From June 1965 until July 1966, Angus Barbieri set the world record for the longest fast ever. For 382 days, he did not eat any food!
Yes, you read that correctly: Barbieri did not eat any food for 382 days.
He was frequently supervised by medical professionals, but on the day to day, he consumed coffee, tea, sparkling water, and vitamins.
In the process he lost 276 pounds.
Fasting is an incredibly powerful nutritional intervention.
It’s simple (don’t eat any food) and it’s cheap (no pills or fancy dieting) making it something that everyone can do.
While continuous fasting can be beneficial, recent research into Intermittent Fasting strategies has shown a host of powerful benefits without the long term absence of food.
Human beings have evolved to exist through periods of food scarcity. Unlike traditional Western diets that see us eating three meals a day, premodern humans did not have the luxury of abundant food.
Not only did we not have access to food, but we had to develop physiological strategies to run far, lift heavy things, and be mentally aware in the face of little to no food consumption.
By accessing different types of fuel in their bodies, our ancestors were able to survive when a meal…or two…or three, etc, was not available.
Flash forward to today. By employing this “metabolic shift” frequently into our nutrition regimens, we can reap many health and performance benefits, without sacrificing lean muscle mass.
How the Metabolic Shift Happens
Our brains and bodies function primarily on glucose, carbohydrate in its simplest form.
However, during periods of time with little to no food intake our influx of glucose is absent.
The metabolic shift associated with enormous health benefits occurs when the liver has exhausted its glycogen stores (glucose is stored in the liver in the form of glycogen) usually 12-36 hours after your last meal.
Once this shift occurs, the body shifts from fat storage to fat mobilization, transforming stored fat into free fatty acids and fatty acid derived ketones. These new fuel sources are then transported to muscles and the brain to be used as energy.
How the Metabolic Shift Helps
Intermittent fasting strategies have been shown to
- Burn fat while maintaining muscle.
- Increase cognitive function.
- Reduce blood pressure.
- Increase endurance.
- Reduce pain sensation.
- Improve immune system function.
Strategies to Activate the Metabolic Shift
1. Time Restricted Feeding – Eat only during a certain window of time each day. You can still eat your normal amount of food each day, but it must be within a window of time usually 6-8 hours each day. By building in periods of rest time for your gut, your body will shift over to ketones.
2. Alternate Day Feeding – Eat normally on “even” days, but eat a 500 calorie meal or do not eat completely on “odd” days, or vice versa. This increases the gut rest period thereby allowing a great reliance on ketones, but reduces the frequency of metabolic shift throughout the week.
3. 5:2 Feeding – Eat normally throughout 5 days of the week and then fast 2 days of the week.
Flipping the metabolic switch through various intermittent fasting approaches can be beneficial to most people, but it’s not for everyone. Athletes who are looking to gain weight and/or muscle might find the restricted opportunities for food consumption to reduce recovery and fuel performance. People under 18 who are still growing and continuing to mature should not consistently practice intermittent fasting strategies. Women who are pregnant or breastfeeding will not ingest the recommended amount of nutrients for themselves and their child.
Anton, Moehl, et. al. “Flipping the Metabolic Switch: Understanding and Applying Health Benefits of Fasting.” Obesity (Silver Spring). 2018 February ; 26(2): 254–268 .
Wang and Wu “The Effect of Fasting on Human Metabolism and Psychological Health.” Hindawi Disease Markers Volume 2022, Article ID 5653739, 7 pages.
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