The HEI was created by the US Department of Agriculture to identify dietary factors associated with reduced CVD risk and to evaluate a plan’s potential to improve physiological states such as blood lipid levels and obesity (7
). The original HEI was inadequate to predict CVD mortality because it failed to distinguish between different types of carbohydrates and fats (26
). McCullough and colleagues (16
) devised the AHEI, and using data from the Nurses’ Health Study, found it was twice as good at predicting CVD as the HEI.
Findings using the AHEI and energy-adjusted AHEI were similar across plans. The Ornish plan, which is almost a completely vegetarian plan, scored high largely due to the amount of vegetables, fruit, cereal fiber intake, and low trans
). The Weight Watchers higher-carbohydrate and the New Glucose Revolution plans also fared well due to the emphasis on fruits and vegetables, higher whole-grain composition, and low trans
The Atkins/45-g carbohydrate plan had the lowest AHEI, because it was the lowest in fruit and cereal fiber and the highest in red meat and trans
fats. Recent metabolic studies showed detrimental effects of trans
fat on inflammatory factors and indicators of insulin resistance (35
). Epidemiologic studies have indicated that the magnitude of association between trans
fat and CVD is stronger than for saturated fat (36
). Over the longer term, the intake of saturated fat combined with high trans
fat may put dieters at risk. Although short-term studies have revealed a positive effect of the Atkins plan on CVD risk factors, including triglycerides (3
), the extent to which this effect is mediated by weight loss has yet to be elucidated. Weight loss independent of the diet, is associated with lipid reduction (38
). The longer-term effect of the Atkins plan on CVD risk is unknown because long-term studies have not been conducted (40
Both versions of Atkins’ plans had the highest intake of beneficial n-3 fatty acids (3.4 g/day); however, other fats affect the uptake and effect of protective n-3 fatty acids. The total saturated fat intake for the Atkins/45- and /100-g carbohydrate plans averaged 16.2% and 17.6% of total energy, respectively, in biologic competition with the beneficial effect of the n-3 fatty acids (41
). How this might affect longer-term dieters is unknown. For low saturated fat and higher n-3 intake, the 2005 Food Guide Pyramid and the New Glucose Revolution plans (<7% saturated fat, >1.8g/day n-3 fatty acid) fared the best.
The Institute of Medicine set an Adequate Intake value for fiber of 14 g per 1,000 kcal (43
) because high-fiber diets have been associated with decreased risk of CVD (22
). All plans achieved this target value. Total fiber (from all sources) was best achieved by the New Glucose Revolution (39.8 g/day) and Weight Watchers higher-carbohydrate plans (34.7 g/day).
The 2006 American Heart Association Scientific Statement recommends an upper limit of sodium intake of 2,300 mg/day for healthy individuals and lower for individuals with concerns such as hypertension (25
). The 2005 Food Guide Pyramid plan and the Atkins/100-g carbohydrate plan contained the highest intakes of sodium, both above the American Heart Association limit, at 2,386±704 mg/day, and 2,539±830 mg/day, respectively.
An unexpected finding was that after adjusting for energy content, the 2005 Food Guide Pyramid plan, which is based on the Dietary Guidelines for Americans 2005
), fared significantly worse than the New Glucose Revolution, Weight Watchers higher carbohydrate, and Ornish plans. The 2005 Food Guide Pyramid plan was devised to prevent nutrient deficiencies. Nutrient deficiencies relate to physiological requirements, but are not an objective measure that correlates with the prevention of CVD. The intake of protective nutrients must be balanced in an overall dietary pattern that addresses both excess and deficiency. Compared to the 2005 Food Guide Pyramid plan, New Glucose Revolution, Weight Watchers high carbohydrate, and Ornish incorporate much higher levels of fruit and vegetable consumption, which accounted for much of the difference in AHEI scores. Diets rich in fruit and vegetable consumption are recommended by the American Heart Association Nutrition Committee (25
), but whether or not increasing fruit and vegetable consumption from seven combined daily servings (as in the 2005 Food Guide Pyramid plan) to 11 (as in the New Glucose Revolution plan) would further reduce CVD risk is not known.
The plans assessed varied greatly in daily energy content (from 1,025 kcal to 1,946 kcal) and degree of restriction of macronutrients. The Zone and Weight Watchers high-protein plans scored high on the AHEI; however, were below 1,200 kcal, which may affect adherence. For example, in one study, participants on the Zone diet consumed 1,393 kcal daily, 368 kcal more than the recommended 1,025 kcal (6
). Although many plans work equally well for weight loss (6
), dietary quality should be considered when selecting a weight-loss plan, particularly patients at risk for CVD. Both weight loss and nutrition needs maximize health potential.
Our study has several limitations. First, the analyses assumed perfect adherence to dietary recommendations. Future research should assess the quality of weight-loss plans as they are carried out, an approach that would account for deviations in adherence. Second, only eight popular weight-loss plans were analyzed. Third, dietary supplements were not included in the analyses. Fourth, in the AHEI validation study (16
), the “major chronic disease” deaths were from CVD or cancer. Thus, the AHEI has not been validated for chronic disease in general. Fifth, the AHEI does not account for energy, which can affect adherence. Finally, only 7 days of menus were entered for each plan. Thus, the study may be underpowered to detect all of the plan differences, which is why an error correction procedure (eg, Bonferroni) was used in multiple comparison analyses.