extremely dangerous. In fact, long-term fasting starves the body of essential nutrients, causes the body to shut down (metabolism slows dramatically), and can be life threatening.
CLARIFYING STARVATION MODE: HINT, IT’S A MYTH
This nutrition myth pervades the dieting world, with confusion occurring because the term starvation mode means many different things to many different people. The often-repeated belief is that when trying to lose weight, you shouldn't drop your calories too low, because your body will go into starvation mode, and you’ll hold onto fat and stop losing weight. This is 100 percent false. You don’t gain weight or fat from eating too little. You won’t go into a starvation mode during your intermittent fasting regimen.
Consider these facts:
The starvation mode refers to the reduction in metabolic rate that occurs when the body is starved for long periods of time, such as observed in severely malnourished people with anorexia nervosa.
During severe starvation, the body does in fact slow its metabolism down, dramatically; the body's natural physiological response to an extreme reduction in calorie intake, a technique the body uses as a survival mechanism. Without it, humans would have become extinct thousands of years ago.
The starvation mode does not occur during most people’s dieting experiences. Dieting, even low-calorie diets, don’t catapult your body into starvation mode.
When you lose weight, your body will require less calories to maintain your new body weight because there's less of you, so you require fewer calories, a concept referred to as metabolic adaptation.
You can offset this metabolic adaptation and keep your metabolism as high as possible when losing weight by adding in strength-training exercise and making sure you eat enough protein.
However, intermittent fasting differs from traditional fasting. As the name suggests, intermittent fasting refers to alternating periods of fasting with periods of eating. It’s a broad term, encompassing several specific types of short-term fasting protocols. The common theme among intermittent fasting regimens is that people periodically abstain from eating for periods longer than the typical overnight fast. Individuals either fast during a certain window every day or block out certain days of the week. These short eating rest periods allow the body’s numerous systems to rest and reset without triggering the risk of malnutrition and metabolic slowdown that accompanies severely restrictive long-term fasting regimens.
Here I take a closer look at what intermittent fasting is and some of the dos and don’ts of getting started on your intermittent fasting journey.
Recognizing the nuts and bolts of intermittent fasting
Here are the key principles of intermittent fasting lifestyle methods:
All intermittent fasts restrict eating and drinking for set, short periods of time. Every method of intermittent fasting outlined in Part 3 has feasting and fasting periods that vary, depending on the regimen.
The intermittent fasting approach involves alternating periods of eating and fasting. These time periods differ depending on the variation of intermittent fasting, so you choose the method that works best for your lifestyle.
All intermittent fasting protocols are safe and effective for healthy individuals. Each of the methods in Part 3 are safe and have been shown to improve a person’s health and well-being, if practiced correctly.
All intermittent fasting protocols have certain rules you must follow during your fasting window. These steps include drinking plentiful amounts of water, black coffee, tea, and any other non-caloric beverage during your fasting window; just no solid foods allowed. Make sure to stay hydrated during your intermittent fasting periods.
All intermittent fasting protocols prohibit you from eating excessive amounts of junk food during your eating windows. This habit will negate the many benefits of intermittent fasting. The biggest mistake people make is eating too much and eating unhealthy foods during their eating periods.
Intermittent fasting can be practiced for health and fitness and not necessarily for weight loss. Although weight loss is one of the most common reasons for trying intermittent fasting, many people choose to get leaner and fitter and tap into the numerous health benefits intermittent fasting provides without the goal of losing weight. In fact, some follow an intermittent fasting program with the primary goal of gaining muscle weight and losing body fat.
Pregnant or lactating women
Individuals who have eating disorders
Individuals with type 1 or type 2 diabetes unless working with their healthcare professional (physicians must be consulted if you have any underlying chronic disease)
Individuals using medications that they must take with food, unless working with their physician
High-level endurance athletes
Elderly individuals with balance issues
Children
Chapter 7 discusses in greater detail who should and shouldn’t follow an intermittent fasting plan.
Delving deeper into how intermittent fasting works
Intermittent fasts cycle between periods of fasting with periods of eating. Whether or not you’re fasting, the body still requires energy to run efficiently. The body’s main source of energy is a sugar called glucose, which typically comes from carbohydrates such as grains, fruits, vegetables, and even sweets. Both your liver and muscles store the sugar and release it into the bloodstream whenever the body needs it.
Looking closer at the physiology
To understand how intermittent fasting works, you need a quick adaptive physiology refresher. Because food wasn’t always abundant, and sometimes wasn’t available at all, the human body was forced to adapt to fasting involuntarily — and then, when Stone Age humans found food, they would feast. Because of those evolutionary conditions, human bodies evolved to permit their bodies to thrive by adapting to those cycles of feasting and fasting. In order to survive in such environments where food was scarce, humans had to possess the ability to quickly shift their metabolism from fat storage to fat breakdown for energy. This metabolic flexibility became built into human’s genetic code, producing a system where energy was stored in the form of body fat when food was available and then easily accessed for energy to enable humans to perform at a high level, physically, during extended periods when food wasn’t available. This pattern enabled human brains and bodies to function optimally in a food deprived/fasted state, giving the human race a survival advantage.
Scientists have hypothesized that the human body’s adaptive benefits of intermittent fasting led to the superior cognitive capabilities (brain power) of humans compared to other mammals. These brain adaptations facilitated human’s ability to invent tools, novel hunting methods, animal domestication, agriculture and food storage, and processing.
Because intermittent fasting patterns can replicate the feast-or-famine diet of human ancestors, many researchers have now recognized the advantages of periodically fasting (such as increased brain power, physical enhancements, and disease prevention) for the multitude of health benefits this lifestyle gives rise to.