diet is rich in vegetables, fruits, fish, nuts, pulses (beans, lentils, peas, chickpeas), and olive oil. It severely limits processed foods and sugar, as well as red meat, and naturally provides a wide range of anti-inflammatory antioxidants.

Numerous studies have shown that people who live in countries that border the Mediterranean Sea, and continue to eat the region’s traditional diet, live longer and have lower rates of chronic diseases, including heart disease, which remains the top killer of both men and women in the US. It has also been shown to support better sleep quality and guard against depression.

The Mediterranean diet is nutritionally balanced and provides a diverse array of satiating foods and flavors. However, it is an eating style, not a rules-oriented diet. As such, there are no guidelines for specific portions, calorie targets, or meal configurations. That said, you may lose weight simply by shifting your intake away from processed foods toward more fiber and nutrient-rich produce and whole foods.

2. (tie) DASH diet

Tied for number two is the DASH diet. DASH is an acronym for Dietary Approaches to Stop Hypertension, but it’s not only for people with high blood pressure. DASH is promoted by the National Heart, Lung, and Blood Institute, which is part of the National Institutes of Health (NIH).

This plan borrows elements of the Mediterranean diet, but it's a very specific eating pattern that’s been highly researched. In addition to being effective for reducing blood pressure, DASH has been shown in studies to promote weight loss, protect heart health, as well as lower the risk of type 2 diabetes, metabolic syndrome, and certain cancers. DASH recommends specific portions from various food groups, depending on one’s daily calorie needs.

DASH has actually been in existence for over two decades, and I have counseled many people about how to follow the plan. It’s fairly straightforward, and while and rate of weight loss with DASH can be slow, it’s sustainable long-term. My one issue is the lack of obvious alternatives to animal protein for those who are looking for a plant-based plan. It’s also a bit lower in healthful fats than I typically recommend.

2. (tie) Flexitarian diet

A flexitarian diet is primarily vegetarian with the occasional inclusion of meat or fish. Numerous studies have shown that the shift towards a mostly plant-based diet is tied to lower body weight and a reduced incidence of chronic diseases, including improved markers of metabolic health, blood pressure, and reduced risk of type 2 diabetes.

There is no one way to follow a Flexitarian diet, as far as the number of times per week animal products are consumed or the overall makeup of a day’s worth of meals in regards to servings of produce, whole grains, etc. The best way to follow this plan is to maximize your intake of whole plant foods and minimize highly processed foods, even if they are fully plant-based. Opt for dishes like a grain bowl made with leafy greens, veggies, quinoa, lentils, and tahini over a vegan cheeseburger with fries.

4. WW (formerly Weight Watchers) diet

WW ranks highly because it is well researched, longstanding, and not extreme in its approach. The newer version is also set up in a different way, with options for how to follow the plan based on members’ food and lifestyle preferences. WW members can also access personal coaches, an app, trackers, recipes, fitness info, and a 24/7 chat service. There is even an option for those who want to build healthy habits without focusing on weight loss.

The WW plan is customizable, and unlike old school commercial weight loss programs, no food purchases are required. One potential downside can be the cost, which varies based on the chosen plan, but can be as much as $54.95/month plus a $20 starter fee.

In my experience WW can work well for people who thrive when they're part of community, like to use digital tools, and prefer an eating plan that provides structure but allows for flexible choices.

5. (tie) Mayo Clinic diet

The Mayo Clinic diet is from the highly esteemed American academic medical center and is focused on integrated health care, education, and research.

The diet, which is supported by a book and website, are based on research-backed, tried and true healthy habits. There is a strong emphasis on fitting in 30 minutes of physical activity most days of the week, eating more whole foods, including veggies, fruit, whole grains, and healthy fats, and limiting sugar to what's naturally found in fruit.

The plan includes two phases, "Lose it!" and "Live it!" The first emphasizes 15 key habits to focus on and which ones to eliminate, without counting calories. After two weeks, the next phase involves identifying how many calories you should aim for to either lose or maintain weight, and how to consume your calories in a healthful, balanced way. No foods are completely off limits though, as the diet stresses a long-term, maintainable lifestyle approach.

A digital version of the program is offered for $5 per month, which promises to help you “eat well, get moving, track healthy habits, and stay motivated.” It includes personalized meal plans, recipes, portion control guides, motivational tips, food and fitness journals, habit trackers, walking and running guides, and fitness tips for all levels. The site also features success stories that include both men and women who have shed pounds and improved their health by following the plan

5. (tie) MIND diet

The MIND diet combines aspects of the Mediterranean diet and the DASH diet to create an eating pattern designed to focus on brain health—including the prevention of dementia and age-related cognitive decline. But the MIND diet can be followed by anyone for weight loss and overall wellness.

MIND specifically stands for the Mediterranean-DASH Intervention for Neurodegenerative Delay. Because both the Mediterranean diet and the DASH diet have such strong research to support their healthfulness, MIND highlights aspects of the two that are particularly protective to the brain.

Rather than a set meal plan, MIND’s primary directive is to eat more of 10 brain-defending foods, such as green, leafy vegetables, nuts, berries, beans, olive oil, whole grains, fish, poultry, and wine (no more than one glass daily, preferably red). The plan also lays out five foods to avoid, which have been shown to hinder brain health: butter and margarine, cheese, red meat, fried food, and pastries and sweets .

Since MIND is newer than both the Mediterranean diet and DASH, there are fewer studies on its outcomes. However, the published research is impressive. In one study of nearly a thousand older adults, those who followed the MIND diet most closely had a 53% lower risk of developing Alzheimer’s disease compared to those who deviated from it most.

One downside of the diet is understanding how to transform the guidelines into concrete meal plans and recipes. Books and online resources can help, but customizing the plan to your eating preferences and weight loss goals may require some expert guidance.

Diets that ranked poorly

The diets that rated the lowest included the Dukan diet in last place and the Keto diet as second to last. While these plans may result in initial weight loss, they lose points for their restrictiveness, potential nutrient deficiencies, and lack of research on long-term effectiveness and health outcomes. These are important points to take into account if you’re considering adopting a new diet.

In my experience counseling many people over the years, I have come to a few solid conclusions. First, if a diet helps you lose weight but compromises your physical or emotional well-being, it’s not a healthy, sustainable option. Second, keeping weight off is about developing habits you can stick with long-term. If you can’t realistically see yourself following a given plan six months or a year down the road, it’s probably not the right approach for you.

Finally, weight management and health aren’t about being perfect or strict. The ultimate formula is really about balance. That concept is a not as sexy as a trendy new diet—but it’s the ultimate win-win for weight loss and wellness.

Cynthia Sass, MPH, RD, is Health's contributing nutrition editor, a New York Times best-selling author, and a private practice performance nutritionist who has consulted for five professional sports teams. 

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