• 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 11 plans that emphasize minimally processed foods from plants.
In all eight 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 its individual profile page.
To ward off possible bias, each panelist provided information indicating clear or apparent conflicts of interest, such as 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 something different 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 Dietary Guidelines for Americans 2010, 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).