Diets come and go, teasing and tempting with dreams of that elusive hot body. Eat what you want! Pounds melt away overnight! The reality, as frustrated dieters know well, is that dieting is hard, and frankly, most diets don’t work. Some can even threaten your health. And digging out the truth about dieting, let alone deciphering whether particular plans live up to the hype, is laborious enough to burn off a pound or two by itself.
Best Diets 2021 cuts through the clutter of claims. Now in its 11th year, Best Diets delivers the facts about and ranks 39 diets on a range of levels, from their heart healthiness to their likelihood to help you lose weight.
Many of the diets, like WW (Weight Watchers), are household names, while others, like the DASH (Dietary Approaches to Stop Hypertension) diet, should be. To create the latest edition of the rankings, U.S. News editors and reporters spent months winnowing potential additions to our diet roster and then mining medical journals, government reports and other resources to create in-depth profiles for those that made the cut.
Each profile explains how the diet works, determines whether its claims add up or fall short, scrutinizes it for possible health risks — and reveals what it’s like to live on the diet, not just read about it.
[See: Signs of Zinc Deficiency.]
A panel of nationally recognized experts in diet, nutrition, obesity, food psychology, diabetes and heart disease reviewed our profiles, added their own fact-finding and rated each diet in seven categories: how easy it is to follow, its ability to produce short-term and long-term weight loss, its nutritional completeness, its safety and its potential for preventing and managing diabetes and heart disease. We also asked the panelists to let us know about aspects of each diet they particularly liked or disliked and to weigh in with tidbits of advice that someone considering a particular diet should know.
After every diet received robust scrutiny, we converted the experts’ ratings to scores and stars from 5 (highest) to 1 (lowest). We then used those scores to construct nine sets of Best Diets rankings, which are as follows:
— Best Diets Overall combines panelists’ ratings in all seven categories. All categories were not equally weighted. Short-term and long-term weight loss were combined, with long-term ratings getting twice the weight. Why? Quick results are important after the holidays or when summer looms, but a diet’s true test is whether it can be sustained for years. That’s especially the case for those who are overweight or obese; losing as little as 5% of body weight can dramatically reduce the risk of chronic illnesses such as diabetes and heart disease. And safety was double-counted, because no diet should be dangerous.
— Best Commercial Diets uses the same approach to rank 15 structured diet programs that require a participation fee or promote the use of branded food or nutritional products.
— Best Weight-Loss Diets was generated by combining short-term and long-term weight-loss ratings, weighting both equally. Some dieters want to drop pounds fast, while others, looking years ahead, are aiming for slow and steady. Equal weighting accepts both goals as worthy.
— Best Diabetes Diets is based on averaged diabetes ratings.
— Best Heart-Healthy Diets uses averaged heart-health ratings.
— Best Diets for Healthy Eating combines nutritional completeness and safety ratings, giving twice the weight to safety. A healthy diet should provide sufficient calories and not fall seriously short on important nutrients or entire food groups.
— Easiest Diets to Follow represents panelists’ averaged judgments about each diet’s taste appeal, ease of initial adjustment, ability to keep dieters from feeling hungry and imposition of special requirements.
— Best Plant-Based Diets uses the same approach as Best Diets Overall to rank 12 plans that emphasize minimally processed foods from plants.
— Best Fast Weight-Loss Diets is based on short-term weight-loss ratings.
In all nine rankings, scores are rounded to one decimal place; diets with the same scores are ordered alphabetically.
In addition to the rankings, ratings in all seven categories are displayed for each diet as 1 to 5 stars on individual profile pages.
To ward off possible bias, each panelist provided information indicating clear or apparent conflicts of interest, like a paid consulting relationship with a company marketing a particular diet. In such cases, panelists did not rate the diet. For commercial programs offering a range of tracks that may target specific groups, such as pregnant women or those with diabetes, U.S. News selected the most mainstream version.
A vexing challenge faced us early on. To rate the diets, experts needed more than just labels like “short-term weight loss” and “health risk,” which can mean different things to different researchers. What should the standard be for rating nutritional soundness? What constitutes a health risk? Aided by the panelists and other experts, we settled on the following definitions to use 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 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 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).
We could not assign scores to the cost of a plan, nor to exercise. Even dieters buying prepackaged meals from commercial programs have to shop for at least some food, and individual shopping habits and preferences, not to mention dining out, will heavily determine any dieter’s total expense. Exercise gets serious attention in some diets and lip service in others, but the primary focus of a diet, after all, is food. Whether to exercise, how and how much is a lifestyle decision beyond the scope of a mere diet.
What’s next for Best Diets? We plan to scrutinize more eating plans and give dieters a way to plug in their personal preferences and requirements so they can zero in on diets that have the best chance of working for them. With diets, one size never fits all.