Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Diabetes. Feb 15, 2020; 11(2): 26-32
Published online Feb 15, 2020. doi: 10.4239/wjd.v11.i2.26
Weight loss induced by whole grain-rich diet is through a gut microbiota-independent mechanism
Wen-Chi Wu, Akio Inui, Chih-Yen Chen
Wen-Chi Wu, Department of Medicine, Taipei Veterans General Hospital, Taipei 11217, Taiwan
Akio Inui, Pharmacological Department of Herbal Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima 890-8544, Japan
Chih-Yen Chen, Division of Gastroenterology and Hepatology, Department of Medicine, Taipei Veterans General Hospital, Taipei 11217, Taiwan
Chih-Yen Chen, Faculty of Medicine and Institute of Emergency and Critical Medicine, National Yang-Ming University School of Medicine, Taipei 11221, Taiwan
Chih-Yen Chen, Association for the Study of Small Intestinal Diseases, Taoyuan 33305, Taiwan
Chih-Yen Chen, Chinese Taipei Society for the Study of Obesity, Taipei 110, Taiwan
Author contributions: Chen CY conceived and designed the study; Wu WC reviewed the literature and wrote the manuscript; Chen CY, Inui A, and Wu WC made critical revisions and approved the final version of the manuscript.
Conflict-of-interest statement: The authors have no potential conflicts of interest to declare.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Chih-Yen Chen, AGAF, MD, PhD, Attending Doctor, Professor, Division of Gastroenterology and Hepatology, Department of Medicine, Taipei Veterans General Hospital, 201, Section 2, Shih-Pai Road, Taipei 11217, Taiwan. chency@vghtpe.gov.tw
Received: October 18, 2019
Peer-review started: October 18, 2019
First decision: November 6, 2019
Revised: November 22, 2019
Accepted: November 28, 2019
Article in press: November 28, 2019
Published online: February 15, 2020

The prevalence of overweight and obesity has increased worldwide. Obesity is a well-known risk factor of type 2 diabetes mellitus and cardiovascular disease and raises public health concerns. Many dietary guidelines encourage the replacement of refined grains with whole grains (WGs) to enhance body weight management. Current evidence regarding interrelationships among WGs, body weight, and gut microbiota is limited and inconclusive. In this editorial, we comment on the article by Roager et al published in the recent issue of the Gut 2019; 68(1): 83-93. In the study, obese patients (25 < body mass index < 35 kg/m2) were randomly assigned to receive two 8-wk dietary controlling periods with WGs and refined grain-rich diet. The results showed significantly decreased body weight in the WG group. Either the composition of gut microbiota or short-chain fatty acids, the leading end product of fermentation of non-digestible carbohydrate by gut microbiota, did not differ between the two groups. The study highly indicated that a WG-rich diet reduced body weight independent of gut microbiota. We then raised some plausible mechanisms of how WGs might influence body weight and demonstrated more literature in line with WGs enhance body weight control through a microbiota-independent pathway. Possible mechanisms include: (1) The abundant dietary fiber contents of WGs increase satiety, satiation, energy excretion from stool, and energy expenditure simultaneously decreasing energy absorption and fat storage; (2) The plentiful amount of polyphenols of WGs improve energy expenditure by hampering adipocyte maturation and function; (3) The sufficient magnesium and zinc of WGs guarantee lean body mass growth and decrease fat mass; (4) The effect of WGs on brown adipose tissue is a key component of non-shivering thermogenesis; and (5) The increase of adiponectin by WGs enhances glucose utilization, lipid oxidation, and energy expenditure.

Keywords: Whole grain, Obesity, Microbiota, Short-chain fatty acids, Brown adipose tissue, Adiponectin

Core tip: Obesity and its co-morbidity have caused worldwide public health concerns. Many countries recommend substituting whole grain (WG) for refined grain. Roager et al concluded that WGs reduce body weight through a microbiota-independent pathway. We suggest that the abundant dietary fibers, the plentiful amount of minerals and polyphenols of WGs, and possible effects on brown adipose tissue and adiponectin might take part in the weight loss caused by WG diet consumption.