Gut Reaction #37: Intermittent Fasting

January 13, 2020 2

Following a month of indulgence, many decide to make lifestyle changes in January. Some try dietary restriction (eg ’Veganuary’) or reduce their total caloric intake, while others abstain from alcohol (eg ‘Dry January’) or jumpstart new exercise regimes. There are even some heroes among us making several changes at once. While it is advised that individuals take proper care of themselves year round, it is appreciated that this does not always happen.

Of topical interest therefore is that intermittent fasting proves beneficial for weight loss in both animal and human studies. As humans, we have not evolved to consume three large evenly-spaced meals throughout the day (plus snacks). This is a symptom of modern life and is due to an abundance of resources. Rather, we went for short stretches of time without food. We still needed to perform, to hunt prey and escape predators, but we did so in a fasted state.

Two methods of intermittent fasting in humans provide evidence-based weight loss, specifically the 5:2 regime (fasting 2 days per week), and daily time-restricted feeding (leaving, for example 18 hours between dinner and breakfast the next day, ie a 6-hour eating period). Comparatively, intermittent fasting seems to provide greater health benefits than a simple reduction in daily caloric intake, and might be considered the method of choice for effective weight control, metabolism of energy, and improved health across the lifespan.

Healthcare professionals may not understand how to prescribe intermittent fasting regimes. Patients may also be unwilling to start one. This may be due to several unpleasant short-term effects, such as increased levels of hunger and irritability, and decreased concentration. Ideally, a patient would ease into the plan over a number of months, in order to minimise any unpleasant effects. This allows time for the body to adjust. The following plans can be considered for 5:2 intermittent fasting and daily time-restricted feeding, respectively:

5:2 Intermittent Fasting

    • For month 1: 1000 calories 1 day per week
    • For month 2: 1000 calories 2 days per week
    • For month 3: 750 calories 2 days per week
    • For month 4: 500 calories 2 days per week

Daily Time-Restricted Feeding

    • For month 1: 10 hour feeding period 5 days per week
    • For month 2: 8 hour feeding period 5 days per week
    • For month 3: 6 hour feeding period 5 days per week
    • For month 4: 6 hour feeding period 7 days per week

A new year provides a convenient opportunity for a fresh start, and widespread participation and media coverage provides a sense of camaraderie between friends, family and colleagues. This may increase the odds of success, and if nothing else, at least everyone is miserable together. If you still find yourself feeling unsatisfied with any lifestyle changes you may have made in January, then what about trying ‘Fasting February’?

For more information, please contact Dr Adam Harris.


2 comments

  • Dr bill warrilow

    January 19, 2020 at 11:33 am

    What about Krista Varady’s alternate day fasting ? 500kcal alternating with ad libitum feeding? Her IF protocol has a substantially better research base than Moseley’s 5:2 protocol ( which he based on her work)

    As a GP I’ve found patients can get really excellent results with alternate day fasting

    5:2 has failed to work for most of my patients- it simply doesn’t restrict calorie intake enough to be effective it seems

    Reply

    • Dr Adam Harris

      January 19, 2020 at 3:52 pm

      Bill, thanks for your contribution. I suspect your patients will loose more weight on ADF as the total calorie intake each week will be lower than using 5:2. My patients, many of whom work in London, find it easier to fit 2 days of fasting into their working week and to eat normally at weekends.
      I am sure you will agree that most diets work if followed. Our task is to choose the right diet for the patient.

      Reply

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