The Fast Diet

March 19, 2013 Written by JP    [Font too small?]

Recently, a book bearing the title “The Fast Diet” was released in England. Thus far, sales of the book, co-authored by Dr. Michael Mosley, have been brisk and are likely to follow suit in the US where it was just published a few weeks ago. The underlying message of The Fast Diet is that adopting a 5:2 eating plan, in which you eat regularly for five days and semi-fast for two days, will reduce overweight and various risk factors associated with advanced aging, diabetes and heart disease. In the medical literature, this style of eating is commonly referred to as “intermittent fasting” (IF). Since the media and public have taken an interest in IF, I thought this would be a good opportunity to review the most current findings about this practice and a related form of dieting known as alternate day fasting (ADF) which calls for a semi-fast every other day.

Dr. Krista Varady, a friend of this site, is once again at the forefront of much of the latest research involving ADF and IF. For the most part, the scientific data continues to provide an optimistic view of programs that incorporate dietary restriction for a few to several days of the week. Some of the more intriguing studies report that: 1) Adding exercise to ADF enhances body fat and overall weight loss, while simultaneously conferring more impressive changes in cholesterol levels than alternate day fasting alone. 2) High fat ADF is as effective and safe as low fat ADF in relation to lowering cardiovascular risk and excess weight. 3) Short term, intermittent fasting during Ramadan decreases several pro-inflammatory cytokines, such as interleukin 1B, interleukin 6 and tumor necrosis factor a. 4) Intermittent fasting combined with a very low carbohydrate diet or ketogenic diet improves seizure control in otherwise treatment resistant epileptics.

Note: Alternate day fasting (ADF) typically permits about 500 calories on the 3 – 4 fast days of the week.

Also of interest is a study appearing in the October 2012 issue of the journal Nutrition & Metabolism. In it, Dr. Varady and several colleagues examined the relative effects of intermittent fasting (IF) with or without the use of liquid meal replacements. The design of the 10 week trial involved fasting on 120 calories of juice and water for one day of the week. On the six “feed days”, half of the study volunteers drank a protein-rich meal replacement for breakfast and lunch and ate a solid food meal for dinner. The remaining participants were asked to eat a calorically comparable diet consisting of solid food for all three meals. The authors of the study determined that those on the liquid IF diet lost a greater percentage of body fat and reduced waist circumference more than the participants eating three solid meals daily. The concluding remarks of the head-to-head comparison state that the, “liquid diet modulates visceral fat and adipokines in a way that may confer protection against coronary heart disease”. This finding offers yet another option for those who are interested in applying fasting in the most convenient and effective manner possible.

To learn more about the studies referenced in today’s column, please click on the following links:

Study 1 – The New York Time: England Develops a Voracious Appetite for a New (link)

Study 2 – Alternate Day Fasting and Endurance Exercise Combine to Reduce Body (link)

Study 3 – Alternate Day Fasting (ADF) w/ a High-Fat Diet Produces Similar Weight (link)

Study 4 – Intermittent Fasting During Ramadan Attenuates Proinflammatory(link)

Study 5 – Intermittent Fasting: A “New” Historical Strategy for Controlling (link)

Study 6 – Improvement in Coronary Heart Disease Risk Factors During an (link)

Study 7 – Intermittent Fasting Combined with Calorie Restriction is Effective for(link)

Higher Fat ADF Effectively and Safely Promotes Weight Loss

Source: Metabolism. 2013 Jan;62(1):137-43. (link)

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Posted in Alternative Therapies, Diet and Weight Loss, Nutrition

5 Comments & Updates to “The Fast Diet”

  1. rob Says:

    Fasting has become very trendy lately. Ive toyed with by not eating breakfast until a little later in the morning and by doing fasted workouts which have made it easier to lose a little more fat.

  2. JP Says:

    Hi Rob,

    Exercising on an empty stomach is a good approach to lowering blood sugar, leaning down and improving lipid profiles.

    While fasting is trendy these days, it’s also as old as time. We’re just applying it (and some are marketing it) in a slightly different way than our ancestors. 😉

    Be well!


  3. Jose Gonzalez Says:

    Hi! Great site.

    Look, regarding working out before breakfast, I’ve read articles that mention studies in Spain and Italy about the risk of having a heart attack for excersing in the early morning.

    What’s your view about it?

    Thanks a lot and best regards,


  4. JP Says:

    Hi Jose,

    I’m unaware of any cardiovascular risk. The primary concern I’ve read about is for those who are hypoglycemic. If that’s the case, then having an easily digestible protein-rich drink or snack (1/2 to 1 hour) prior to exercise would be advisable. Also, some people simply feel better when they eat a little something before a workout. This is an another instance where foregoing the “empty stomach” approach would likely be best.

    Be well!


  5. JP Says:

    Updated 12/21/16:

    Diabetes Res Clin Pract. 2016 Dec;122:106-112.

    The effects of intermittent compared to continuous energy restriction on glycaemic control in type 2 diabetes; a pragmatic pilot trial.

    AIMS: Weight loss improves glycaemic control in type 2 diabetes mellitus (T2DM). However, as achieving and maintaining weight loss is difficult, alternative strategies are needed. Our primary aim was to investigate the effects of intermittent energy restriction (IER) compared to continuous energy restriction (CER) on glycated haemoglobin A1c (HbA1c). Secondary aims were to assess effects on weight loss, body composition, medication changes and subjective measures of appetite. Using a 2-day IER method, we expected equal improvements to HbA1c and weight in both groups.

    METHOD: Sixty-three overweight or obese participants (BMI 35.2±5kg/m2) with T2DM (HbA1c 7.4±1.3%) (57mmol/mol) were randomised to a 2-day severe energy restriction (1670-2500kJ/day) with 5days of habitual eating, compared to a moderate CER diet (5000-6500kJ/day) for 12weeks.

    RESULTS: At 12weeks HbA1c (-0.7±0.9% P<0.001) and percent body weight reduction (-5.9±4% P<0.001) was similar in both groups with no group by time interaction. Similar reductions were also seen for medication dosages, all measures of body composition and subjective reports of appetite.

    CONCLUSIONS: In this pilot trial, 2days of IER compared with CER resulted in similar improvements in glycaemic control and weight reduction offering a suitable alternative treatment strategy.

    Be well!


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