Beyond “Counting Macros”: Are Common Fad Diets Nutritionally Adequate? An Examination of Their Micronutrient Content

Abstract

Abstract Objectives We compared a high-fiber bean-rich diet with a low-carbohydrate diet in a randomized controlled trial to assess their effects on body weight, blood lipids and micronutrient adequacy. Methods One hundred and seventy-three women and men with a mean body mass index of approximately 36 kg · m−2 were randomized to a high-fiber bean-rich diet that achieved mean (SD) fiber intakes of 35.5 (18.6) g · day−1 for women and 42.5 (30.3) g · day−1 for men, or a low-carbohydrate diet (<120 g · day−1). Both diets were induced gradually over 4 weeks and included a 3-day feeding phase. Results After 52 weeks, the low-carbohydrate (n = 24) group tended to retain weight loss better than the high-fiber group (n = 30) (P = 0.06), although total cholesterol remained lower with the bean-rich diet (P = 0.049). The low-carbohydrate group consumed more vitamin K (P = 0.006), thiamin (P = 0.001), and niacin (P = 0.02) whereas those in the high-fiber group consumed more folate (P = 0.006), magnesium (P = 0.046) and copper (P = 0.017). Both groups consumed less than the RDA for vitamin D, vitamin E, calcium, magnesium and copper. Conclusions A high-fiber bean-rich diet was as effective as a low-carbohydrate diet for weight loss. However, both diets were deficient in micronutrients. These results may have implications for long-term disease risk and morbidity management. Funding Sources Lifestyle Center of America (Sulphur, OK).