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Dietary carbohydrate restriction improves metabolic syndrome independent of weight loss
Parker N. Hyde, … , Ronald M. Krauss, Jeff S. Volek
Parker N. Hyde, … , Ronald M. Krauss, Jeff S. Volek
Published June 20, 2019
Citation Information: JCI Insight. 2019;4(12):e128308. https://doi.org/10.1172/jci.insight.128308.
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Clinical Research and Public Health Metabolism

Dietary carbohydrate restriction improves metabolic syndrome independent of weight loss

Abstract

BACKGROUND Metabolic syndrome (MetS) is highly correlated with obesity and cardiovascular risk, but the importance of dietary carbohydrate independent of weight loss in MetS treatment remains controversial. Here, we test the theory that dietary carbohydrate intolerance (i.e., the inability to process carbohydrate in a healthy manner) rather than obesity per se is a fundamental feature of MetS.METHODS Individuals who were obese with a diagnosis of MetS were fed three 4-week weight-maintenance diets that were low, moderate, and high in carbohydrate. Protein was constant and fat was exchanged isocalorically for carbohydrate across all diets.RESULTS Despite maintaining body mass, low-carbohydrate (LC) intake enhanced fat oxidation and was more effective in reversing MetS, especially high triglycerides, low HDL-C, and the small LDL subclass phenotype. Carbohydrate restriction also improved abnormal fatty acid composition, an emerging MetS feature. Despite containing 2.5 times more saturated fat than the high-carbohydrate diet, an LC diet decreased plasma total saturated fat and palmitoleate and increased arachidonate.CONCLUSION Consistent with the perspective that MetS is a pathologic state that manifests as dietary carbohydrate intolerance, these results show that compared with eucaloric high-carbohydrate intake, LC/high-fat diets benefit MetS independent of whole-body or fat mass.TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT02918422.FUNDING Dairy Management Inc. and the Dutch Dairy Association.

Authors

Parker N. Hyde, Teryn N. Sapper, Christopher D. Crabtree, Richard A. LaFountain, Madison L. Bowling, Alex Buga, Brandon Fell, Fionn T. McSwiney, Ryan M. Dickerson, Vincent J. Miller, Debbie Scandling, Orlando P. Simonetti, Stephen D. Phinney, William J. Kraemer, Sarah A. King, Ronald M. Krauss, Jeff S. Volek

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Carbohydrate Quality Matters

Submitter: Shivam Joshi | shivam.joshi@nyulangone.org

Authors: Shivam Joshi, Robert J. Ostfeld, Garth Davis, and Michelle McMacken

New York University School of Medicine

Published September 7, 2019

Hyde et al. recently published a crossover trial of 16 obese individuals randomized to four-weeks of consuming a low-, moderate-, or high-carbohydrate diet that appears to have shown that carbohydrate restriction improveed metabolic syndrome independent of weight loss (1). However, a closer examination of the foods consumed in the high-carbohydrate group reveals that the majority of those carbohydrates were from refined sources or added sugars. For example, based on the sample meal plan provided in the supplement, those in the high-carbohydrate group consumed 151.2 grams of sugar per day, which was notably higher than the moderate-carbohydrate (73.9 g/day) and low-carbohydrate groups (15.2 g/day). Of the sugars consumed in the high-carbohydrate group, most of the sugars (70.83%) were attributable to added or isolated sugars from juices (36.3%), sauces (10.7%), or other processed foods (23.7%), including marshmallow fluff and Fig Newtons. Similarly, 58.8% of the carbohydrates in the high-carbohydrate diet were refined, from highly processed foods such as cinnamon life cereal, pretzels, sauces, and juices. Although these refined carbohydrates are perhaps examples of foods commonly consumed in the American diet, they are by no means a comprehensive, let alone a desired, sample of carbohydrates available. Accordingly, highly refined carbohydrates have been implicated in causing and worsening metabolic syndrome – a finding that is not novel (2, 3). Hence, it is not surprising that the “high-carbohydrate” diet utilized in this study worsened parameters of the metabolic syndrome. Conversely, unrefined carbohydrates from whole grains, legumes, and whole fruits have been associated with lower rates of metabolic disease but only constituted 6.2% of the carbohydrates consumed in the sample diet (4-9).  Furthermore, unrefined carbohydrates have been repeatedly associated with healthful outcomes (10).

The predominance of poor-quality carbohydrates in the high-carbohydrate arm of this study appear to nullify the clinical significance of the study findings. It is unfortunate that carbohydrate quality was not assessed or discussed by Hyde et al., especially given the well-known importance of carbohydrate quality in health. It is also noted that several of the authors had financial conflicts of interest with low-carb entities and that funding of the experiment came from “National Dairy Council and the Dutch Dairy Association to The Ohio State University.”

Disclosures: Dr. Ostfeld reported receiving a research grant from the Purjes Foundation.

References

1. Hyde PN, Sapper TN, Crabtree CD, et al. Dietary carbohydrate restriction improves metabolic syndrome independent of weight loss. JCI insight. 2019;4(12).

2. AlEssa HB, Bhupathiraju SN, Malik VS, et al. Carbohydrate quality and quantity and risk of type 2 diabetes in US women. Am J Clin Nutr. 2015;102(6):1543-53.

3. Sluijs I, van der Schouw, Yvonne T, van der A, Daphne L, et al. Carbohydrate quantity and quality and risk of type 2 diabetes in the European prospective investigation into cancer and Nutrition–Netherlands (EPIC-NL) study. Am J Clin Nutr. 2010;92(4):905-11.

4. Becerra-Tomás N, Díaz-López A, Rosique-Esteban N, et al. Legume consumption is inversely associated with type 2 diabetes incidence in adults: A prospective assessment from the PREDIMED study. Clinical Nutrition. 2018;37(3):906-13.

5. Sievenpiper JL, Kendall C, Esfahani A, et al. Effect of non-oil-seed pulses on glycaemic control: A systematic review and meta-analysis of randomised controlled experimental trials in people with and without diabetes. Diabetologia. 2009;52(8):1479-95.

6. Mollard RC, Luhovyy BL, Panahi S, Nunez M, Hanley A, Anderson GH. Regular consumption of pulses for 8 weeks reduces metabolic syndrome risk factors in overweight and obese adults. Br J Nutr. 2012;108(S1):S111-22.

7. Ye EQ, Chacko SA, Chou EL, Kugizaki M, Liu S. Greater whole-grain intake is associated with lower risk of type 2 diabetes, cardiovascular disease, and weight gain. J Nutr. 2012;142(7):1304-13.

8. Aune D, Norat T, Romundstad P, Vatten LJ. Whole grain and refined grain consumption and the risk of type 2 diabetes: A systematic review and dose–response meta-analysis of cohort studies. Eur J Epidemiol. 2013;28(11):845-58.

9. Du H, Li L, Bennett D, et al. Fresh fruit consumption in relation to incident diabetes and diabetic vascular complications: A 7-y prospective study of 0.5 million Chinese adults. PLoS Medicine. 2017;14(4):e1002279.

10. Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L. Carbohydrate quality and human health: A series of systematic reviews and meta-analyses. The Lancet. 2019;393(10170):434-45.

 

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