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Intermittent Fasting, Part 2


Over the past 100 years, numerous intermittent fasting (IF) studies have shown a remarkable improvement on aging and life span in animals. Initially thought to be caused by the reduced production of free radicals and weight loss, it is now understood that there are numerous other cellular phenomena going on. An excellent article in the New England Journal of Medicine states that,
“Intermittent fasting elicits evolutionarily conserved adaptive cellular responses that are integrated between and within organs in a manner that improves glucose regulation, increases stress resistance, and suppresses inflammation.”

They continue:

“Periodic flipping of the metabolic switch not only provides the ketones that are necessary to fuel cells during the fasting period but also elicits highly orchestrated systemic and cellular responses for carry over into the fed state to bolster mental and physical performance as well as disease resistance.”

As the New England Journal of Medicine review article describes, autophagy is greatly enhanced during IF. With fasting, our cells become more adept at cleaning themselves and recycling components. Dr. Yoshinori Ohsumi, who specializes in autophagy, was the recipient of the 2016 Nobel Peace Prize in Medicine for his discoveries of the mechanisms of autophagy: that each cell in our body has the capability of destroying its own contents and recycling them. This concept of “self eating” was first observed in the 1960s. He is a smart guy (and I’m told, also a good fly fisherman).

Dr. Ohsumi’s discoveries open the door for a new paradigm of understanding about how the cell responds to a host of physiological processes and stressors like starvation and infection, and how autophagic processes affect serious illnesses like cancer and neurologic disease.

Different IF regimens

Fasting, like everything else in life, should be kept simple. In general, the longer someone spends in a fasting state the more robust the benefit. There is no widely accepted superior method of IF, but there are a few popular and widely practiced approaches.

Leangains, 16:8

This method of fasting (developed by Martin Berkhan, a Swedish nutritional consultant, bodybuilder, and model) is probably the most popular IF method. It involves 16 hours of fasting and eating within an 8 hour window. It’s pretty much just eating lunch and dinner.

The Warrior Diet, 20:4

This is based on the purported eating patterns of ancient warriors, who consumed little during the day and feasted in the evening. It was created by Ori Hofmekler, a former Israeli special forces member turned fitness and nutrition educator. It specifies 20 hours of fasting and eating a large amount at the end of the day, in a 4 hour window.

Eat Stop Eat

This is the title of a book written by Brad Pilon, another bodybuilder, who has a graduate degree in human biology and nutritional sciences and is a leading and vocal advocate of IF. This method involved fasting for an entire 24 hours, 2 days per week. Many find this method more difficult, but certainly a deep level of fat breakdown (lipolysis) and fat burning (beta oxidation) occur.

The Non-Body Builder, Non-Model, Middle-Aged, Endurance Hack, Nobody Method

This is my regimen. It’s very complicated and nuanced. Also highly evidence-based and basically the greatest thing ever. Sometimes I have really fatty coffee in the morning. Sometimes I do not have fatty coffee. But I always have coffee. I hardly ever eat breakfast. Monday through Thursday I eat two meals a day, low-carb high-fat. Friday through Sunday usually “OMAD”, one meal a day. I am rarely hungry, commonly exercise on an empty stomach, and never count calories or measure ketones. This signature method of mine also can encompass much longer fasts. I am looking out the window right now, with pride, at a garden fence I built while fasting for 5 days. It’s a terrible fence, all uneven and falling apart. It doesn’t even keep the deer out, which was its original intent. But hey, I was lightheaded and kept falling off the ladder while pounding posts. I absolutely love that my day no longer revolves around food. It is freeing, liberating, and time saving. And I was never well suited for physical labor anyway.

Tips for IF

Most individuals who’ve adapted to a LCHF (low carb, high fat) way of eating can seamlessly fast, although that’s not a requirement. I have written about eating this way many times and I think it is the healthiest “diet.” I have also written about the concept of “fat adaptation,” the cellular biochemical state of fat burning efficiency. It takes a while to develop this, which is one of the principal problems of many of the ketogenic diet studies on athletic performance: the athletes were simply not allowed the time to fat-adapt. The more adept we are at burning fat, the more pleasurable the fasting experience. Staying well hydrated is critical. Drink at least 2 liters of water daily. Tea and coffee are also excellent choices. Green tea in particular yields favorable chemicals to stimulate metabolism and weight loss. Coffee really should have its own article. Both caffeinated and decaffeinated coffee show greater suppression of hunger than equivalent amounts of caffeine mixed with water. This implies there are numerous other beneficial compounds within coffee.

Embrace the grind. Understand the benefits of fasting and understand that nothing bad will happen because you are hungry. Also realize (and keep telling yourself over and over) that the hunger will pass relatively quickly.

How to Break the Fast

With shorter duration fasts (24 hours or less), there really is nothing to “break;” just start eating again. Be aware that the urge to eat is based more on the psychological need to do so than on hunger. Overeating can lead to gastrointestinal issues. Be mindful, don’t binge, and choose low glycemic, nutrient-dense food.

Can I exercise during a fast?

Yes. In fact, it’s recommended. There are actually many similarities between exercise and fasting, and doing them together compounds the benefits. There is a misconception that when we exercise, we must provide caloric fuel. Except for higher level endurance training and competition when the nuances of proper fueling become more important, the liver is capable of creating glucose through gluconeogenesis. Furthermore, muscles are able to directly use fat for fuel. That’s why exercising on an empty stomach accelerates the reduction in body fat percentage that confers such health benefits.

While our liver glycogen stores are naturally depleted during sleep and fasting, muscle glycogen stores remains intact. Fasting three hours prior to exercise will increase insulin sensitivity and fat burning.


Strive to increase the amount of time spent in a fasting state. Many people find that with a little bit of practice, breakfast can be routinely skipped. Eating two delicious nutrient-dense low-carb high-fat meals per day (a later lunch, and a larger dinner) seems to maximize fasting’s benefits for most people. A great way to start is to first try LCHF eating. Then slowly move back the first meal.

Many neurological and hormonal forces within the body all conspire to elevate insulin levels. Why? Because it’s an anabolic, survival hormone, and our brains really, really want us to survive. Consumption of a LCHF diet has a powerful impact on insulin secretion, metabolism, and overall health. The addition of IF further accentuates these effects. Many authorities, including Dr. Fung, feel it is the most powerful modality to reduce insulin, thus allowing the burning of fat. And it’s entirely within our control. Your control.

References available on request

Back to Endurance News Weekly


Message: Nice articles. I have been contemplating IF for a while – when I used to do 16:8, two days a week, I would be starving at night for dinner and have trouble getting full. Do you recommend using this fasting pattern daily or a few days per week? Will the hunger at night get better? Thanks!

Answer: Thank you for your thoughtful questions and sharing your experience. I’m not surprised you had this experience with compressed eating only two days a week. It takes about 4-8 for the body to adapt and the hunger patterns that go with it. IF does not have to be practiced religiously or every single day – doing IF 5-6 days per week with one or two “regular” days would be more effective compromise. Absolutely, the hunger pangs and cravings go out the window after the first few weeks. Most people never make it through this adaptive phase, which is why 90 some percent of calorie restriction and or timed eating fail. BDF

Hammer Nutrition

Message: Does fasting also include no coffee ,recovery drinks also say in mornings after w/out

Answer: Black coffee does not trigger insulin or digestion, so no worries there. However, a recovery drink with carbs and protein definitely gets the body’s energy factory up and running, so that would be breaking fast. Depending on how early you workout, opening your eating window at the start of workout if going hard or the conclusion if not going hard or for too long and finish eating for the day with a mid-afternoon meal/early dinner. Takes lots of discipline, but the fastest way to get super lean. BDF

Hammer Nutrition

Message: Are the benefits the same if you skip dinner as your fasting time and eat breakfast and lunch?

Answer: Thank you for your question. I would suggest that the benefits of eating your daily calories in the early and midday hours (for example, using an 8 hour window, eating between 7 am and 3 pm) can be ideal in a couple of different scenarios, but also somewhat challenging. First being someone who does most/all of their training in the early AM and needs calories during and a recovery meal following. The second scenario being someone who wants to lose weight and or get leaner. That being said, putting the fork down and 3 pm and continuing on with your day for another 5-6 hours takes a lot of discipline for the first 4-6 weeks while your body adapts. Conversely, this eating format would not work very well for athletes who train later in the day and for those for whom dinner is an important and necessary part of social/partner/family time. BDF

Hammer Nutrition

Message: I have been doing IF since mid April. I am down 30 pounds and feeling better than I have in years. At 62 my weight is back to what t it was when I was deployed in Iraq in my 40s. Exercise is coming back. I see this as lifestyle change and don’t anticipate going back.

Answer: Thank you so much for this feedback, I’m stoked to hear the benefits you’ve already seen in the five months since you started. When you see the effects, it’s pretty easy to stay with it! I’m in year two and also plan to continue as well. BDF

Hammer Nutrition

I love this article, too! I’m not very good at IF, but it’s probably because I don’t eat low carb. I’m more into extended fasts (10 days or so), because I lose my hunger after the first day, lose my psychological “hunger” a day later. After that, the rest is easy.

I look forward to more articles on fasting (IF or otherwise) related to exercise.

Matt Bell

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