How to break an intermittent fast the healthy way

From the desk of
Robb Wolf
ScienceHow to break an intermittent fast the healthy way

Hey Robb, how should I break my fast?

I get some form of this question a lot from folks in The Healthy Rebellion community. My answer depends on a few factors, but mostly on the length of the fast.

If we’re talking about intermittent fasting (also called time-restricted feeding), I just tell people to eat normally. A 12, 16, or even 24-hour fast doesn’t require a specific re-feeding strategy.

This doesn’t mean food quality doesn’t matter while intermittent fasting. You should still eat nutrient-dense whole foods (like a paleo or keto template) during feeding windows.

But you don’t need a game plan to break a short fast. You can wing it.

With longer fasts, however, you want to ease back into eating. Your digestive system goes cold during an extended fast. If you don’t handle it with kid gloves, it will protest.

I should stop here to mention that I generally recommend people get medical supervision for fasts over 36 hours. (At least for the first go-around.) This is especially necessary for type 2 diabetics who need guidance with blood sugar meds.

Another caveat—I’m not convinced that extended fasting is healthy for everyone. It has interesting therapeutic properties, but it can be a stressful and draining experience. I’m in the minority on this. While folks make much noise about mTOR, IGF-1 and similar growth factors, I think we will look back and realize that somehow we applied the fix for chronic overeating (like fasting, calorie restriction) to healthy, reasonable eating.

The occasional extended fast may be beneficial. But fasting most of the time? I doubt it. I see a lot of people struggling on BS programs that encourage frequent extended fasts.

Caveats aside, I wrote this article as a resource on how to break a fast. I hope you find it useful.

Ancient Fasting History

Fasting is super popular now, but it’s nothing revolutionary. Our ancestors practiced fasting as a matter of course.

Picture a band of hominids living 75,000 years ago. They hunted and gathered. They foraged for food. They lived off the land.

But the land didn’t always provide. It wasn’t dotted with supermarkets, restaurants, and mini markets. Because of this, our forebears often had to forgo food for days and weeks on end.

They were sustained by a backup energy system called ketosis. This allowed them to access stored body fat during a fast, fueling their brains and bodies with clean, efficient energy.

Then they would break the fast and put on enough fat to fuel their next period of scarcity. But before talking about breaking a fast, we need to get some definitions straight.

Intermittent Fasting vs. Extended Fasting

Loosely speaking, any fast between 12 and 36 hours can be considered an intermittent fast, while any fast over 36 hours can be considered an extended fast. There’s no scientific consensus on these definitions, but they provide useful benchmarks.

Some forms of intermittent fasting are practiced daily, while others are practiced weekly. Some allow limited calories on fasting days, while others don’t. For an introductory guide to intermittent fasting, check out this article I posted a while back.

Extended fasting—consuming zero calories for 36 hours or more—is a whole different animal. It should never be attempted by the unprepared.

Most of this guide is devoted to breaking a longer fast, since it complicates things. But what about a shorter fast?

How To Break an Intermittent Fast

If your fast is less than 36 hours, break it with a normal meal. The size of your re-feed, as you might imagine, will depend on your health goals.

If you’re fasting to lose weight, you’ll want to maintain a mild caloric deficit. (Around 5% fewer calories than your metabolism requires.) This often happens naturally on IF protocols, but you can also track your calories with an app like Cronometer to ensure you’re not overeating.

For instance, if you’re practicing OMAD (one meal a day), you should calibrate that meal to be slightly under your daily caloric needs. Keeping your one meal at a reasonable size also decreases the risk of indigestion.

If you’re trying to add muscle, however, OMAD isn’t an ideal protocol. You’ll want more feeding opportunities to fuel growth. You might consider something crazy, like 2 meals and a snack!

Breaking A Longer Fast

Breaking a fast over 36 hours requires planning. Why? Mostly to avoid the digestive consequences of overeating.

Even normal portions may cause trouble after a long fast. When you don’t need digestive enzymes, your body stops making them. Your pancreas may need time to resume normal production.

Unfortunately, many people act like a starving squirrel in a bathtub of cashews after a fast. Then they pay for it with indigestion, heartburn, bowel irregularities, bloating, gas, and sometimes nausea and vomiting.

Some of this overeating is driven by hunger. It’s natural and normal to feel piqued after three days without food.

But hunger tends to stabilize over time. Research has found, for instance, that a 12-hour and 36-hour fast have similar effects on ghrelin, the main hunger hormone. We don’t get hungrier and hungrier as time passes. It has a natural limit.

There’s also the problem of eating too much too quickly. Satiety hormones like leptin and cholecystokinin take 20 to 30 minutes to set in after a meal. That’s why it pays to eat slowly. Your eyes are bigger than your stomach.

Psychology is probably the main factor though. We’ve missed our food and want to celebrate its return in a big way.

When you see your best friend for the first time in a year, you want to do something special. Food isn’t exactly a best friend, but a similar principle applies.

I’ll talk about avoiding this situation soon. But first I need to cover a rare complication of extended fasting.

What Is Refeeding Syndrome?

Refeeding syndrome refers to medical complications that occur after an extended fast or period of malnourishment. These complications are driven mostly by the depletion of electrolytes.

Here’s how it works. After the fast, the body needs to rebuild. It needs to synthesize body fat, glycogen, and muscle tissue. These activities require electrolytes like phosphorus, magnesium, sodium, and potassium.

In the case of refeeding syndrome, these electrolytes have been overly-depleted by extended fasting or prolonged starvation. This causes the body to break down muscle and other important tissues to meet basic needs.

Post-fast disturbances in electrolytes like sodium, phosphorus, potassium, and magnesium can also cause weakness, fatigue, cramps, tremors, irregular heartbeat, and swelling of the extremities. In severe cases, these disturbances can cause brain damage, seizures, and death.

Fortunately, refeeding syndrome is quite rare in healthy people. The groups at higher risk include:

  • Those with anorexia nervosa
  • Underweight people
  • Alcoholics or former alcoholics
  • Those on diuretics
  • Anyone undergoing long periods of malnourishment

Extended water-only fasts also increase the risk of refeeding syndrome. This is a big reason why consuming electrolytes—through bone broth, electrolyte water, or supplementation—is essential during a fast.

Tips For Breaking an Extended Fast

You’re coming to the end of an extended fast. You’ve gone three days without food, you’re hungry, and you’re ready for a big meal.

Before you start eating, mind these tips.

#1: Be hydrated with fluids and electrolytes

We just covered a rare fasting complication called refeeding syndrome. That’s a severe electrolyte disturbance. Milder electrolyte disturbances, however, are MUCH more common in the fasting population.

During a fast, you lose more electrolytes like sodium and potassium through urine. And your dietary intake is nonexistent. It’s a formula for electrolyte imbalances that can tank your energy.

So before and after you refeed, get your fluids and electrolytes handled. This might mean sipping LMNT, drinking bone broth, or supplementing ad hoc.

#2: Start small

Don’t make your first meal back a whopper. Instead, consume a high-protein snack of 200-300 calories one hour before the true meal.

Eating a snack first gives your satiety hormones a chance to kick in. This helps prevent subsequent overeating.

Why a high-protein snack? Because protein is relatively easy to digest, plus the amino acids will stop your body from breaking down muscle. I recommend lean meats like chicken or fish.

#3: Eat agreeable foods

The post-fast period is a sensitive time for your gut. That’s why you need to avoid foods you’re sensitive to.

The most common problem foods include:

  • Gluten
  • Eggs
  • Soy
  • Nuts
  • Dairy
  • Raw vegetables
  • Alcohol

This doesn’t mean you can’t eat any of these foods. But when in doubt, play it safe.

Some sources recommend a salad as the first meal back, but I recommend cooking your vegetables instead. Cooking enhances the digestibility of most foods.

#4: Avoid alcohol

While we’re talking about problem foods, we should talk about alcohol. One glass of wine shouldn’t be a problem, but heavy drinking increases the risk for a dangerous condition called alcoholic ketoacidosis. Alcoholic ketoacidosis is most common in alcoholics and binge drinkers, but it can occur in anyone.

My advice is to avoid alcohol altogether when breaking a fast. Even small amounts of alcohol can impair digestion.

#5: Promote digestion

Here are some quick tips to improve digestion when you break your fast:

  • Chew your food slowly and mindfully.
  • Consume peeled ginger root (shown to accelerate gastric emptying).
  • Take a walk after the meal.
  • Stay upright as much as possible (gravity aids digestion).
  • Eat a forkful of fermented food like sauerkraut or kimchi with your meal.

#6: Don’t overeat

The most important rule when breaking an extended fast is to avoid gorging yourself. Think normal portions. Don’t try to replace all the calories you missed.

The best way to avoid overeating is to plan ahead. Follow tip #2 (have a snack first) and have a reasonable meal all planned out. Leave nothing to chance. That’s how you break a fast the healthy way.

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