how many calories break a fast

How Many Calories Break a Fast?

You’ve come to learn how much you can eat without breaking a fast.

Maybe you don’t like black coffee and need a little cream.

Maybe you want some sugar in your tea.

These are part of your routine and you’re new to fasting.

You want the benefits of fasting and are worried the cream or protein powder will end the fast.

It will and it won’t.

The answer really depends on your goals for the fast.

Do you want to lose weight?

Do you want to live longer?

Do you want to kick start autophagy where you break down pre-cancerous cells?

All these things and more happen when you fast correctly.

In this article will cover your goals for fasting and how much you can eat while still reaping the benefits.

how many calories break a fast

Do 100 calories break a fast? Where did the 50 calorie rule come from?

Likely this isn’t your first article on fasting. You’ve been reading about the benefits and you’re excited.

You may have also heard of the 50 calorie rule.

But where did this rule come from and is it true?

This rule is seen over and over again throughout the web.

It originally started by some of the first well-published fasters, like Martin Berkham from Lean Gains.

His form of fasting involved taking BCAAs to get some protein during fasted workouts.

A usual serving of BCAAs comes in at 45 – 50 calories.

Martin found that this small amount did not affect his fat loss and muscle gain goals.

So he said not to worry about it.

Does it end the biochemical processes involved with fasting?

Yes. You’ll leave ketosis and likely have a small insulin spike. You’ll increase mTOR and likely stop autophagy for the time being.

Does it matter regarding your goals? Not really.

How many calories break a fast?

Krista Varaday has been studying alternate day fasting for years. In the end she wrote a book on the results and how to implement it.

When I first heard of alternate day fasting it sounded horrible.

I’d fasted before and knew that it can be hard.

The thought of fasting every other day sounded like a nightmare.

So I never even read into her method.

Her method doesn’t involve total fasting though.

On eating days you eat as normal.

On fasting days you still eat 500 calories.

Does that break ketosis? Yes.

Does that stop autophagy? Yes.

Does that spike insulin and mTOR? Yes.

Will you still lose weight? Absolutely, and tons of it.

How Aren’t There Fasts Where You Eat on Fasting Days? 

The popular 5:2 fast that you may have seen in books or on the BBC special is also based on this type of fasting. Instead of every other day fasting you just do two fasting days where you eat 500 calories each day.

With their method you don’t even have to eat the 500 calories all in one meal.

You can spread it out over the day.

That’s an insulin spike nightmare! You’ll keep your insulin up all day doing that.

Does it stop the “fast”? Yes indeed.

Do you still lose weight even with insuling up? Absolutely.

Can you still get longevity and other benefits doing this? Yes for mice. Still waiting on more results for humans (we live longer).

How many calories can I eat and still achieve my goals?

Now we’re getting to the good stuff!

You’ve seen how eating anything stops a fast, yet you can still achieve your goals.

But how much can you eat?

In all the studies on alternate day fasting, Krista Varaday found an average of 500 calories during the fasting day was perfect.

At first she would calculate how many calories you could eat based on your height and body weight.

As expected, it varied greatly for different sized men and women.

She found when you average all the different calories counts together they all came out to 500 calories. That number was 25 calories higher than the female average (475) and 25 calories lower than the male average (525).

It still worked though. She changed the studies and had everyone eating 500 calories on their fasted days and they still achieved the benefits, regardless of their height.

Will eating stop fat loss?

Yes, but only for a limited time.

And now, it’s time for some math.

Don’t worry, I’ll keep it fun.

This isn’t an article on fat loss but we need to spend a little time talking about fasting and fat.

You see, your body is constantly using both carbs and fats for energy.

If you’re running or doing aerobic exercise your body will prefer carb energy over fat energy because it has faster access to carb energy.

Fat energy takes longer to break down.

Still, you are always burning fat.

If you fast for 16 hours you’ll consume most of the stored carbs (via glycogen) in your muscles and liver. After that you start burning more and more fat until you enter that glorious state everyone raves about, ketosis.

But ketosis isn’t needed.

Your body is always burning fat.

Even while you’re watching TV, about 60-70% of the calories you burn will be from fat stores. The other 30-40% comes from glycogen and sugar.

Now For the Calorie Math

In general most people burn about 1 calorie per minute.

That comes from the following:

160 lb person burns approximate 2000 calories per day.

Of that 2,000 calories, about 1,500 of that is just your base metabolism, what you need to stay alive in a coma. The other 500 or so comes from walking, washing dishes, showering, and basic living and moving.

There are 24 hours in a day, or about 1,440 minutes per day.

I’m guessing you can see where this math is going.

1,500 calories divided by 1,440 minutes is approximately 1 calorie burned per minute.

If you’re just sitting watching TV let’s assume on the low end you’re burning 60% of that calorie from your fat stores.

In an hour you burn 60 calories total, and 36 of those come from fat.

Given 3500 calories per pound of fat, it will take you about 97 hours of binge watching Netflix to burn a pound of flab.

Most people watch 5 hours of TV a day. That’s about a pound of fat lost for every 2.5 weeks of TV watching.

So how does burning fat watching TV relate to calories to break a fast?

So this is how you get to your own rule of 50 calories to break a fast.

You saw in the previous section that you burn 60 calories per hour just sitting around. Of that 36 calories is fat.

So, if you eat 50 calories of cream in your coffee during a fast you’ll pause fat burning for about an hour and a half.

So instead of a rule saying no more than 50 calories, think of it as hours lost.

For every 36 calories you eat, you’ll pause fat burning for 1 hour.

So now you have the tool to decide, is that cream in my coffee worth pausing fat burning for an hour? It still takes 97 hours to burn off a whole pound of fat while watching TV.

One hour is just a drop in the bucket. If that 36 calories in your coffee while binging on Netflix prevents you from eating a bag of chips it’s more than worth it.

Does coffee break a fast?

Yes and no. According to Dr. Satchin Panda, who studies time-restriced feeding (eating in 8 hour windows during the day), anything you ingest breaks a fast.

Does it matter for your goals? Not really.

Like we discussed above, any calories ingested just pauses fat burning. 36 calories ingested will pause passive fat burning for one hour.

Coffee comes in at 5 calories per cup drunk black. According to our calcs that will stop fat burning for about 8 minutes.

When I first discovered Dr. Satchin Panda’s research I got excited. He had mice eating high fat, high carb foods in time-restricted windows and they didn’t gain weight and had excellent heart health.

The coffee comment he made nearly made me stop fasting. I love my coffee. It gets me through the fast.

If this is the case for you keep drinking it. You won’t be dissappointed in the results.

Besides, coffee has been shown to stimulate autophagy (clearing out of dead cells in the body). Usually that takes extended fasts beyond 2 days to kick in.

Does diet soda and artificial sweeteners break a fast?

Calorie free drinks have been studied extensively. Without going into depth here, for all intensive purposes they do not break a fast.

Some artificial sugars give an insulin spike and artificial sugars are linked to higher Diabetes 2 risk.

The real danger is overeating after the fast. The sweet taste of diet soda tells your body sugar is coming. When it fails to come the body still expects it. Scientists speculate that the reason diet soda is linked to higher weight is that it causes people to overeat later.

So even though diet soda can help you get through a fast without breaking it, you may find yourself overeating later.

Don’t give up on it yet. Many, like Tim Ferris, simply limit their intake to 16 ounces of diet soda a day. He found that beyond that it would ruin his fat loss.

Do your own experiments with diet soda on yourself. Keep a journal of how much you drink during fasting and how your fat loss and weight changes during that time.

Does Fat Break Fasting?

Of the three macronutrients, fat causes the least amount of insulin spiking after eating. That’s assuming you eat pure fat.

Does it break a fast? Again we go by the calorie rule – 36 calories of anything pauses your fat burning for one hour.

Will butter in your coffee break a fast? Yes. Will it stop your weight loss? It depends on what you eat later that day. In general, those that subscribe to bulletproof coffee do well on the plan if they can keep their eating in line with that plan the rest of the day.

Me personally, I have never succeeded on plans that eliminate food groups. That’s why I fast. To balance out overeating at other times.

Eating is joy. Eat with your friends. Enjoy Christmas. And when it’s time to get back to the fast, skip the butter in your coffee.

Do BCAAs break a fast?

Following the calorie rule (36 calories pauses a fast for one hour), BCAAs will break a fast. But what’s one hour? Not much.

BCAAs come from Martin Berkham’s Lean Gains program. He got great results using BCAAs during fasting. He worked out hard though.

Do you need them to gain muscle while fasting? Maybe. Try your own experiment though. Track your strength gains and measurements for a few weeks without BCAAs. Then track again for a few weeks with BCAAs.

Which one worked better for you?

The goal of fasting is to get more results with less. Less work, less eating, less cooking, and less supplements.


Does bone broth break a fast? Veggie broth?

Dr. Jason Fung is one of the biggest proponents of using broth during fasting. Why? He doesn’t want you to have headaches and adverse effects from low sodium levels.

He also recommends full 36 hour fasts with no meals. That means skipping an entire day of eating. For instance, you eat dinner monday, skip all meals and food on Tuesday, then resume eating Wednesday for breakfast.

If you do that it may help to have some broth.

Will it stop autophagy and other benefits of fasting? Yes.

Will it stop weight loss if you’re following Fung’s plan? Absolutely not.

The goal of your fasting always gives your answer.

Why do you want to eat anything?

The hardest part of fastest is not the hunger. It’s battling your mind. Learning it’s tricks. And getting around those tricks.

Asking how many calories you can eat during fasting is one of those tricks.

You can beat it though by using the information above.

First, define your goals – weight loss, longevity, or improved health.

Then define your fast limits accordingly.

And go easy on yourself. One goal at a time.

If coffee with cream gets you through a Fung fast of 36 hours then do it.

You will lose plenty of weight beyond that cream.

Able to have diet soda without a sugar binge later? Do it.

But every now and then try a fast without consuming anything.

Humans have been fasting on purpose for spiritual reasons for thousands of years.

They didn’t have coffee. They didn’t have diet soda.

They did it to spend time with themselves without distraction.

For me, fasting is a lot easier when I add a spiritual element to it. When I know I’m getting emotional repair and spiritual benefits along with the physical, it makes the choice of coffee a non-choice.

So try a food-free fast sometime. Use it to take a pause from all the doing and get back to being.

You won’t be disappointed.