Winter Fasting: Are Humans Built for This Ancient Health Hack?

Nov 28, 2022 10:53:01AM

Before humans’ foray into agriculture, our ancestors would have gone long periods without access to abundant food. As the forests wound down for the season and animals tucked themselves into hibernation, people simply had less available to eat. To sustain themselves, they would rely on what they could hunt or store, and stretch it out to make it last throughout the season. 

Our ancestors’ activity levels slowed down too, though. Winter meant shutting in, moving less, metabolism would slow, and it was common to eat less than you would during seasons when food was everywhere and activity was high. 

Some say that those practices kept disease at bay. While it’s not conclusive, there are camps who believe that increased consumption of carbohydrates and a steady supply of food, both from agriculture, can lead to health problems. They believe that the break from digestion allows the body to redirect energy and resources to repair and waste removal, which contributes to overall health. This is all speculation, but there is some evidence to support some of these ideas. 

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Are humans built for winter fasting? 

The idea of winter fasting doesn’t mean that our ancestors ate nothing during the colder months. It means that they didn’t have as much fresh food available so they ate what they could hunt or store, and they had to make it last. So, that means they had to ration among the family, and everyone ate less than they would when the growing season was plentiful. 

Humans have two fuel systems

Are we built for that eating pattern? Is it more natural? Some signs point to yes. In times of scarcity, our bodys switch from running on glucose (sugar and carbs) to running on ketones (from dietary or stored body fat) for energy. This ability to switch fuel sources is hardwired into our biology so that we can survive famines or tough seasons. 

Autophagy as a disease defense

Additionally, when we have less food available, our cells will “burn” damaged cells, old cell parts, and waste (that’s cellular waste products, not to be confused with bathroom waste!) for energy. That has two benefits: first, we get that extra bit of energy that we are missing from food, and second, damaged cells and cell parts could contribute to disease. This process is called autophagy, which loosely translates to “eating self.” Autophagy has been studied as a defense against cancer and other disease processes. Autophagy is also of interest to aging researchers, as there is emerging evidence that it could slow aging processes. 

Ways to fast over winter

If you want to give it a try, pay close attention to how you feel while you’re doing your winter fast. And remember, going extended periods of time with no food isn’t the goal—that’s not what our ancestors did and starving yourself could have the opposite effect on your metabolism and health. Instead, you can try one of these formats (consult a qualified medical provider first):

  • Intermittent fasting. Usually people will restrict eating to a specific window each day, taking a 12, 16, or 18-hour break from digesting. Usually, the break spans night so that you can sleep through most of it. 
  • One meal a day. One meal a day, or OMAD, involves taking in a full day’s calories in one sitting, or a in very short window of time (1-2 hours). You don’t eat less. You eat as much as you would eat in a day, all at once. 
  • Extended fasting. Extended fasts are multi-day fasts (48-72 hours), that people do occasionally. Women may have a harder time with extended fasting because their hormones are more sensitive to changes. 
  • Calorie restriction. Calorie restriction involves eating smaller meals and fewer calories, which is closer to what our ancestors would do over winter. Consult a doctor or dietician to find your nutrient requirement.  

Do’s and don’t’s of fasting

  1. Don’t starve yourself and call it fasting. You could miss out on important nutrients or slow your metabolism if you’re not eating enough. That could make it hard to maintain a healthy body weight. If you suspect you might have an eating disorder, call your doctor right away, even if you’re not sure. 
  2. Don’t do any type of fasting while pregnant or nursing. 
  3. Don’t overexert yourself while fasting. 
  4. Don’t binge eat after your fast. Start slow and work your way back up. 
  5. Do listen to your body. Pay attention to your body for signs that something’s not right.
  6. Do hydrate! You may lose more water and electrolytes due to the fasting process. Replenish often. 

Remember, at first, this is experimentation, and sometimes experiments don’t work out. Pay attention to how your body reacts, and if you need to pull the plug and eat something, allow yourself that flexibility. 


Federico Pietrocola, Jonathan Pol, Erika Vacchelli, Elisa E. Baracco, Sarah Levesque, Francesca Castoldi, Maria Chiara Maiuri, Frank Madeo & Guido Kroemer (2016) Autophagy induction for the treatment of cancer, Autophagy, 12:10, 1962-1964, DOI: 10.1080/15548627.2016.1214778

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