Since August, I've been playing around with intermittent fasting (IF). This might sound bizarre to some of you, but as the Drs. Eades have pointed out, IF has been shown to have a number of benefits, including:
- Improving longevity;
- Reducing the risk of cancer and other diseases (ranging from heart disease to Parkinson's and Alzheimer's); and
- Improving insulin sensitivity and blood glucose regulation.
During fasting, almost every system in the body is "turned down," [U.C. Berkeley endocrinology professor Mark] Hellerstein says. The body changes how it uses fuel. Certain hormone levels fall. Growth stops. Reproduction becomes impossible. "By the end of three weeks of fasting you are a completely different metabolic creature," he says. "It affects many, many processes -- but in a somewhat predictable way that takes you toward disease prevention."Oddly enough, scientists don't yet know why IF produces these health benefits.
One theory is that the process produces just enough stress in cells to be good. "What our evidence suggests is that nerve cells in animals that are on dietary energy restriction are under mild stress," [Mark] Mattson [of the National Institute on Aging] says. "It's a mild stress that stimulates the production of proteins that protect the neurons against more severe stress."But whatever the reasons, IF seems to work. And it has other practical benefits, too, like:
- Increasing growth hormone during fasting (which helps build and maintain muscle mass);
- Weight and body composition maintenance; and
- Not having to make breakfast.
Let's review: A consistent line of research (going all the way back to the 1940s) demonstrates that IF confer lots of health benefits. And science has also disproven the theory that constantly grazing on tiny portions of food throughout the day somehow improves health.
You know me: Based on what I'd learned, I had to give IF a try.
More after the jump...
First, I had to pick a flavor of IF. There are numerous and varied IF approaches out there: Some involve fasting every other day (a.k.a., alternate day fasting), fasting for 24 hours a couple times a week (like Brad Pilon's Eat Stop Eat), or fasting in an ad hoc, unstructured way (like how Richard Nikoley does it). Others allow for daily eating, but only during certain windows, like Ori Hofmekler's The Warrior Diet, which calls for an "under-eating" phase of 20+ hours followed by a freakishly large meal.
After shopping around, I decided to try Martin Berkhan's Leangains approach to IF. Here's how Berkhan describes his protocol:
In a nutshell, I fast 16 hours and feed 8 hours every day. Those hours are centered around the workout, strategically placed so that a great majority of the calories are ingested in the post-workout window. Specifically, I break the fast with a meal about 2 hours pre-workout, train, and eat the rest of the calorie allotment for the day, split into two meals post-workout. One of the main differences between my diet and other fasting based diets is the importance placed on pre- and post-workout nutrition, which I think is vital to optimize results and amplify the anabolic stimulus provided by training.(Since I work out at 5 a.m., and don't eat until lunchtime, I actually follow Berkhan's modified approach for fasting early morning exercisers. You can read about it here.)
But what about muscle loss during intermittent fasting? While muscle catabolism isn't an issue with IF generally -- even with 24+ hour fasts -- the 16 hours of daily Leangains fasting certainly alleviates any fears that muscle loss will occur in such a short window of time. As Berkhan writes:
[S]tudies on this topic show that genes controlling muscle catabolism, do not even get activated with 40 hours of fasting -- and we’re only fasting for 16 hours. Here’s what the researchers wrote:
"...short-term fasting (40 h) fails to elicit marked alteration of the genes regulating both muscle- specific protein synthesis or atrophy. Greater periods of fasting may be required to initiate coordinated inhibition of myogenic and atrogenic gene expression"
"...it is likely 40 h would be insufficient time to stimulate marked catabolic processes and subsequent atrophy within skeletal muscle." (Larsen et al., 2006)
- Skip breakfast, and
- Stop eating after dinner.
Surprisingly, I don't get hungry when I'm fasting. It helps that I'm asleep for half of the 16 hours I'm fasting, but even after a hard morning workout, I'm not famished. Avoiding unnecessary carbs and eating paleo have something to do with it, I'm sure. I just don't get cravings for cereal or muffins anymore.
(That doesn't mean I don't lick my chops over the prospect of some solid, meaty breakfast-y fare, though. A few weeks ago, I tore into the English breakfast at The Breslin -- but not until after 11:30 a.m.)
Even when 11:30 rolls around and my "feeding window" has begun, I often find that I'm not hungry yet. There are days when I'll be immersed in something (work, usually) and forget to eat until I finally look up at the clock and realize it's after noon.
Another thing: During my eight-hour "feeding window" (from 11:30 a.m. to 7:30 p.m.), I'm perfectly full. I eat to satiety, but I don't feel the need to overdo it by cramming anything and everything into my mouth. I don't weigh and measure my food, but I probably end up eating somewhat less than I did before I began experimenting with IF.
And from a performance standpoint? It's all good: I'm still making solid gains at CrossFit, and I'm steadily gaining muscle mass while keeping my body fat percentage around 10 percent.
So until I learn that IF is actually horrible for me, you won't find me making a midnight trip to the fridge for a snack.
(Note: Your mileage may vary, though -- M has been IF'ing, too, but only for 12 hours each day, after which she gets desperate for food. From an evolutionary perspective, it's possible that men may be more cut out for IF than women.)
