By Greg Perkins
The day before Thanksgiving, Tammy and I tried fasting for the first time! And we didn't die. (Though I'm pretty sure we would have died if we had tried it a few months ago, before mending our high-carb ways.)
I'd been hearing murmurs about potential benefits of occasional fasting (and more so now that I'm paying attention to some of the blogs and other resources that folks have been pointing out here on Noodlefood). Like the general concept of shaking up the system to keep it on its genetic toes, using the energy stored in body fat, boosting muscle production, strengthening the immune system, helping on the longevity front, etc.
Anyway, after hearing some random news report say that the average American doubles their already-huge caloric intake on Thanksgiving, we thought we'd just skip food the day before and call it even. (Yes, I kid.)
I don't normally eat breakfast (I'm a late-dinner kind of guy), so I didn't notice anything until after lunch. At that point, my system felt like it was idly wondering, "hey, where's the usual food?" But since I haven't been running on carbs for a couple months now, there was no crash and it was no big deal. I just moved on with the day and ended up back home around dinnertime. Now that's when things got tough -- not because we felt like we were starving, but because we apparently have some way-heavily-ingrained habits of enjoying nice beverages and eating and snacking the night away. We found ourselves super-fidgety and unfocused, not knowing what to do! We couldn't even break out a glass of wine or cup of coffee or a diet soda (those might undo keeping our systems level, and we wanted to experience the full effect). Sigh. Maybe that's the form in which we experience hunger now. Anyway, there was finally a recognizable symptom: our stomachs growled at us for maybe a half hour mid-evening, then gave up in disgust. We went to bed a early to try to escape the fidgety torture of not being able to pour a glass of wine and munch on almonds.
Another little surprise: we expected to be ravenous waking up on Thanksgiving, but we weren't at all -- it felt like just another morning! I was approaching 37 hours on just water, and Tammy was approaching 24 hours, not having gotten the spontaneous memo in time. Since I didn't want to even flirt with going beyond fasting and into starvation-mode, we made big omelets and savored some decked-out coffee. Then we proceeded to have two more Thanksgiving meals with our various families. And then we followed it up with late-night leftover Thanksgiving munches. Ahhhh, gluttony. :^)
Before jumping in, I looked around to try to get a better picture of whether this was a sensible idea and what to expect. Over at Mark's Daily Apple I found this little article: Is Intermittent Fasting Healthy?
Numerous animal and human studies done over the past 15 years suggest that periodic fasting can have dramatic results not only in areas of weight (fat) loss, but in overall health and longevity as well. A recent article in the American Journal of Clinical Nutrition gives a great overview of these benefits which include decreases in blood pressure, reduction in oxidative damage to lipids, protein and DNA, improvement in insulin sensitivity and glucose uptake, as well as decreases in fat mass. ... Intermittent fasting has also been shown to reduce spontaneous cancers in animal studies , which could be due to a decrease in oxidative damage or an increase in immune response.And over at Modern Forager, I found a nice series exploring What Happens To Your Body When You Fast?
One thing that is most interesting about the intermittent fasting studies is that slightly overeating on the non-fasting days (to make up for the lack of calories on fast days) yielded similar results, so it wasn’t so much about total calories as it was about the episodic deprivation.
- Liver glycogen levels are depleted within 8-10 hours. Muscle glycogen falls by 50% over 24-hours, even without exercise.
- After depleting glycogen, amino acids are recycled to be broken down for glycogen through gluconeogenesis.
- We see increases in three of the four hormones driving lipolysis, indicating a propensity towards fat burning. Somewhere around 12-18 hours, lipolysis becomes a major energy pathway, producing energy from body fat.
- T3 levels fall slightly, indicating a slightly lower metabolic rate. Urinary nitrogen excretion falls, indicating less catabolism of muscle proteins.
- Beta-hydroxy butyrate, hGH, and IGF all increase. Proteins that protect cells from stress also increase.
- Inflammatory markers decrease. Insulin sensitivity improves. AGEs likely decrease.
- Cancer protection increases, healthy cells are better protected from chemotherapy, and markers of heart disease decrease. General immunity seems to improve.
- Brain neurons are protected from stressors, BDNF increases (helps grow brain neurons), and the brain is better protected from Alzheimer’s and Parkinson’s Diseases. Fasting after a brain injury lessens the damage of the injury.
- Exercise during a fast shows a higher rate of fat burning for fuel.
- Learning is enhanced and jet lag may be reduced.
If you have any good resources to share, please post them in the comments!