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Article Review: Effects of Intermittent Fasting on Insulin Sensitivity

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Identify the weight loss benefits and risks of intermittent fasting treatment
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Audio Transcript

Mark Labriola: Welcome to Obesity: A Disease, the official Obesity Medicine Association podcast exploring the many facets of the disease of obesity. In this series of podcasts, we have carefully selected recent articles included in the latest version in the OMA Obesity Algorithm. We then discuss this new science with obesity experts. I'm Mark Labriola, and in this episode, OMA Chief Science Officer Dr Harold Bays interview Dr Nick Pennings about the effects of intermittent vs. continuous energy on insulin sensitivity and metabolic risk in women with overweight. Obesity: A Disease podcast is brought to you by the Obesity Medicine Association, the clinical leader in obesity medicine.

Harold Bays: Today we are fortunate to have with us Dr Nicholas Pennings. Nick, why don't you tell the people who you are and what you do?

Nicholas Pennings: This is Nick Pennings, I am the Chair of Family Medicine at [1:00] Campbell University School of Osteopathic Medicine, and I am an Executive Director for Clinical Education at the Obesity Medicine Association and I have a particular research interest in the relationship between insulin, insulin resistance, and weight change.

HB: Well then, you're the perfect person for today's discussion, because we're going to be talking about an article in Obesity in 2019. The first author is Hutchinson and the name of the article is “Effects of Intermittent Fasting vs. Continuous [1:30] Energy Intakes on Insulin Sensitivity and Metabolic Risk in Women with Overweight.” This study aimed to compare the intermittent fasting versus continuous energy intakes at 100% or 70% of calculated energy requirements on insulin sensitivity, as well as a cardiometabolic risk and bodyweight composition, that sort of thing. The findings were that the intermittent fasting at 70% displayed greater reductions [2:00] in weight, fat mass, total and LDL cholesterol, and non-esterified fatty acid compared with not just the intermittent fasting 100%, but the decreased dietary intake of 70%. So their conclusion was when prescribed at matched energy restriction, intermittent fasting reduced weight and fat mass and improved total and LDL [2:30] cholesterol more than dietary restriction. So I found this to be very interesting because Nick, I think you probably have the same experience as me. There's an increasing number of clinicians and increased number of patients that have an interest in whether or not intermittent fasting is good for them. So when people have these questions and you see the study, what do you believe were some of the key findings of this analysis?

NP: Well, I think it was a very interesting study in the way that it was designed. [3:00] I think the four groups that you outlined are very interesting. It was a fairly small study, it was only 88 individuals and it was just women, so I think there's some limitations around that, but we need more study on intermittent fasting and understanding what is happening here. The study looked at intermittent fasting and defined it as going three out of seven days per week where they only consume breakfast and then didn't eat for 24 hours. So three consecutive days, [3:30] they'd have breakfast and then eat nothing until the next morning, and have breakfast again. And so that was the way it was constructed, and what was interesting about this is that those that had intermittent fasting of those three days at 70% of weekly caloric intake or reduced calorie intake did better than the group that reduced calories by the same amount, but spread them out evenly over the week.

HB: Yeah, well look, [4:00] intermittent fasting is nothing new. It's been going on since the beginning of time, I imagine, either for religious reasons or logistical reasons and challenges getting food on a consistent basis and such. But now that it's come to the forefront, now that it seems like something that's really catching on with a lot of folks and people want to know more about it—I mean I just got asked today of all things, asked a question about intermittent fasting. One of the questions [4:30] I was asked, “Does fasting, even intermittent fasting, result in compensatory overeating?” I mean, what's your sense about that?

NP: So from this I would say yes and no. So if you look at the one group that did intermittent fasting but consumed 100% of the calculated weekly intake, that that group tend to overeat, tend to consume more calories. So they would be given on their eating days [5:00] 145% of their normal calorie intake to make up for the difference that they were not eating on their fasting days, and so they did overeat. They did eat more than they normally would on those days. But no in the sense that they didn't eat everything that they could. So in the end, by the end of the week, they had consumed fewer calories than the control group, which had 100% of the calculated [5:30] weekly food requirement but distributed over seven days.

HB: So even though they had the option to eat as much as if they would have consumed the calories without the intermittent fasting, per day they eat a bit more but it still ended up being less for the week than they otherwise would have. Is that what you're saying?

NP: Right, it was about 9% less.

HB: Well, that's pretty good, right? Nine percent less?

NP: Yeah.

HB: So the next question [6:00] this woman asked me today, it was a clinician, and she said, “I'm really concerned that people that go on fasting, even intermittent fasting, that it might decrease my patient's metabolism. And I think what we know she meant is that she talked about a reducing the resting metabolic rate. You know what I described her was that anytime you lose body tissue, whether it be adipose tissue or muscle tissue or whatever, you don't require [6:30] as many and as much energy to sustain those tissues and so yes, there is going to be some reduction in the resting metabolic rate. But I think that another thing that concerned her was the possibility of a reduction in muscle mass for people that do fasting or intermittent fasting. What what's your sense about that?

NP: And that is a big area of controversy over that. Previous Studies have shown preservation of fat free mass with intermittent fasting. [7:00] But this study showed a loss of both fat mass and fat free mass, which is not uncommon in any weight-loss. This particular study didn't show preservation of that fat free mass, but there was loss of a fat free mass.

HP: And look, I think that's so important, such an important message to get across. I mean, we do a lot of, we do DEX analysis on patients who are undergoing weight reduction and when they look at their numbers, they see the percent body fat go down. They're very happy, [7:30] but then they find that their muscle mass has also decreased. And we just try to reassure them that that is so common, right? That's what you expect. It takes a really challenging exercise or physical activity program to prevent that loss of muscle when you're undergoing active weight loss. Has that been your experience?

NP: Absolutely.

HB: So in addition to effects upon body composition, [8:00] what was the impact on these metabolic parameters they looked at?

NP: So for the intermittent fasting group that had calorie restriction, so consuming 70% of weekly caloric requirement, they showed great improvement in total cholesterol, LDL cholesterol, glucose, and fasting insulin compared to the other groups, even compared to the daily calorie restriction at 70%. So the two groups that consumed the same amount of calories over the course of the week, the intermittent fasting [8:30] group had better improvement in those metabolic parameters.

HB: So what I'm hearing from you is there are some reasons to believe that in some patients, intermittent fasting is something to consider. So let me put it this way. Let's say a patient comes to someone listening, you know to a clinician listening to this program or maybe there's a patient listening to this programming. Let's just say they ask you, [9:00] and they say, “Dr Pennings, I'm thinking about doing intermittent fasting. Is that good or bad?” How do you answer them?

NP: So I think that depends on the individual, and I find that if a patient can restrict their calories or go through periods of fasting and not feel hungry, they feel comfortable with it—and particularly the patient that can go all day without eating and then eat at night—that that patient often does well with intermittent fasting. If somebody [9:30] misses a meal and they're feeling very hungry and really struggling with any missed meals, then that person may not be a good candidate for intermittent fasting.

HB: Right and oddly enough that's exactly what this clinician said to me, is “I really want to do this and I want to be supportive, but I've had patients who have done this and sometimes they don't feel well during the times that they're fasting.” I must, I must say that sometimes I get busy and I don't need and that doesn't really affect me very much, but it does affect some people. [10:00] Is that what I'm hearing from you?

NP: Right, that's what I find as well.

HB: Alright, well thank you very much, Dr Pennings. Thank you for being here.

ML: For more information about Obesity Medicine podcasts and other resources from the clinical leader in obesity medicine, please visit obesitymedicine.org/podcasts. Love this episode of Obesity: A Disease? Head over to iTunes to subscribe, rate, and leave a review. The views expressed in this podcast episode are those of the show hosts and do not necessarily represent the opinions, beliefs, or policies of the Obesity Medicine Association or its members. Please check back soon for another episode of Obesity: A Disease.

Audio Information

Disclosure Statement: Unless noted, all individuals in control of content reported no relevant financial relationships.

References
1.
Hutchinson  AT, Liu  B, Wood  RE, Thompson  CH, O'Callaghan  NJ, Wittert  GA, Hillibronn  LK.  Effects of Intermittent Versus Continuous Energy Intakes on Insulin Sensitivity and Metabolic Risk in Women with Overweight.  Obesity. 2019 Jan;27(1):50–58. doi: 10.1002/oby.22345.Google Scholar
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