Affiliation:
1. Department of Nutritional Sciences, Faculty of Medicine, University of Toronto; and with the Division of Endocrinology & Metabolism; the Department of Medicine; the Li Ka Shing Knowledge Institute; and the Toronto 3D Knowledge Synthesis & Clinical Trials Unit, Clinical Nutrition and Risk Factor Modification Centre; St. Michael’s Hospital, Toronto, Ontario, Canada
Abstract
Abstract
Carbohydrates are increasingly being implicated in the epidemics of obesity, diabetes, and their downstream cardiometabolic diseases. The “carbohydrate-insulin model” has been proposed to explain this role of carbohydrates. It posits that a high intake of carbohydrate induces endocrine deregulation marked by hyperinsulinemia, leading to energy partitioning with increased storage of energy in adipose tissue resulting in adaptive increases in food intake and decreases in energy expenditure. Whether all carbohydrate foods under real-world feeding conditions directly contribute to weight gain and its complications or whether this model can explain these clinical phenomena requires close inspection. The aim of this review is to assess the evidence for the role of carbohydrate quantity vs quality in cardiometabolic health. Although the clinical investigations of the “carbohydrate-insulin model” have shown the requisite decreases in insulin secretion and increases in fat oxidation, there has been a failure to achieve the expected fat loss under low-carbohydrate feeding. Systematic reviews with pairwise and network meta-analyses of the best available evidence have failed to show the superiority of low-carbohydrate diets on long-term clinical weight loss outcomes or that all sources of carbohydrate behave equally. High-carbohydrate diets that emphasize foods containing important nutrients and substances, including high-quality carbohydrate such as whole grains (especially oats and barley), pulses, or fruit; low glycemic index and load; or high fiber (especially viscous fiber sources) decrease intermediate cardiometabolic risk factors in randomized trials and are associated with weight loss and decreased incidence of diabetes, cardiovascular disease, and cardiovascular mortality in prospective cohort studies. The evidence for sugars as a marker of carbohydrate quality appears to be highly dependent on energy control (comparator) and food source (matrix), with sugar-sweetened beverages providing excess energy showing evidence of harm, and with high-quality carbohydrate food sources containing sugars such as fruit, 100% fruit juice, yogurt, and breakfast cereals showing evidence of benefit in energy-matched substitutions for refined starches (low-quality carbohydrate food sources). These data reflect the current shift in dietary guidance that allows for flexibility in the proportion of macronutrients (including carbohydrates) in the diet, with a focus on quality over quantity and dietary patterns over single nutrients.
Funder
PepsiCo, Nestlé, Wilmar, Amway, McDonald's, and Starbucks
Canadian Foundation for Innovation, Ontario Research Fund
Province of Ontario Ministry of Research and Innovation and Science
Canadian Institutes of Health Research
CIHR
Diabetes Canada, PSI Foundation, Banting & Best Diabetes Centre
American Society for Nutrition
Dried Fruit Council Foundation
National Dried Fruit Trade Association
Tate & Lyle Nutritional Research Fund
University of Toronto
Glycemic Control and Cardiovascular Disease in Type 2 Diabetes Fund
Nutrition Trialists Fund at the University of Toronto
Publisher
Oxford University Press (OUP)
Subject
Nutrition and Dietetics,Medicine (miscellaneous)