Long-Term Health Effects of the Three Major Diets Under Self-Management with Advice, Yields High Adherence and Equal Weight Loss, but very different Long-Term Cardiovascular Health Effects as Measured by Myocardial Perfusion Imaging and Specific Markers of Inflammatory Coronary Artery Disease

Abstract

Background: Obesity is caused by eating behaviours. Adherence to all diets has been extremely poor, thus, comparative data on health effects of different diets over periods of a year or more are limited. This study was designed to treat the root causes of obesity by modifying the eating behaviours and to compare the long-term (one year) cardiovascular health affects using three major diets under isocaloric conditions. Methods: 120 obese, otherwise healthy, adults were recruited including 63 men and 57 women with a mean age and BMI of 43.7 years and 42.4 respectively. Participants agreed to follow and self-manage diet with follow-up at six-week intervals to achieve 1500-1600 calorie intake of assigned diet type: low-to moderate-fat, lowered-carbohydrate, or vegan. Adherence, weight loss, changes in 14 cardiovascular lipids and coronary blood flow health risk indices were measured.Results: One-year body mass changes did not differ by diet (P>.999). Effect sizes (R, R2) were statistically significant for all indices. Coronary blood flow, R (CI95%) = .48 to .69, improved with low-to-moderate-fat and declined with lowered carbohydrate diets. Inflammatory factor Interleukin-6 (R = .51 to .71) increased with lowered carbohydrate and decreased with low-to-moderate-fat diets. Conclusion:One-year lowered-carbohydrate diet significantly increases cardiovascular risks, while a low-to-moderate-fat diet significantly reduces cardiovascular risk factors. Vegan diets were intermediate. Lowered-carbohydrate dieters were least inclined to continue dieting after conclusion of the study. Reductions in coronary blood flow reversed with appropriate dietary intervention. The major dietary effect on atherosclerotic coronary artery disease is inflammation and not weight loss.