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  • private debate over fasting

    So a friend of mine and I have different views on fasting and time restricted feeding. I like to follow the basics on nutrition (adequate calories, protein and fiber) while my best friend swears on the benefits of fasting. He has sent me numerous articles and studies on the benefits of fasting such as mood, elevated cognition, and lowering risk of certain diseases. Since we are both not experts on the subject matter I told him I would ask in the forum about other possible benefits to fasting other than just weight loss.

    Have you read any articles or studies proposing benefits of fasting on life longevity, lower risk of cancer and heart disease, and elevating cognitive respose and mood? If so, what is your take on these studies? It seems like something hard to test since the studies would have to yake data on subjects for an extended period of their life..also, could you send me any links on findings we can use to inform our decision? we are both open to changing our minds on the subject but we don't know enough about studies and evidence on the matter. Thanks again

  • #2
    Yes. You should sign up for our newsletter, as this was in the May edition
    Intermittent fasting and intermittent energy restriction have been getting a lot of attention lately as potential interventions for weight loss with many claiming improved results over regular eating schedules. This month, let's take a look at what the scientific evidence has to say about these two strategies.

    Let's start with some definitions:
    • Intermittent fasting has many different flavors including time-restricted eating periods (e.g. a 16:8 ratio where an individuals fasts for 16 hours and consumes all daily calories within 8 hours), alternate day fasting (e.g. where people eat one day and fast the next to achieve a particular calorie level over the course of the week), and other types of eating schedules where individuals fast for extended periods of time.
    • Intermittent energy restriction also takes many different forms, but it is typically described as a ratio of week "on" (e.g. calorie restriction) to weeks "off" (e.g. calorie maintenance). For example, a 1:1 ratio would denote 1 week of calorie restriction followed by 1 week of calorie maintenance, whereas a 2:2 ratio would denote 2 weeks of calorie restriction followed by 2 weeks of maintenance calorie intake.
    Overall, the big difference between intermittent fasting proper and intermittent energy restriction in the context of weight loss is the duration of the calorie restriction. Whereas intermittent fasting is a type of day-to-day strategy for producing a continuous calorie deficit, intermittent energy restriction is a strategy where the individual goes through phases of calorie deficits followed by "breaks" where the individual is to consume maintenance calories. We'll discuss both of these strategies below, starting with intermittent fasting.


    A recent systematic reviews Harris et al. looked at how intermittent fasting stacked up to either traditional calorie restriction (e.g. reducing calorie intake by 25%) or no intervention in overweight or obese individuals. A total of 6 studies met inclusion criteria for this meta analysis, which ultimately included studies ranging 3-12 months and just under 200 subjects. Nevertheless, intermittent fasting didn't do any better than traditional eating patterns with respect to weight loss, as both groups lost about 7kg. Not surprisingly, intermittent fasting did do better than the control group, which did not restrict calories.

    A second meta-analysis by Headland et al. compared intermittent fasting to traditional eating schedules and their effects on weight loss included 9 studies and just under 1000 subjects. Again, there were no statistically significant differences in average weight loss achieved between the intermittent fasting and traditional eating schedule arms in this analysis.

    Additionally, attrition rates were similar in both arms, which suggests that intermittent fasting may not be easier to adhere to for everyone. Finally, a direct quote from the authors regarding health outcomes and intermittent fasting:

    "Currently there is insufficient data to support the notion that IER (in any form) can affect CVD risk markers (i.e., blood pressure and blood lipid levels) or insulin and glucose to a greater extent than that seen with CER. Moreover, changes in HbA1c or insulin sensitivity levels beyond weight loss have not been established. Further investigations into this are needed."

    Next, let's talk about intermittent energy restriction, specifically The MATADOR (Minimising Adaptive Thermogenesis And Deactivating Obesity Rebound) study by Byrne et al. This study has been getting a lot of attention, as the results suggested a huge advantage for intermittent energy restriction over continuous energy restriction. Let's take a look at the results:
    • Fifty-one obese men were randomized to either 16 weeks of continuous energy restriction or eight 2-week periods of energy restriction followed by 2-week maintenance calorie periods (total of 30 weeks).
    • Those who were randomized to the intermittent energy restriction group lost an average of 14.1kg over the 30 weeks. During the 2-week maintenance periods, weight loss was minimal (0.0±0.3 kg).
    • Those in the continuous energy restriction group lost an average of 9.1kg over the 16 weeks.
    The authors then tried to figure out why the individuals in the intermittent group did better than those in the continuous group. One theory had to do with the changes in resting metabolic rate (RMR).

    Resting metabolic rate (RMR) typically constitutes 60–75% of total daily energy expenditure (TDEE) and is a function of body mass- mainly fat-free mass, but also includes a small contribution from fat mass.
    Subsequently, weight loss tends to cause a decline in RMR via the loss of both fat-free and fat mass. That said, weight-loss-induced reductions in RMR—which occur in both lean and obese individuals—tend to exceed what is predicted by decreases in fat-free mass and fat mass alone due to a process called adaptive thermogenesis.

    Adaptive thermogenesis is a metabolic alteration the reduces the degree of energy deficit achieved by energy restriction by reducing "non-exercise activity thermogenesis", or NEAT. NEAT refers to all activity, muscle twitches, etc. that are not exercise.

    In the MATADOR study, the authors hypothesized that weight loss would be greater with intermittent energy restriction vs continuous energy restriction, in part because of attenuation of adaptive thermogenesis (smaller reduction in RMR) by using the intermittent strategy. response to intermittent energy.

    Indeed, RMR reductions showed a significant difference between groups when adjusted for changes in body composition, as the intermittent group saw a ~119 Calorie per day reduction in RMR as compared to the 149 Calorie per day reduction in RMR seen in the continuous group. 30 Calories, y'all.

    I'm not sure if I can get excited about that, though the increased weight loss in the intermittent group certainly is interesting. One might consider other reasons that the intermittent group did better than the continuous group:
    • Increased levels of calorie restriction in the intermittent group as compared to the continuous group
    • More total time spent being involved in a weight loss study for the intermittent group compared to the continuous group
    • More physical activity in the intermittent group as compared to the continuous group
    • Increased levels of compliance with the prescribed calorie restriction in the intermittent group as compared to the continuous group
    • Inter-individual differences in weight loss, which can certainly alter the results in a relatively small study like this
    • The 30 Calorie/day difference between methods is legit
    When addressing these based on data, it doesn't seem likely that either increased compliance with calorie restriction or greater calorie restriction in general is seen with intermittent energy restriction compare to continuous energy restriction, as reviews by Cioffi, Harris, and Headland all suggest this does not reliably happen.

    Additionally, the RMR difference of 30 Calories per day between continuous and intermittent energy restriction seems highly unlikely to be relevant or even reliable, as the review by Cioffi reports:

    "...the reduction in resting energy expenditure, i.e. the compensatory metabolic response which reduces the degree of weight loss, has been reported to be either reduced (favoring weight loss) or increased (attenuating weight loss) with intermittent energy restriction regimens. Indeed, some studies suggest that intermittent energy restriction evokes the same adaptive response as continuous energy restriction."

    Overall, my take on intermittent fasting and intermittent energy restriction is that they can be viable strategies for some individuals to lose weight if they prefer either (or both). That said, neither intermittent fasting nor intermittent energy restriction appear to have any additional health benefits based on the existing evidence and it certainly cannot be viewed as a panacea for health improvement.


    References

    Byrne NM, Sainsbury A, King NA, Hills AP, Wood RE. Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR study. Int J Obes (Lond). 2018;42(2):129–138. doi:10.1038/ijo.2017.206

    Cioffi I, Evangelista A, Ponzo V, et al. Intermittent versus continuous energy restriction on weight loss and cardiometabolic outcomes: a systematic review and meta-analysis of randomized controlled trials. J Transl Med. 2018;16(1):371. Published 2018 Dec 24. doi:10.1186/s12967-018-1748-4

    Harris, L., Hamilton, S., Azevedo, L. B., Olajide, J., De Brún, C., Waller, G., … Ells, L. (2018). Intermittent fasting interventions for treatment of overweight and obesity in adults. JBI Database of Systematic Reviews and Implementation Reports, 16(2), 507–547. doi:10.11124/jbisrir-2016-003248

    Headland M, Clifton PM, Carter S, Keogh JB. Weight-Loss Outcomes: A Systematic Review and Meta-Analysis of Intermittent Energy Restriction Trials Lasting a Minimum of 6 Months. Nutrients. 2016;8(6):354. Published 2016 Jun 8. doi:10.3390/nu8060354
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    • #3
      I read this in the newsletter, but we are actually asking about other benefits besides weight loss. There are many claims connected to studies and journals that fasting can boost mood, cognitive function, extend life, and lower diseases such as cancer, heart related diseases and diabetes. There seems to be quite a few of them on various research publications and I thought maybe you could address some of these other claims. Weight loss is not an issue or concern for either of us.

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      • #4
        In the article I write:

        "Currently there is insufficient data to support the notion that IER (in any form) can affect CVD risk markers (i.e., blood pressure and blood lipid levels) or insulin and glucose to a greater extent than that seen with CER. Moreover, changes in HbA1c or insulin sensitivity levels beyond weight loss have not been established. Further investigations into this are needed."


        I'm not aware of any studies objectively showing improvements in mood, cognitive performance, but the cancer/CVD/Diabetes is not supported.

        The citations provided include the latest meta analyses. In short, your friend is mistaken as I addressed in the article
        Barbell Medicine "With you from bench to bedside"
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