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Published on 01.05.18 in Vol 20, No 5 (2018): May

Preprints (earlier versions) of this paper are available at http://preprints.jmir.org/preprint/8776, first published Aug 17, 2017.

This paper is in the following e-collection/theme issue:

    Letter to the Editor

    Authors’ Reply: Comment on “An Online Intervention Comparing a Very Low-Carbohydrate Ketogenic Diet and Lifestyle Recommendations Versus a Plate Method Diet in Overweight Individuals With Type 2 Diabetes: A Randomized Controlled Trial”

    1School of Nursing, Department of Health Behavior and Biological Sciences, University of Michigan, Ann Arbor, MI, United States

    2University of California, San Francisco, San Francisco, CA, United States

    3University of Michigan, Ann Arbor, MI, United States

    4University of California Berkeley, Berkeley, CA, United States

    5Institute of Holistic Health, Department of Health Education, San Francisco State University, San Francisco, CA, United States

    6Feinberg School of Medicine, Northwestern University, Chicago, IL, United States

    Corresponding Author:

    Laura Saslow, PhD

    School of Nursing

    Department of Health Behavior and Biological Sciences

    University of Michigan

    Room 2178, 400NIB

    Ann Arbor, MI,

    United States

    Phone: 1 (734) 764 7836

    Email: laura.saslow@gmail.com



    This letter is in response to the letter from Dr Andrew Reynolds [1] about our publication, “An Online Intervention Comparing a Very Low-Carbohydrate Ketogenic Diet and Lifestyle Recommendations Versus a Plate Method Diet in Overweight Individuals With Type 2 Diabetes: A Randomized Controlled Trial” [2].

    As Dr Reynolds notes, our study had several differences between the two groups including different diets, psychological tools, sleep education, and number of lessons.  Given the combination of intervention components, we did not attribute all of the differences in outcomes to the nutritional composition of the diet, but to the diet “and lifestyle recommendations.” It was our goal, if this preliminary trial showed promise, to follow up with factorial screening experiments to better assess each component of our multicomponent very low-carbohydrate diet intervention. We are currently testing our very low-carbohydrate diet intervention in this way, and we hope to vary the dietary component in future research. We agree that a randomized trial that varies only diet is an ideal way to ascertain to what extent the nutritional composition of the diet, specifically, contributes to the outcomes.

    However, important information can be learned about the overall effects of diet and lifestyle interventions without such screening experiments and intervention optimization. For example, the landmark Diabetes Prevention Program trial, with more than 3000 patients with prediabetes, compared a multicomponent low-fat, calorie-reduced diet and lifestyle intervention to metformin or medicine placebo groups [3]. The intact, multicomponent program is now used nationally, but to our knowledge, no research has carefully varied the dietary component to examine if the low-fat dietary recommendations are optimal. Despite this, this multicomponent program is supported by the Centers for Disease Control and Prevention and will be soon reimbursed by Medicare. Even so, we believe that the field needs to do more screening experiments and intervention optimization.

    We acknowledge the baseline differences on some of our outcome measures. This can happen even with classic randomized controlled trials. Nevertheless, our statistical evaluations emphasize interaction effects and, as such, they emphasize relative changes and fully incorporate baseline information. Therefore, we disagree that the interaction effects are due primarily to these baseline differences. With respect to a post-hoc power analysis, a power analysis reveals the likelihood of observing a significant effect. We disagree that once a study has been completed there is any value to a post-hoc power analysis. After study completion, we know for certain whether effects are significant (“power” = 100% for significant effects, and 0% for non-significant effects), and these results utilize observed variability rather than estimates of variability that would have informed a pre-study analysis.

    We agree that meta-analyses are ideal for judging the effects of different diets, however, we have a different interpretation of the meta-analysis to which he refers [4]. This meta-analysis of carbohydrate-restricted trials in type 2 diabetes itself notes that the “effect on glycemic control increased with the reported degree of carbohydrate restriction,” and that “recent trials suggest that LCD [low-carbohydrate diets] may be superior to HCD [high-carbohydrate diets] with respect to glucose level and postprandial excursions, but only as long as the subject adheres to the diet.” This suggests that when individuals can maintain adherence to long-term carbohydrate restriction they experience improved glycemic control. Moreover, only two of the seven studies in this meta-analysis followed participants beyond 12 months. We view this meta-analysis as support for the short-term benefits of low-carbohydrate diets in the treatment of type 2 diabetes, and that it highlights a need to conduct longer trials of low-carbohydrate diets that focus on long-term dietary adherence.

    We appreciate the opportunity to respond to Dr Reynolds’ letter.

    Conflicts of Interest

    Frederick Hecht is on the Scientific Advisory Board for Virta Health. No other author declares any conflict of interest.

    References

    1. Reynolds AN. Comment on “An Online Intervention Comparing a Very Low-Carbohydrate Ketogenic Diet and Lifestyle Recommendations Versus a Plate Method Diet in Overweight Individuals With Type 2 Diabetes: A Randomized Controlled Trial”. J Med Internet Res 2018;10(5):e180 [FREE Full text] [CrossRef]
    2. Saslow RL, Mason EA, Kim S, Goldman V, Ploutz-Snyder R, Bayandorian H, et al. An Online Intervention Comparing a Very Low-Carbohydrate Ketogenic Diet and Lifestyle Recommendations Versus a Plate Method Diet in Overweight Individuals With Type 2 Diabetes: A Randomized Controlled Trial. J Med Internet Res 2017 Feb 13;19(2):e36 [FREE Full text] [CrossRef] [Medline]
    3. Knowler WC, Barrett-Connor E, Fowler SE, Hamman RF, Lachin JM, Walker EA, Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002 Feb 07;346(6):393-403 [FREE Full text] [CrossRef] [Medline]
    4. Snorgaard O, Poulsen GM, Andersen HK, Astrup A. Systematic review and meta-analysis of dietary carbohydrate restriction in patients with type 2 diabetes. BMJ Open Diabetes Res Care 2017;5(1):e000354 [FREE Full text] [CrossRef] [Medline]

    Edited by G Eysenbach; This is a non–peer-reviewed article. submitted 17.08.17; accepted 18.08.17; published 01.05.18

    ©Laura Saslow, Ashley E Mason, Sarah Kim, Veronica Goldman, Robert Ploutz-Snyder, Hovig Bayandorian, Jennifer Daubenmier, Frederick M Hecht, Judith T Moskowitz. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 01.05.2018.

    This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in the Journal of Medical Internet Research, is properly cited. The complete bibliographic information, a link to the original publication on http://www.jmir.org/, as well as this copyright and license information must be included.