Mar 26, 2017

Intermittent Fasting: What I do and why

I have been fasting for 13 years. But what, exactly, does that mean? “Intermittent fasting” encompasses a range of related practices. I am often asked what exactly I do, and why.

Let me tell you.

My fasts have evolved a little over time, but my basic practice has remained the same: three one-day fasts each week.  For the last few years, this has meant Tuesday, Thursday and Saturday. I’m flexible (for example, if I’m meeting friends for lunch on Saturday, I’ll fast on Sunday instead).

Fasting means no calories between dinner one night and dinner the next night (with minor exceptions, detailed below). The fasting period is typically about 23 hours, but I don’t pay attention to precise timing. I eat dinner at the time I would normally eat based on other considerations. There’s a lot of variation (from 19 to 28 hours).

What are the exceptions to my complete fast? First, I typically have a glass of wine after dinner. Whether that’s an exception during the fast or an extension of dinner (meaning that the fast starts later) is a matter of definition; I think of it as an exception. I also take daily vitamins at bedtime, and a small amount (about 5-10 mls., or a teaspoon) of cod liver oil first thing in the morning. I also drink lots of water and black coffee, but don’t consider that an exception, since there are no calories or macronutrients involved. That’s it!

This is a more complete fast than recommended by Krista Varady (in “The Every Other Day Diet”) or Michael Mosley (the 5:2 diet). It’s also more strict than when I started out. For many years, I would have a latte in the afternoon on fast days, but I’ve stopped doing that. I would recommend that beginners eat 200 to 500 calories during the fasting period, at least until they become comfortable with fasting, but I like the simplicity of a complete fast.

So, that’s how I fast. What I do on eating days is not, technically, part of intermittent fasting, and I don’t follow any strict rules, but I’ll tell you anyway. I try to follow a healthy diet. To be consistent with the science behind my reasons for fasting, which are very much about reducing insulin signaling, I avoid anything that will cause a spike in blood sugar. That includes sugar and most starches. People differ considerably in their glycemic response to different foods (Zeevi et al. 2015), so I measure my blood sugar after meals (and snacks), and avoid foods that cause a spike. I hope to write another post about my findings later. If you want to follow my example without going to the trouble of measuring your blood glucose after meals, avoid foods that are reported to have a high glycemic index, and choose unprocessed foods that are high in fiber.

Recently, I’ve started making it a point to have breakfast on non-fast days, and I never eat after dinner, whether it’s a fast day or not. I eat lots of vegetables (broccoli, cauliflower, brussel sprouts, Chinese broccoli, squash), and usually start dinner with a salad, dressed with oil and vinegar. I can’t claim to eat a low carb diet, but I’m definitely eating many fewer carbohydrates than a typical American. I eat a lot of nuts and cheese, and choose fish or chicken over red meat. My favorite desserts (flan, shortbread, ice cream, dark chocolates) have added sugar, but I never eat foods with gratuitous sugar (for example, sweetened drinks or yogurt), and prefer plain versions (e.g. seltzer or plain yogurt).

That’s what I mean by intermittent fasting. It’s a healthy and simple lifestyle. I recommend it.