Intermittent Fasting: The Science is Growing
Recent minor kurfuffle on MedPage about Intermittent Fasting. Response today:
Quote:
Intermittent Fasting: The Science is Growing
— Important to recognize that, when it comes to diet, one size does not fit all
by Michael Kelley, PhD
January 22, 2018
Earlier this month, a blog post by Suneel Kamath, MD, on intermittent fasting prompted many comments from readers and from diet and nutrition specialists contacted by MedPage Today. Kamath had criticized intermittent fasting as a fad diet with little evidence behind it regarding body weight, compared with traditional caloric restriction. We then heard from nutrition consultant Michael Kelley, PhD, who offered the following additional commentary.
My primary concern upon reading the article was the positioning of the science – the title positioned intermittent fasting as an oddity with scant scientific inquiry into effects on body weight and metabolism. Today, science must often contend with attempts to tell, and at times re-tell, the story of the science. Too often, an accurate portrayal of the science has been lost. I do not think this was Kamath's intent, but at the same time, the body of science was not accurately represented.
A systematic review by Seimon et al. in 2015 considered 12 clinical trials and concluded, "Intermittent fasting thus represents a valid -- albeit apparently not superior -- option to continuous energy restriction for weight loss." The entire review, which considered effects on appetite and metabolism, identified 72 potentially relevant publications, which were refined to 40 publications from 32 clinical studies.
In the more recent American Heart Association statement by St-Onge et al. in 2017, the authors wrote: "There is evidence that both alternate-day fasting and periodic fasting may be effective for weight loss, although there are no data that indicate whether the weight loss can be sustained long term." The 2017 clinical study by Trepanowski et al., reviewed by Kamath, came to a similar conclusion, albeit more conservatively stated.
Although Kamath did not cite further studies, his assessment of intermittent fasting for weight loss does reflect the overall literature. But the number of clinical studies on the topic currently stands at about 17 (depending on inclusion/exclusion criteria) and the body of scientific literature on intermittent fasting overall is several times larger. This is not "little evidence." This is serious and ongoing research performed by scientists who work mightily to gain scarce funding and publish the work. The goal is to provide the information which will ultimately guide our practice. Their efforts deserve an accurate portrayal.
Kamath then turned to an important issue: In practice, why consider intermittent fasting since the body weight effects appear to be no better than traditional caloric restriction?
One possible reason: individuals differ. For example, many in the U.S. have been raised with the concept of breakfast as an essential meal. With aging, some individuals seem to lose the desire for a meal consumed in the morning. An intermittent fasting meal pattern of 8 hours for consuming (e.g., noon to 8 p.m.) and 16 hours for fasting might work very well for some of these individuals -- for weight loss, or simply for weight maintenance and health. The proof would be in the results – it would be an experiment. (Note: There is a sizeable literature on the health effects of breakfast, including associations with body weight. This is beyond the scope of the present comments.)
The different practices of intermittent fasting may initially seem odd if the cultural norm is three or more meals per day. And while fasting may have been practiced and written about for centuries, it is difficult to determine the beginning of intermittent fasting practice beyond blog posts or web sites which appeared in the 1990's. I think this fails to qualify as a "fad," but it is certainly recent.
Those of us in the food and nutrition science world have observed the same frustrating trends Kamath expressed as a physician: Claims of wondrous health benefits resulting from various diets, foods, and ingredients. This growing flow comes direct to consumers via news reports, web sites, blogs, celebrity endorsements and an increasing number of social media channels. The sheer range of resulting questions can be daunting.
For healthcare providers, I think there are some anchors for guidance in a discussion with patients about intermittent fasting.
The MyPlate resources from the U.S. Department of Agriculture are based on the most current U.S. Dietary Guidelines. Although experts debate the evidence base and recommendations in the guidelines, for healthcare professionals in need of authoritative recommendations, it's hard to go wrong with the government guidelines as the basics for a healthy diet. The materials are consumer-friendly, so patients can reasonably be asked to read them.
Patients who want to experiment with their diet can be asked to confirm that the official recommendations be accounted for in the new diet plan. The guidelines recognize explicitly that there is not a single best practice when it comes to diet and that there is room to explore alternatives. The patient can be requested to return in the future to report on progress and issues, as in any situation where dietary change for health is implemented.
If any intermittent fasting-related fasting periods raise concerns regarding existing conditions or medications, the experts queried in the follow-up by MedPage Today have offered an initial source of guidance to augment the provider's expertise.
In the end, healthcare providers should not feel pressed to make an endorsement. If not comfortable with the description of intermittent fasting, or any recent dietary practice, it is reasonable to rely on the current dietary guidelines as the basic recommended practices, and when warranted, refer to a registered dietitian for more detailed guidance. Even with good sources of guidance, dietary change for any patient is an experiment, with a need for observation and follow-up.
Michael Kelley holds a BS, MS, and PhD in Nutrition Science, is a registered dietitian and holds an adjunct faculty appointment in the College of Dentistry at the University of Illinois in Chicago. He is a consultant who works on issues of nutrition science and health with food industry companies and industry associations, and develops continuing education content for health professionals. He is a member of the American Society for Nutrition and contributes to scientific programs and activities of the society. He previously held faculty positions at Emory University and San Diego State University, and as a scientist at Abbott Laboratories and The Wm Wrigley Jr Company (a subsidiary of Mars Inc.).
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For more detail on various time restricted eating plans, there is long thread about Dr Jason Fung's use of it to correct high blood sugars in diabetics: http://forum.lowcarber.org/showthread.php?t=472377 |