Friday, November 27, 2009

In Defense Of: Alternate-Day Fasting

I decided I'd better not put this one off. The concept of going an entire day without eating is likely to scare some concerned friends, family, co-workers, etc. Looks like I've got some informing to do.

Here's a quick sample of the studies that "alternate day fasting" brings up on Google Scholar:

Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism

And a summary, so you don't have to:

Subjects lost 2.5 ± 0.5% of their initial body weight (P < 0.001) and 4 ± 1% of their initial fat mass (P < 0.001). Hunger increased on the first day of fasting and remained elevated (P < 0.001). RMR and RQ did not change significantly from baseline to day 21, but RQ decreased on day 22 (P < 0.001), which resulted in an average daily increase in fat oxidation of ≥15 g. Glucose and ghrelin did not change significantly from baseline with alternate-day fasting, whereas fasting insulin decreased 57 ± 4% (P < 0.001).

Hot damn. This was done over a period of 22 days. Twenty. Two. Days. And subjects lost 2.5% of their body weight! What's more, we're NOT looking at muscle loss here! Increase in fat oxidation means more fat is getting converted to ATP. ATP is "the main energy source of cellular functions." Side note, this is a great argument for the use of fat (not carbohydrate) as the primary dietary energy source. How bout some math?

Let's assume I weigh 170 pounds (I do). Let's assume I'm going to be doing ADF for 22 days (I will). Let's assume I get the same results (not likely, but for the math's sake, it will help you visualize the results).

170 * .025 = 4.25 pounds lost.
Now, let's assume I'm about 20% body fat (I don't actually know mine).

170 * .2 = 34 pounds of bodyfat
34 * .04 = 1.36 pounds of bodyfat lost.
Now, intitally that doesn't look great. That means of the 4.25lbs lost, only 32% of that was bodyfat. The rest was likely muscle (and some water). But lest you think I'm making an argument against my own method, let me point out something very important about this study:

The full study states that subjects were asked to avoid exercise before visiting to be tested (2 days before the experiment, and 1 after). It also states that of the 16 participants, 7 were considered sedentary. As I've said before (and will Defend very soon), proper exercise stimulates release of hGH and testosterone, both of which are responsible for the mobilization of free fatty acids. The study also says nothing about what the subjects ate on 'feast' days. High levels of carbohydrate could mean higher fasted glucose levels. I hypothesize that combining the P/P lifestyle with ADF will increase the benefits of both.

How bout another?

Alternate-day fasting and chronic disease prevention: a review of human and animal trials

The summary:

A large body of evidence for the physiologic benefits and life-extending properties of CR now exists. Restricting daily energy intake by 15– 40% has been shown in both animals and humans to improve glucose tolerance and insulin action, which indicates an enhancement in insulin sensitivity (7, 8); to reduce blood pressure and the heart rate, which is consistent with ben- efits for cardiovascular health (9–11); and to reduce oxidative damage to lipids, protein, and DNA, which implies a protective effect against oxidative stress (12–15). Many other effects of CR have been documented, including increased average and maxi- mal life span (12), reduced incidence of spontaneous and induced cancers (13), resistance of neurons to degeneration (14), lower rates of kidney disease (15), and prolongation of reproductive function (16). 
Just what I like: Loads upon loads of citations. The full text is here for anyone interested.

Before anyone gets on me, yes, CR is caloric restriction. This paragraph isn't talking specifically about ADF, however, recall that my plan will create a 2000-calorie deficit. Therefore, in my case, my ADF diet is also a CR diet.

Enhanced insulin sensitivity means less insulin to do the same amount of work. This is a good thing. Insulin's primary role is to metabolize glucose (a byproduct of carbohydrate consumption). If the body needs less of it, we also get less of insulin's negative effects (namely fat storage) and decrease demand from the pancreas for production.

Oxidative stress is an underlying cause of artherosclerosis, one of the pesky diseases that cholesterol gets blamed for. These studies suggest that CR actually has an antioxidant effect.

Reductions in blood sugar, heart rate, and incidence of cancers are self-explanatory.

Prolongation of reproductive production I primarily highlighted for fun. Men, this means caloric restriction could prevent you from needing Viagra and Levitra. Are you sold on it yet?

Resistance of neurons to degeneration? We're talking resistance to Alzheimer's and dementia, here. And this is strictly from eating less, not even eating correctly!

"Let food be thy medicine and medicine be thy food."
Yup. Sounds about right. There are more studies out here, but I'll let you wrap your heads around these for now. I think these back up my point enough.


  1. It is good to control insulin! You always need a little insulin, but very little. Many reasons to keep insulin Low, low,low....

    You considering a longer 3-5-7 day fast in the plan at some point?

  2. I personally believe that, under normal circumstances, the body won't produce insulin levels that are too low. The lower, the better, I think.

    Not going to consider a longer one at this point. Want to see if there's more research on longer fasts, as well as ease into this routine first.

  3. My only thoughts right now are, as you mentioned, it would be great to combine a bunch of methods to actually find out your body fat percentage, and of course to realize that it will change even more so with additional muscle.

    But also, I simply don't have much use for studies. People in every camp (low fat, low carb, paleo, vegan, etc) will pick apart and bash studies that don't support their position, and then turn around and praise studies that do support their position. I just don't have much use for them. I know what's worked for me, and while it's not entirely scientific, looking at our evolutionary heritage is enough for me to figure that it's probably right. I mean, would we stick a bear in Nike's, on a treadmill for hours, feeding it fat-free yogurt with granola and call it it's natural way of living? No, and that certainly applies to us as well.

    I think another reason I don't really care for studies is that we tend to wave them around as proof of our positions, like we have to convince those of us in our lives that our way of eating and moving is somehow justified. Fuck'em I say! I've given up trying to persuade, and I know what works for me. And if I ever actually follow through with what works for me (slave to biology!), and even the proof of my own health and fitness isn't enough for them, then who cares, really, about proving my point.