Photo by Charles Deluvio on Unsplash

Hey guys, let’s talk about one of the most powerful tools in the weight-loss arsenal: Fasting.

Fasting is a kick-ass weapon for improving your metabolism, lowering your cancer risk, and getting a great body if you’re a guy. If you’re a girl, it gets a little more tricky, but we’ll address that too.

For men though, fasting is consistently shown to improve metabolism, increase insulin sensitivity, aid in weight loss, etc.

When it comes to using this tool, we have a few options. Intermittent fasting lets us enter a fasted state without lowering calories. This is a common practice among men even when they don’t know it. Male guests of the Tim Ferriss Show over the age of 40 almost all skip breakfast. Considering the show is about teasing out the tools, tactics and techniques of top performers, this is an interesting trend.

Then you have the longer 24 hour fasts, and multi-day fasts. These options can be great for focusing on optimizing your metabolism, losing significant weight, or garnering the cancer prevention benefits of fasting. As you can imagine, however, they also are more taxing on the body and require more supervision and prep depending on your personal health.

Finally, we should understand the purpose of fasting. Fasting helps your body become better at burning fat for fuel. By removing all calorie sources, the only remaining energy for your body is your own body fat and muscle tissue. Fat is more calorically dense and easier to burn, so your body will start there. Fast for long periods without exercise and yes, you will catabolize muscle as well, but you’d be surprised how much body fat even a lean person has available.

We’re gonna discuss the benefits of fasting, as well as how to maximize your experience with this tool. Let’s get started.

But in order to start and be super successful, you should definitely sort out your shitty habits. HOW? Get on Op Tripod and develop the three habits that form the legs of a stable tripod by signing up here

Benefits: The Importance of Autophagy

The benefits of fasting can largely be traced to autophagy. Autophagy is the process by which your body cleans up damaged and dysfunctional cells. Fasting increases autophagy, resulting in clean-up at the cellular level.

This helps maintain muscle mass, stave off the negative effects of aging, and protect the brain via neuronal autophagy.

Animal studies further support the mental benefits of fasting. Any limited diet improves mental function, but intermittent fasting (which we’ll discuss in depth later) had the most beneficial effects with the least negative consequences.

This is just a quick overview of the studied benefits. Fasting is basically a cellular reset. It helps us get rid of the junk, and in men it also acts as a potent weight loss tool. Now for fasting strategies.

Fasting Prep: Low-Carb & Ketogenic Diets

In obese individuals, supervised fasting has been used for as long as a year to burn fat. However there can be complications. Fasting is known as a hormetic stressor, meaning it technically damages the body but results in positive changes via the body’s reaction.

If you have hormone issues, chronic disease, are very unhealthy, or are quite obese, fasting is likely to be harder on you. When I was dealing with adrenal fatigue, fasting for more than 16 hours often led to heart palpitations and fatigue.

How can you put the odds in your favor? Adapt your diet first. The ketogenic diet is also known as the fasting mimicking diet for a reason. When adhering to a ketogenic diet, your body undergoes many of the same changes as when you are fasting, but without the stress of having zero dietary calories.

Feel free to try fasting without doing keto first. Many men tolerate fasting even if they eat an otherwise high-carb diet, and intermittent fasting (the next section) tends to come naturally for those on Keto and low carb as well.

But if you are worried about jumping straight in, first lowering the carb content of your diet is a great prep step.

Action Plan: 1 month low carb, 1 month keto before fasting

Hunter Gatherer societies throughout the world consume far fewer carbs than civilized peoples. Even in the highest carb groups, hunter-gatherers only get 30% of their daily calories from carbohydrate, and many such groups consume 15% or less (including groups that eat no carbohydrate year round like the Inuit or Mongolians.)

So, let’s imitate them. For 4 weeks, lower your daily carbohydrate to less than 30% of your daily calories.

Measure this by using a food scale and an app like My Macros +. Do this for one month, and you’ll have a rough idea of how much fat, carbs, and protein to eat on a daily basis to hit certain percentages.

My only caveat: Be strict as f***. When I first tried keto, I was kicking myself. I discovered that I had been naturally eating nearly keto for years, but would sabotage it with high carbohydrate junk foods at the end of the day to satisfy my cravings.

I know, it’s boring to measure things, but trust me, what gets measured gets managed. Once you’ve been measuring your food consistently for a few weeks, you’ll have intuition on your side.

I promote high protein for the benefits to longevity and strength, so aim at 1 gram per pound, or 2.2 grams per kilogram of bodyweight for your protein intake. From there, aim to get less than 30% of your daily calories from carbohydrate, and make up the difference with healthy fats.


Fats are not created equal. In fact the rancid, oxidized PUFA vegetable oils in many of our foods drive inflammation and lower insulin sensitivity. If your dietary fat consists mainly of PUFAs, you may just be making yourself fatter.

Instead, opt for saturated fats (stable at room temperature) or the few mono-unsaturated fats available. For a quick eat-this not-that:


  • Grass-fed butter
  • Beef tallow
  • Beef suet
  • Beef fat
  • Coconut oil (extra virgin and unrefined)
  • Braggs Brand Extra Virgin Olive Oil (other brands are cut with high PUFA oils)
  • Primal Kitchen Avocado Oil (again, other brands are often cut with cheap, inflammatory oils)


  • Sunflower oil
  • Canola oil
  • Corn oil
  • Peanut oil
  • Generic vegetable oil
  • Grapeseed oil
  • Soybean oil
  • Soy products

In short, if it’s solid at room temperature it’s probably good. If it’s not, it’s probably bad. The exceptions to this rule are olive oil and avocado oil, but since most brands cut their oil with other oils (and don’t show it on the label) those are often bad choices too.

The Ketogenic Diet

Once you’ve completed 4 weeks of low-carb, if you are still wary of fasting let’s try the ketogenic diet. If you can handle keto, you can probably handle fasting. This will also let you learn how to augment fasting if you need to.

Ketogenic diets involve getting less than 5% of your daily calories from carbohydrate, and more than 70% from fats.

If your body enters ketosis (where you start using ketones, a byproduct of fat metabolism, as a replacement for glucose) as a result, you are successfully doing a ketogenic diet.

When most people start ketogenic diets, they experience something called the keto flu. As your body burns fat, it also dumps your muscle glycogen resulting in rapid water loss. The loss of electrolytes, combined with releasing toxins that were stored in your fat, can create flu-like symptoms.

This can be assuaged by supplementing electrolytes properly. My top recommendation is the LMNT product by Robb Wolf. It contains an optimal amount of sodium, magnesium and potassium designed for low-carb and ketogenic athletes. It also tastes great.

Now that you’re doing Keto, continue for a month and see how you feel. You may naturally start intermittent fasting without even realizing it.

Feast Day

The last tip I’ll offer is to have a weekly feast day. One day of the week, don’t measure your carbs. You should still eat whole foods and prioritize quality, but don’t worry about your macros.

Prolonged calorie deficits can cause your metabolism to lower itself, making it harder to burn fat (and use energy.) To avoid this, a weekly day of eating more than usual can help.

This is also a good time to get healthy carbs into your diet and replenish muscle glycogen stores. Carbs do have a helpful role in our nutrition, from electrolyte management to faster energy metabolism for exercise. While keto and fasting can be your main tool, feast days add a powerful bonus to the picture, especially if you are an athlete.

Some great carbohydrate sources are sweet potatoes, honey, japanese yagi yams (also known as japanese sweet potatoes. Thank me later.) Squash, pumpkin, etc. Also small amounts of sweet and nonsweet fruits.

For Women: Keto, Low-Carb, & Feasting Before Your Cycle

Photo by Jon Ly on Unsplash

At this time there is little research on the effects of fasting in women, but what we do have paints a different picture than of men. In men, fasting improves insulin sensitivity, but in women it often makes it worse. Fasting also tends to turn off fertility, and may stop one’s ovulation cycle.

Though fasting does help with weight loss, in women it causes more loss of muscle than simple caloric restriction.

The only area where fasting has been shown to be equally beneficial for women is as an aid for cancer treatment alongside chemotherapy. With all of this said, I think there is a role for fasting for both men and women. In hunter-gatherer societies, it is common for women to fast.

But I think the occasions for fasting and the role it plays are different.

Think about it. Men would typically go out on a hunt, likely fasted. This explains men’s ability to do intermittent fasting. Women, on the other hand, would spend more time in the village or tribe where they had access to food or were caring for children.

Fasting tends to turn off fertility markers in women, probably because it is very biologically expensive to be pregnant and the body wants to prevent pregnancy during a famine.

However, famines do happen, so I’m sure fasting has benefits for women. I just think that fasting should be looked at as a more occasional tool here, and more focus might be placed on diet. When should you fast? Once a month for 24 hours, if you are already fat adapted, and it doesn’t make you feel unhealthy. Do not fast during your period or the week prior. And understand that the purpose is not weight-loss, but longevity.

If weight loss is your goal, I suggest pursuing a low-carb diet and then using cyclical ketogenic diets, not fasting.

Another note: Women have a cycle, and tend to respond better to carbohydrate than men at different times in this cycle. During the week before your period, I suggest exiting keto and increasing your carbohydrates. Think of it as a feast week. There’s a reason women often crave carbs during this time. As long as you eat whole foods, this is the time to listen to those cravings.

Another good reason for feast days and the pre-cycle feast week is that Ketogenic diets can have the same fertility-halting effects in women as fasting. Carbs help temper this. Just remember that female biology is much more unique than male biology because of the hormone cycle, and we should not treat women like they are just small men.

For a great resource on this, I strongly recommend the book Roar by Dr. Stacy Sims.

Intermittent Fasting & OMAD

Intermittent fasting means eating during a small window during the day. This allows you to enter a physiologically fasted state while maintaining your daily routine. One Meal A Day (OMAD) just takes this to the next level by, you guessed it, eating only one meal a day.

The big advantage here is that you can do this type of eating every day without lowering your calorie intake. To effectively perform intermittent fasting you need to go at least 12 hours without eating, and preferably 16.

Your body enters the fasted state around 10 to 12 hours after the last meal, and you’ll get weight loss benefits until you choose to eat again.

Most men do this by skipping breakfast, and eating their first meal between 11am and 2pm. I personally eat for the first time around 11 each day, and have my last meal around 6pm. This results in about 17 hours between dinner and my next meal.

I didn’t start doing this schedule with the intent to perform intermittent fasting. Adhering to low-carb, keto, and carnivore-ish diets resulted in naturally skipping breakfast. One awesome thing about these diets is they’re more satiating. You don’t walk around feeling hungry as often, and may naturally begin to fast.

Whatever the case may be, thems the rules.

Want a more pronounced effect? Try OMAD. Have one meal a day.

I suggest doing OMAD for only 2 or 3 days a week as a regular thing, or for 1 to 2 weeks before stopping as a spot exercise. This is because OMAD makes it difficult to hit your daily calorie needs. I don’t care how hungry you are, it’s difficult to hit your daily needs in one meal, and OMAD typically results in a significant calorie deficit.

Of course, if you find that you can eat all the calories you need in one meal, then more power to you. There may be issues with protein absorption, but many people love this eating style.

With both of these techniques, I still recommend weekly feast days. You could even eat breakfast, if you wanted to, but it’s more about higher calories and getting some more carbs in your diet.

24 Hour and Multi-Day Fasting

The next step beyond Intermittent fasting is 24 hour and multi-day fasting.

Here we enter the realm of fasting for longevity, or for extreme weight-loss or metabolism improvement. If you are generally healthy, feel good on a keto diet, regularly intermittent fast without issue, or have medical supervision, you can do a 24 hour fast as often as once a week. I used to do 24 hour fasting every sunday, and the mental clarity I felt was great.

I don’t recommend hard exercise during a 24 hour fast. This is a good tactic for a recovery day or with light exercise.

Some tools that can help:

  • Electrolytes such as LMNT by Robb Wolf
  • Magnesium glycinate, malate, or threonate (or a combination thereof)

You can also do a modified 24 hour fast by consuming MCT oil throughout the day. I like pure capryllic acid and use the Brain Octane product by Bulletproof labs. This pure fat will keep you in a fasted state physiologically while providing calories to stave off hunger.

Multi-Day Fasting

For multiple day fasts, I definitely suggest using magnesium or electrolytes alongside your fast. A good timeline would be a 3 or 4 day fast every quarter (every 3 to 4 months) if you are healthy and tolerate fasting, or have medical supervision.

The most extreme would be to water fast, meaning you only consume water for 3 or 4 days. I suggest, again, taking off from training during this time. In general people feel the most hungry on day 2 but proceed to feel fine on day 3 and 4, often citing great focus and mental benefits.

Not sure about water fasting? There are some alternatives that allow much of the benefit without as much of the pain.

I love doing bone broth fasting, where I’ll go for 3 or 4 days consuming only bone broth. To make bone broth I suggest getting a few pounds of beef bones from a grass finished source like White Oak Pastures, Belcampo, or a local grass-fed farm. Grass fed is important here. Our bones are one of the areas where we store toxins such as heavy metals. If your beef bones are from grain fed cows, the likelihood of toxin exposure is higher due to the poor conditions of feedlots.

Simply cover the bones with enough water to submerge them, get some salt in there (you can even use the LMNT product), pour in a splash of white vinegar (pulls calcium and other nutrients out of the bones and into the broth,) and simmer in a stockpot or use a slow cooker for 24 hours. You can also use a pressure cooker for 7 to 8 hours. You can add vegetables and spices if you like. Personally I go raw.

Now, consume only bone broth for 3 or 4 days. I find this much easier than water fasting while still getting most of the benefits. Bone broth has tons of awesome stuff for your body too. Glucosamine for your joints, tons of bioavailable nutrients and minerals, not to mention just being tasty.

One of the special benefits of such a fast is for your gut microbiome. Most people think we heal our gut by feeding the good bacteria inside, but research shows that it’s usually more effective to starve the bad bacteria. Dr. Michael Ruscio discusses at length how gut healing is more about removing bacterial overgrowths, and one of the most powerful tools is to fast for several days.

This helps to give the gut a break. Our ancestors would have regularly fasted, yet we often eat for our whole lives without a day off. If you have a leg injury but keep hiking, it’s not gonna get better. That’s kinda what it’s like to eat regularly with an unhealthy biome.


Fasting is great. If you’re a guy. If you’re a girl, it can be more complicated, but it still has its uses.

For men though, fasting is one of the best ways to lower inflammation, lose weight, optimize your insulin sensitivity, and kick some ass. This may be why many male top performers naturally begin to skip breakfast, unintendingly participating in intermittent fasting.

If you want to be more scheduled though, try to go 16 hours from your last meal of the day to the first meal of the next day. This will result in 4 hours in the fasted state, every day, without having to cut calories.

For more extensive fasting, a fat-adapted or otherwise health individual can do a 24 hour fast every week. This can help speed up metabolic healing and garner more benefits. If you do not feel ready for that, focus more on your diet. Low carb and keto are great tools for men who want to get there body better prepared for fasting without actually fasting.

Beyond this is the multi-day fast. Medical supervision is a must if you are addressing disease or significant obesity, but if you are healthy, tools like electrolytes or consuming only bone broth can help with this process.

Longer fasts are going to be more beneficial for things like improving your gut biome and getting anti-cancer benefits. I recommend doing a multi-day fast no more than once a quarter unless you are very well informed on the topic.

To sum it all up: Aim for lower carbohydrate and keto diets as a general tool. Men can also aim for daily intermittent fasting. Once you are fat-adapted, 24 hour fasts and multi-day fasts can be thrown into the mix.

Women should be more careful with fasting, as it does not promote fertility and may even worse insulin resistance. It should be used as more of a gut-health, detoxification, or longevity tool than a weight loss tool. At least until we have more research about how to do it right.

Whether male or female, you can get many of the benefits of fasting from dietary changes. Try the keto diet. Include higher carb feast days weekly, and have a high carb week before your period if you are female. This is an awesome way to improve your health without the stressors of fasting.

Train Hard, Fight Easy

keenan eriksson
Keenan’s singular purpose is to help as many people as possible achieve optimal physical and mental health. He believes biology and psychology are linked, and that by providing a healthy environment for the body we are more likely to fulfill our personal potential through a happy and optimized life. He healed from chronic fatigue syndrome, in two years, despite being bedridden and having a minuscule income. You can find him dropping mad knowledge at Keenan Eriksson Fitness. And you can check him out on Episode 30 of the HRD2KILL Podcast


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