March 20, 2019 by Dr. Kyle Varner in Intermittent Fasting

‘My diet starts tomorrow.’

Everyone and their dog has said that to themselves before.

For years, when I was obese, those words popped in my head right before I’d binge on more carbs and sugary junk than you can imagine.

The next morning, I’d feel even worse than the garbage I stuffed myself with the night before, so I’d vow not to eat a thing for the next 24 hours.

Four hours later, I felt shaky, weak, and my guts felt like they were rotting. I had to eat something—cue the carbs.

And so the cycle continued…

So you can see why I was skeptical about intermittent fasting (IF) when I first heard about it. I tried ‘fasting’ time and time again and ended up at 300 pounds.

But curiosity kicked in and I decided to research what IF was all about.

Turns out the sugary junk I stuffed myself with the nights before in the past had set me up for failure.

The right way to prepare for a fast isn’t just about how much you eat, but also what type of food you eat.

Want to know more? Read on to find out…

How much food should you eat before a fast

Preparing for a fast is extremely important. Contrary to what you might think, it’s not actually wise to fill yourself before a fast to the point you feel you might explode.

Sure, everybody’s different, but if anything, you should wind down your food intake before you finally stop eating.

The reason? Two words: stomach distensibility.

Your body is in a never-ending cycle of feedback loops, and the size of your stomach is no exception. If you eat lots, your stomach will expand to accommodate it. If you eat little, it shrinks.

And a small stomach doesn’t invite as much hunger as an expanded one.  

This will help you with intermittent fasting and especially if you plan to fast for a couple of days or more. Longer fasts require more preparation because you’ll need to manage your hunger for a longer stretch of time.

This is incredibly important, as food cravings are the number one reason people fail on a fast.

In fact, I’m in the middle of a 21-day fast, and I can tell you it helped me a lot.

What to eat before starting a fast for weight loss

This will come as no surprise to regular readers, but the answer is fat.

I’m a big fan of both keto (a fat-based diet) and intermittent fasting. They’re both wonderful for health and weight loss, but it’s the icing on the (low-carb) cake that they complement each other too!

There are two main reasons for fats when it comes to fasting preparation: weight loss and health benefits.

For weight loss, fat is useful as it ‘primes the pump’ for ketosis. What I mean by that is when you’re fasted, your body wants to find an alternate energy source. You’ll go into ketosis, and start using fat for energy instead of sugar.

So why not make it easier on yourself? If you consume more fats instead of carbs before you fast, you make your body more used to utilizing fats. This will make the initial discomfort much easier, as you’ll shorten the transition period.

The second reason why fats are good for weight loss has to do with the stomach distensibility I mentioned earlier. Fats are very calorie-dense: for every gram of fat, you get far more calories than carbs or protein.

This means you can have more energy in your body before you fast without a bigger stomach!

What to eat before starting a fast for health

If you fast for health reasons, the story is similar, but for slightly different reasons.

One of the most notable health benefits of fasting is autophagy, where your stronger cells eat weaker or dying cells for energy. This makes you feel rejuvenated and stronger.

There are two types of fats which make this process much easier: medium-chain triglycerides (MCT) and docosahexaenoic acid (DHA).

You can find MCT in things like coconut and palm kernel oil, while DHA is in fish like anchovies, salmon, mackerel and sardines. You can also find DHA in some algae sources.

You may know DHA as omega-3, something we all know as super healthy. You can take both of these in supplement form, but I’d recommend your last meal contains lots of MCT and omega-3.

If you’re not concerned about these brilliant health benefits or weight loss, and just like the feeling of being fasted, it is still possible to eat carbs beforehand.

If you’re going to do this, I also highly recommend eating a lot of fiber with your last meal. This will slow down the digestion process and give your carbs more bang for their buck.

Psyllium husk is a great source of pure fiber for this.

General tips for eating before a fast

The number one rule for fasting is obvious: you don’t consume any calories. This is why you should take any supplements that contain fat, like fish oil pills, before you start your fast.

But is there anything you can eat while you’re fasted? Absolutely, and you need to.

The key is to consume things with low-to-zero calories. A more vigorous fast won’t contain any calories, but if this is your first fast it’s permissible to have a few.

Bone broth is my go-to meal for fasting, because it’s highly nutritious, and it keeps your electrolytes up and your hunger at bay.

You can’t take in any vitamins or minerals in the form of vegetables while you fast, so if you use multivitamins and mineral supplements during your fast it’ll keep you from feeling shaky and make sure you stay healthy.

This is also true for salt. When you’re fasted, there isn’t much insulin in your body, nor are there blood sugar spikes.

When this happens, your kidneys expel a load of salt and water from your body, which lowers your electrolyte levels.

This is why you should add a fair bit of salt to your last meal. It’ll help keep your electrolytes in check, and you won’t crave salt-heavy foods. Often times, when you feel hungry, it’s just that your body is craving salt, which it associates with particular types of food.


When you embark on a fast, don’t follow the crowd and eat as much as possible beforehand. Instead, look at the facts and think about how your stomach will respond.

Fats, as always, are the best route to take. Get your body used to using fats for energy, and you’ll make life far easier for yourself. Stock up on those supplements and keep yourself healthy. I’ll share my top tips for breaking a fast soon, so keep your eyes peeled for that!

This information is intended to help readers be more informed about their health options when speaking with a professional, but it should not be used alone to diagnose, treat, prevent or cure any disease or condition. Be sure to speak to a qualified doctor before taking any action to make sure that your choices reflect your actual health situation.

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