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Comment & Response
December 2019

Ketogenic Diets for Diabetes and Obesity

Author Affiliations
  • 1UCSF Osher Center for Integrative Medicine, University of California, San Francisco
JAMA Intern Med. 2019;179(12):1734. doi:10.1001/jamainternmed.2019.5108

To the Editors Although Joshi and colleagues’ Viewpoint on ketogenic diets1 for diabetes and obesity makes an important point that enthusiasm for these diets has outstripped evidence, I have 2 concerns. First, the authors fail to call for high-quality research to address this enthusiasm gap. Some of the hype has occurred because there is evidence that these diets can improve glycemic control in diabetes for a sustained period of time. Our own clinical trial2 showed statistically (and clinically) significant improvements in glycated hemoglobin levels at 12 months. We recognize, however, that larger trials with longer follow-up are crucial. But, as far as I am aware, there has not been sufficient funding for such research. A search for National Institutes of Health (NIH)-funded studies on low-carbohydrate or ketogenic diets (NIH RePORTER; August 2, 2019) suggests that there are currently no studies funded on diabetes and such diets. Without a clear call for appropriate research, the authors fail to address a root cause for why enthusiasm outpaces evidence: the lack of publicly funded research support for studies to clarify the risks and benefits of ketogenic diets for diabetes. Although there may be multiple reasons for this, there is a strong perception in the field that review committees in diabetes nutrition at NIH have been dominated by reviewers who are resistant to funding research on low-carbohydrate diets, regardless of the quality of the science involved. Whatever the cause, this research deficit seems important to address. Second, the authors’ list of adverse events associated with ketogenic diets relies on an uncontrolled, retrospective medical record review of children on ketogenic diets for epilepsy (substantially more restrictive than ketogenic diets for diabetes), in which any ill health condition that occurred was attributed to the diet.3 Higher-quality data from randomized clinical trials do not support a causal relationship between ketogenic diets for diabetes and most of the adverse events listed. The authors also seem to have limited knowledge about the composition of ketogenic diets for diabetes and obesity because they claim that one of the greatest risks is the “opportunity cost of not eating high-fiber, unrefined carbohydrates.”1(1164) Many well-designed ketogenic diets, including those we have studied, emphasize replacing carbohydrates with foods such as green leafy vegetables, fish, nuts, seeds, and olive oil. These foods permit as high a fiber diet as one containing unrefined carbohydrates, with a much lower glycemic load, and emphasize foods with stronger evidence for health benefits.

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