Dear Mark: What Breaks a Fast Followup

For today’s edition of Dear Mark, I’m answering a round of questions drawn from the comment section of the “What Breaks a Fast” post. You folks had tons of follow-up questions about whether other types of foods or compounds break a fast. Does a teaspoon of honey? Does elevated insulin from BCAAs? Does coconut milk? Does pure prebiotic fiber? What about longer fasts—are they recommended? And how about unsweetened cocoa powder? What explains my ability to predict your questions? Do sausages break a fast? Does liquor? How should you exercise?

Let’s dig right in:

Hey, what about honey? 1 tsp in morning tea?

A teaspoon or less of honey is fine and won’t negate the benefits of fasting. I alternate between doing collagen coffee and coffee with cream and teaspoon of sugar (which was my typical morning coffee for over a decade). No reasonable person should fear a teaspoon of sugar or honey.

For what it’s worth, honey isn’t “just” sugar. It elicits a more beneficial (or less negative) metabolic response than other forms of sugar.

I’m shocked about the BCAA. I used to fast and take BCAA’s (yes, to continue dynamic exercise). I used to find it extremely difficult to fast compared to now when I fast without taking them. Does that mean that the insulin response made fastic more difficult?

It’s possible. Insulin impairs lipolysis—the release of stored body fat into circulation for energy usage—and the success of fasting depends on lipolysis. Without lipolysis, you can’t access all that stored energy.

Thank you very much for this info!! I am a butter-coffee-for-breakfast drinker, and I always worry about the ingredients breaking a fast. Could you please comment on coconut milk (in the can)? I love putting that in my coffee/breakfast.
Thanks.

Coconut milk is a less concentrated source of medium chain triglycerides, or MCTs (as in MCT oil). MCTs convert directly to ketones, making MCT oil and to a lesser extent coconut oil or coconut milk a potential “boost” for fasting. Still, energy is energy, and any energy you take in is energy you won’t be pulling from your body.

I find MCTs and coconut to be more useful when someone is just getting the hang of fasting or ketosis—as a nice boost to get things moving in the right direction.

Keep your coconut milk under a tablespoon and you’ll be fine.

Does prebiotic (resistant starch) fiber break a fast? Acacia senegal or potato starch? Thanks!

No. If you’re worried, test your postprandial blood sugar after eating the fiber.

Great input Mark as someone 3days into a 7day water fast with electrolytes of course what’s your view on longer fasts.

Check out the post I wrote on long fasts. Potentially beneficial but the risks accumulate the longer you go. You just have to be even more careful and methodical.

How about unsweetened cocoa?

A tablespoon runs just over 12 calories (depending on the brand; some cocoa powders contain more fat and thus more calories), with around a gram of net carbs and a gram of fat. Also a nice source of potassium and magnesium, along with a ton of polyphenols which can have fasting-mimicking effects on their own.

Eating enough unsweetened cocoa powder to knock you out of your fast would be incredibly repulsive. Probably impossible.

Cocoa is definitely a nice addition.

Okay it’s almost creepy the way Sisson answers my questions before I even ask them! I was wondering about this yesterday and then this post popped up in my inbox.

How does he do that…? 

Kraft-Heinz has a strong relationship with Google and Amazon, and the Kraft acquisition gave me access to Alexa/Google Home datasets and the ability to predict what my readers are wondering about.

Just kidding, though it’s scarily not out of the realm of possibility anymore.

What about a small snack of paleo sausages, smoked or dried? So meat and fat (beef, pork or lamb), and some spices. Maybe 100g worth.

Well, that’s a legit snack bordering on a small meal. That will break the fast, but it’s not all for naught. There is the whole “fasting-mimicking diet,” where you eating very few calories for several days out of the week and retain many if not most of the benefits of full-on fasting.

Let’s just say if you ate a small snack of paleo sausages on your “fasting” days, you’d still be way ahead of 99% of people.

But do try a full-on fast at least once. You might surprise yourself.

Great post! What about alcohol? Specifically, a shot or 2 of liquor. I would assume beer and wine would break a fast, but what about whiskey or tequila?

When alcohol enters the system, utilization of all other energy sources is suspended until the alcohol is burned. Back in 1999, researchers did a study where they gave fasting adult men the equivalent of a couple shots of liquor. They stopped releasing stored body fat, stopped burning body fat, and began burning way more acetate (a product of ethanol metabolism). They didn’t exactly “break” the fast, but all the metabolic trajectories we love about fasting took a big pause.

Good morning Mark,
How does one exercise in the morning while fasting? When to eat?

You can exercise any way you like, but I change how I train based on when I’m going to break the fast with food.

If I’m going to break the fast with a meal right after, I train any way I like. I’ll do sprints, HIIT, weights, anything.

If I’m going to keep fasting after the workout, I like to stick to strength training and low-intensity movement (walking, hiking, standup paddling). The strength training is essential during a fast because it’s an anabolic signal to your muscles—move it or lose it. Simply lifting heavy things during a fast can stave off muscle loss.

That’s it for today, folks. Stay tuned later this week for “What Breaks a Fast: Supplements Edition.”

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