I have often written about diets and fads.  No, I am not talking about keeping kosher, or the choices of vegetarian, vegan, or even pescatarian cuisine.  Generally, the best diets are the Mediterranean diet (here’s one such mention) and for those at risk of kidney failure, diabetes, even epilepsy, or traumatic brain injury, the keto diet.

But, I’ve always wondered about the fasting routine.

Sure, my religion (if one is extremely fastidious) requires 6 days of fasting every year.  And, our fasts are different from the fasts folks who use fasting as a diet routine.  Ours mean nothing crosses our lips- no food, no water, no tooth-brushing, etc.  The fasting diets mean only water is ingested.  (By the way, today is just one of those days- Asara B’Tevet, the 10th of the month of Tevet, to remind us of the Nevuchadnetzer’s [Nebuchadnezzar II of Babylonia] siege of Jerusalem, which led to the Babylonian destruction of King Solomon’s temple on the 9th of Av.)

But, if one is fasting as a means to lose weight- and is already overweight or obese and at risk of developing diabetes, is it a safe process?

A new, preliminary (read that word again, please!) study that Dr. Krista A Varady, along with the rest of her team at U Illinois-Chicago (K Gabel, CM Kroeger, JF Trepanowski, KK Hoddy, S Cienfuegos, and F Kalam) examination has been published in Obesity,   Differential Effects of Alternate-Day Fasting Versus Daily Calorie Restriction on Insulin Resistance.

The research monitored changes in fasting insulin, insulin resistance, BMI (body-mass index), fat mass, lean mass, among other parameters over a year.  43 adults (> 25 kg/m²   BMI  < 39.9 25 kg/m²), ranging in age from 18 to 65, with insulin resistance were the subject pool.  11 of the adults (81.8% women) were in the alternate-day fasting pool.  17 others (76.5% women) restricted their calories, with the remaining 15 continuing their normal diets (73.3% women).  All of the subject pools had a mean age in their very early 40s (41-43).

(Note that the current guidelines for caloric restriction for obese subjects is to lower their caloric intake by 20 to 30% a day from their basic energy needs.  As you can see, this study first determined each subjects ‘basic’ daily energy requirements.  All the diets in this protocol- except for the control- provided 30% of its energy as fat, 55% as carbohydrates, and 15% as protein.)

The diets (other than the control that continued their normal dietary regime) involved a 6 month weight loss phase, with a subsequent 6 month weight maintenance regime.

The alternate day fasters (ADF) stocked up on calories (125%) on day one, with only 25% ingested (basically a “normal” lunch) on day 2 for six months.  (Notice this was not a total fast!)  Then, for the maintenance phase,  the ratios were switched to 150% and 50%, respectively.

The caloric restricted group (CR) employed a diet that provided 75% of their energy requirements for the first phase, followed by one providing 100% of their energy requirements for the subsequent six months.

After the year’s program, the ADF group manifested weight losses of about 8% when compared to the control group.  Those with caloric restriction lost 6% of their weight when compared to the control group.

While that was not encouraging, there was a 52% reduction in fasting insulin levels for the ADF group and 14% for those with a calorie-restricted diet.  More importantly, the insulin resistance dropped by about the same levels for the ADF group.

Please note that this diet was more sensible than most of the “trendy’ fasting protocols, in that the fasting diet involved a conventional, healthy lunch as opposed to no food at all.   It’s also unclear if the subjects could have achieved the desired BMI (under 25) has the test diet had continued for longer periods.

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