The Cooper Institute

Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH


Rating the Diets: U.S. News and World Report Annual Rankings

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Wednesday, Jan 13, 2021

It’s no secret to those of us with an interest in health and fitness that 70% of American adults are overweight or obese.*

Obesity is strongly associated with a number of chronic conditions, including cardiovascular disease, type 2 diabetes, knee osteoarthritis, and some cancers. During any given year, it is estimated that 45 million Americans will be dieting. These numbers provide a rich and fertile environment for a seemingly endless number of popular diets, some of which are very questionable at best. Each year, U.S. News and World Report provides a tremendous public service by releasing their annual ratings of popular diets.

For 2021, a team of 24 nutrition experts including Registered Dietitians, physicians, and nutrition scientists rated the effectiveness of 39 different diets in the following areas: easy to follow, nutritious, safe, effective for weight loss, and protective against diabetes and heart disease. Additional details regarding these areas can be found at the end of the blog. Each of the areas was rated on a scale of 1-5 stars. There were several different categories of best diets, including best diets overall, best weight loss diets, best commercial diets, best diets for healthy eating, best heart-healthy diets, best diets for diabetes, best plant-based diets, and easiest diets to follow. Four new diets were evaluated for this years’ list; they included the Noom Diet, Autoimmune Protocol (AIP), Gut and Psychology Syndrome (GAPS), and the Modified Keto Diets.

In the best diets overall category, the Mediterranean Diet came out on top, followed closely by a tie for second place between Dietary Approaches to Stopping Hypertension (DASH) and the Flexitarian Diet. The Weight Watchers Diet finished third. At the other end of the spectrum, bottom dwellers included the Ketogenic Diet and the Dukan Diet, as well as the GAPS, Whole30, and Modified Keto Diets. In the best heart-healthy diets category, there was a 3-way tie for first place, with the Ornish Diet, Mediterranean Diet and DASH leading the pack. The Keto, AIP, Whole30, and the Dukan Diets brought up the rear in this category. Since we have previously written blogs on the Alkaline Diet and the Paleo Diet, you might be interested to know that these diets finished 29th and 31st, respectively, in the best diets overall category. In the best heart-healthy diets category, Alkaline finished a lackluster 29th.

You might be interested in some specific comments made by the expert panel regarding some of these diets:


  • A Mediterranean style eating plan is very sensible and will showcase healthy foods like whole-grain pita and hummus, salads, fresh fruits and veggies, beans, and beneficial fats found in foods such as salmon, nuts and seeds, as well as olive oil.
  • The DASH plan was lauded for its nutritional completeness and safety, as well as its ability to help prevent and treat hypertension. It is balanced and can be followed long-term.
  • With its combination of unusually high fat plus remarkably low carb and fiber content, experts had enough reservations to place the Keto Diet way down in the best diets overall category. An editorial appearing online July 15, 2019, in JAMA Internal Medicine concluded that “enthusiasm outpaces evidence” when it comes to a keto diet for obesity and diabetes.
  • Slapping the Paleo Diet with multiple low scores, the experts couldn’t accept that entire food groups, like dairy and grains, as well as legumes are excluded, making it hard for dieters to get all the nutrients they need. Paleo was deemed too restrictive to be healthy or sustainable.
  • Experts dealt the Alkaline Diet mostly low scores, pronouncing it difficult to follow and noting that its nutrition profile isn’t ideal. One expert commented “This diet is ridiculous, poorly researched, and not based on science.”

Definitions Used in Rating the Diets

  • Short-term weight loss. Likelihood of losing significant weight during the first 12 months, based on available evidence (5 = extremely effective, 4 = very effective, 3 = moderately effective, 2 = minimally effective, 1 = ineffective).
  • Long-term weight loss. Likelihood of maintaining significant weight loss for two years or more, based on available evidence (5 = extremely effective, 4 = very effective, 3 = moderately effective, 2 = minimally effective, 1 = ineffective).
  • Diabetes. Effectiveness for preventing diabetes or as a maintenance diet for diabetics (5 = extremely effective, 4 = very effective, 3 = moderately effective, 2 = minimally effective, 1 = ineffective).
  • Heart. Effectiveness for cardiovascular disease prevention and as a risk-reducing regimen for heart patients (5 = extremely effective, 4 = very effective, 3 = moderately effective, 2 = minimally effective, 1 = ineffective).
  • Ease of compliance. Based on initial adjustment, satiety (a feeling of fullness so that you'll stop eating), taste appeal, special requirements (5 = extremely easy, 4 = very easy, 3 = moderately easy, 2 = somewhat difficult, 1 = extremely difficult).
  • Nutritional completeness. Based on conformance with the federal government's 2015-2020 Dietary Guidelines for Americans, a widely accepted nutritional benchmark (5 = extremely complete, 4 = very complete, 3 = moderately complete, 2 = somewhat complete, 1 = extremely incomplete).
  • Health risks. Including malnourishment, specific nutrient concerns, overly rapid weight loss, contraindications for certain populations or existing conditions, etc. (5 = extremely safe, 4 = very safe, 3 = moderately safe, 2 = somewhat unsafe, 1 = extremely unsafe).

Here is a link to the 2021 ratings by U.S. News and World Report.

Hats off to them for doing such a great job with this important annual project!


Best Diets, 2021. U.S. News and World Report.

*Overweight in adults is defined as a body mass index (BMI) between 25.0 and 29.9 kg/m2, while obesity is defined as a BMI greater than or equal to 30 kg/m2. Use this link to calculate your BMI. Please note that BMI is not a valid indicator of body weight status for individuals who are extremely muscular. However, such individuals make up only a tiny portion of the U.S. population.