If you’re a regular listener to the CLB podcast, you’ll hear me, in our next episode (coming soon!) discussing the latest neuroscience research on intermittent energy restriction (IER). IER, as the name implies, involves intermittently restricting energy intake, or calories. You can do this in several ways. In one method you severely restrict calories (think 400-500 total intake per day) two to three days a week; in another you confine your food intake to an 8-hour period every day; and in yet another you fast once a week for a 24- to 36-hour period.
Sound intriguing? Difficult? Impossible? Read on . . .
The benefits of intermittent fasting for metabolic health are already pretty well established. In non-human animal models as well as in humans, IER leads to weight loss and reduced body fat; lowers blood pressure and resting heart rate; and improves risk markers for cancer, diabetes, and cardiovascular disease. This is true even when the faster’s overall calorie consumption is the same as a non-faster (because, for example, the faster consumes more calories during his non-fasting periods than he would otherwise). Just by giving yourself an occasional break from eating, then, you do your body a big favor, even if you don’t eat less overall.
But as described at a symposium held last November at the Society for Neuroscience’s annual meeting (a summary of which is published here), it’s becoming clear that the advantages of IER are even further reaching, with enormous implications for brain health. Human and non-human animal studies have shown that IER increases synaptic plasticity (a biological marker of learning and memory), enhances performance on memory tests in the eldery, leads to the growth of new neurons, promotes recovery after stroke or traumatic brain injury, decreases risk for neurodegenerative diseases like Alzheimer’s and Parkinson’s disease, and may improve quality of life and cognitive function for those already diagnosed with these diseases. IER has also been shown to play a preventative and therapeutic role in mood disorders like anxiety and depression.
The rewards of IER for metabolic and brain health are mediated by a number of complex biological mechanisms, but the underlying idea behind the science is simple: Periodically challenge your cells and biological systems (by food deprivation) in a controlled way, and these cells and systems will become stronger, more efficient, and better able to handle the daily stresses that come their way. It’s the same basic idea that underlies weight-training and other forms of exercise. We damage our muscles (a little bit) to build them up.
Trying at Home
Given the increasing scientific consensus and the huge potential payoff for brain and body health, I decided after recording our podcast that I had better put my money—or my empty fork— where my mouth is and give IER a try. Though the human IER studies report fasters complaining of initial side effects like grumpiness, headaches, and preoccupation with hunger, they also say that after about a month, most fasters adapt and learn to tolerate the fasting lifestyle pretty well. So, with this in mind, starting last November, I gave it a try.
The first method I attempted was the 8-on, 16-off method. For me, this meant no food beginning after dinner (about 8pm) for 16 hours. I could eat again at about noon the next day.
I tried this method for a week. I reported grumpiness, headaches, and preoccupation with hunger. The biggest problem with this method for me was that I’m a big breakfast eater. I like to wake up, work out, and eat . . . and the first two items on this list are a lot less motivating when the third isn’t there. Though I did get more used to the routine by the end of the week (I solved the headache problem by forcing myself to drink more water), the thought of going without breakfast every day made me depressed. And depression is not good for brain health.
So I decided to try the weekly 24-hour fast instead. This way, I reasoned, I could get the fasting over with in one shot. I started in late November, and have been fasting once a week, dinner-to-dinner, since. I even managed to keep it up over the holidays.
Have I adapted to my new lifestyle? Well, yes and no. I don’t get headaches, I’m usually not too grumpy on fast days, and if I keep myself busy—I always fast on weekdays— I can usually get through the day without thinking too much about food (though when 5 o’clock comes around you might catch me googling recipes and daydreaming about what I’m going to make for dinner that night). But going without food for 24 hours is just hard, and it seems like it will continue to be hard no matter how many times I do it. I did it yesterday, for the 6th or 7th time. It was hard.
Despite the difficulty, though, over time I’ve experienced an unexpected reaction to my fasting routine. I’ve come, perversely, to enjoy it. And though psychologically, I don’t necessarily look forward to my fast days, physically, I do. It’s a feeling that’s hard to explain, but if you’re a regular exerciser you might understand an analogy: it’s similar to the desire you feel to get up and get moving after being sedentary for a long period. And when I’m through with a fast, to continue the exercise analogy, I feel like I do after finishing a tough workout: spent, but happy. It’s this unexpected reaction, which, it turns out, is not unusual, that has convinced me that fasting is good for me.
So if you’re thinking about New Year’s resolutions for physical and mental health, I would recommend, based on the science and my own experience, giving IER a try. It can’t hurt if you’re smart about it, and it very likely will help you develop a stronger, healthier, body and brain. But don’t hold me responsible if, in the short term at least, grumpiness, headaches, or preoccupation with food ensue.