Saturday, July 6, 2013

The Nutrition Debate #123: Intermittent Fasting and “The 23-hour IF Diet”

“IF” is not a conjunction introducing a conditional clause.” As most dieters know, “IF” means Intermittent Fast or Intermittent Fasting. Intermittent Fasting is a well-known method of dieting that is very popular with those who can tolerate it. They are generally people who are keto-adapted, which permits them to do it easily without hunger. It is also used by some who are able to endure hunger or even like to feel a little hungry, perhaps on the theory that denial is virtuous and demonstrates self-control. It appeals and “feels right” to others as a throwback to ancestral times when food was generally scarce, and hunters and gatherers ate less in the winter and more “in season” and bountiful times.

 “Intermittent” means “coming and going at intervals,” “not continuous,” or “occasional.” It is open to interpretation. Duration and frequency of intermittence are also not defined. “Fast” is also open to interpretation but generally means a period in which no calories are consumed during the fasting period. In common usage when applied to the human diet, that definition is sometimes stretched to include water and low-calorie beverages such as black coffee and plain tea. Personally, only breakfast coffee and water “cuts it” with me.  Then, I “gird my loins” and “go whole-hog,” to horribly mix my metaphors. But just skipping dinner once or twice a week can have miraculous effects without much effort.

According to the Wikipedia entry, “There is evidence suggesting that intermittent fasting may have beneficial effects on the health and longevity of animals – including humans – that are similar to the effects of caloric restriction.” For more on CR, see The Nutrition Debate #79 , #81 , and #82. The myriad health and longevity benefits have mostly been seen in animals (e.g., rats and worms). They include: reduced serum glucose and insulin levels, increased resistance of neurons to stress in the brain, reduced blood pressure, increased insulin sensitivity, and increased heart rate variability; also: increased resistance of heart and brain cells to ischemic injury and age-related deficits in cognitive function. As with CR, IF has often been associated with increased lifespan ranging in one study (male rats fasting 1 day in 3) of 20%. Another study in worms increased lifespan from 40% to 57% for alternate day fasting and 2-in-3 day fasting, respectively.

Intermittent fasting has mostly been adopted by humans as a weight-loss tool. There are, however, myriad ancillary benefits. Check out this Wikipedia entry on Calorie Restriction. Historically, periodic fasting is also an important part of various religious traditions. Recall Ecclesiastes 3: 1: “There is a time for everything, and a season for every activity under the heavens…” My favorite bible quote though is from Luke 4:23. Jesus said “Physician, heal thyself.” Hippocrates, who centuries before Christ created the Physician’s credo “First, do no harm,” must be dizzy from rolling over in his grave.

Are the benefits of Intermittent Fasting a direct consequence of the period of fasting, or from the decrease in overall calories consumed?   According to the Wikipedia entry, recent studies have shown it is the former: fasting has its own specific benefits related to the body’s multiple biochemical adaptations to maintain homeostasis. To greatly oversimplify, the body engages in Hormesis, a process of renewal and repair.  These mechanisms are not fully understood, but they are, let’s face it, wondrous!  It never ceases to amaze me how “happy” my body is, physiologically speaking, in every particular when I am in both the “fed” and the “fasting” states.

As a weight loss tool, two specific forms of IF are commonly practiced: the alternate day or third day fast in which no food whatsoever (my version: excepting water, black coffee or plain tea) is ingested for one whole day. This is actually a 38-hour fast, from dinner one day to breakfast the day after. The other form is more moderate and has increasing currency. It is commonly referred to as the 8/16 hour fast in which all food in a 24-hour period is consumed within an 8-hour window. One such example is described in The Nutrition Debate #83 here. For an office worker, this could be done by skipping breakfast (except for black coffee), eating a light meal in mid-morning break (10:30AM), a light lunch at 12:30 (hungry?!) and dinner at home at 6:30PM, all within the 8-hour window, and then you begin the 16-hour fast.

I have a favorite 3rd version of Intermittent Fast that I would like to popularize; I call it “The 23-hour IF Diet.” I start with a cup of coffee with heavy cream or ghee. There is nourishment here (I just never developed a taste for black coffee or plain tea), so this beverage is the beginning of my 1-hour eating window. Then, when my spouse arises and prepares breakfast, I eat 2 strips of bacon and 2 fried eggs. On weekends it might be “hold the bacon and substitute 3 eggs scrambled, with a little cream and/or shredded cheese, or smoked salmon tidbits, mixed in. This is a variation of my “1-2-3 Diet” described in #90 here. Then, after this 1-hour long breakfast, I fast for the next 23. No lunch, no dinner, no snacks. Drink a little water if you’re thirsty, but if you’re not, don’t. Do what your body tells you. (You won’t be hungry.)
I created “The 23-hour IF Diet” spontaneously a while back to deal with weight creep. I did it for two days in a row – just breakfast, nothing else for two days. First, I was not hungry. I was already in a fat-burning state, a mild level of ketosis. So, there was no glycogen in storage, and I was not running on “sugar” (carbohydrates, which almost all become glucose in the blood). It worked. I lost 5 pound in the first day, 7 total by the 2nd day, and 9 total in five days. As I say, it worked.


  1. Great column, Dan! I agree that IF can provide a lot of the same benefits of severe calorie restriction without the adverse effects. It works great with LCHF but it would probably be much more difficult on a low-fat diet. Sounds like your 23-hr fast has been very helpful for you. Once in a while I do the 8/16 thing, although I eat breakfast and lunch and skip dinner. It upsets me that that most people with diabetes or weight problems are told to eat small, frequent meals all day long. Constant snacking isn't necessary for anyone and will only exacerbate DM and obesity.

    1. Thanks, Franziska. There are so many ways to 'skin' the IF cat. There is an argument to be made for mixing it up (doing it in different ways), in an attempt to 'fool' the countermeasures the body employs that slow down the metabolism when there is a paucity of food.

      I also agree with your comment about the advice people are given about many small meals. Remember, though, that advice is being given to people who eat a balanced diet, i.e., those who are 'sugar burners' and need to constantly pump up their blood glucose to prevent the roller coaster effect of peaks and crashes. It's horrible advice for people who are attempting to 'regulate' AND LOWER their blood sugar, isn't it?