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.


Unknown said...

Hi Dr. Mount,

My name is Berlin Mendez and I am a grad-student at the University of Iowa. I know you conduct research regarding splice sites in RNA, but have you ever thought of conducting research in this matter of short-term fasting?
I have struggled with obesity since my early teens, but have had very healthy levels of everything and no impediments when it came to physical activity. Recently I developed hypothyroidism, which made me gain 100 lbs in less than 2 months. Now, I have been told i am also a borderline type 2 diabetic. I followed the diets plans given to me for 2 months and not a single pound was lost and my triglycerides and glucose levels remained the same. I followed the Paleo diet and a strict crossfit program (which is so intense. My thin healthy friends threw up and passed out during it.) for a month. I only lost 2 pounds and everything else remained the same. I became increasingly frustrated and decided to fast for 2 days to see if it was possible at all for me to lose weight. I had avoided fasting, because I have a long history of anorexia and over-exercising, but I went for it anyway.
After the two days, I lost 8 pounds! I was very happy and relieved to know that there was something that could work. I did however dealt with horrible headaches during those 48 hrs.
Today I found out about you, your story and the research behind it. It sounds very promising for me and it gives me motivation to try it out. Out of everything I have tried, fasting is the only thing that seems to work well for me. I'll follow everything you described and hope it works.
I am not used to having to live with this much body mass. It's a giant impediment. And the hypothyroidism and diabetes 2 (which I would argue is pre-diabetes) don't make it any easier. I was just "permanently deferred" from donating plasma, because of it. It made me feel ashamed, defeated, and frustrated.

Thanks for sharing your experiences and I can obtain similar results to yours,
Berlin Mendez

The Info Road said...

Great blog on intermittent fasting.I just started, and am tracking progress. Watch my YouTube video at:

Jean | said...

Steve, thanks for tweeting me the link to this post. It's so interesting all the different ways people are practicing IF. I'm so completely happy with 16/8 that I'm sure I'll be doing it from now on.