Fasting or intermittent fasting (IF) has widely become an accepted driver of many health benefits. While exercise and good nutrition have long been pillars for a healthy lifestyle, when and how often we eat are quickly becoming a recognised contributor.
The definition for fasting can vary, however typically requires the abstinence from food and drinks for a period. Overwhelming scientific studies have demonstrated promising potential for human health and longevity. Fasting has shown to cleanse toxins and force cells into processes not usually stimulated with steady food consumption.
"When you fast, you turn on defenses. It's not that blood flows better or just that insulin sensitivity changes. You are turning on every cell's defenses against DNA damage, toxins, and everything that causes diseases. It seems that these defenses have a way to slow down the negative effects."
– Dr. David Sinclair, A.O., Ph.D. Department of Genetics Professor, co-Director of the Paul F. Glenn Center for Biology of Aging Research at Harvard Medical School.
This makes sense from an evolutionary perspective of millions of years, before farming and agriculture provided most food sources. Prior to only 10,000 years ago, food predominately was either found or hunted. As a result, human bodies adapted to longer periods without eating while still having stores of energy to survive.
Without its usual access to glucose, the body forces cells to other means of energy production such as gluconeogenesis (natural process of producing its own sugar). The liver then helps to convert non-carbohydrate materials, amino acids, and fats into glucose energy. The conservation of energy during fasting increasing basal metabolic efficiency, lowering both heart rate and blood pressure.
Renowned longevity experts like Dr. David Sinclair found fasting activates sirtuins, which have been shown to aid increased lifespan. Another molecule important for longevity is decreasing mTOR (mammalian target of rapamycin) levels, so that old proteins can be recycled to make new ones. Eating less often positively regulates both sirtuins and mTOR, the critical components to achieving longevity.
By putting the body under this mild stress, cells adapt and enhance coping abilities, becoming stronger and inducing cellular repair. Like exercise, when our muscles and cardiovascular system is stressed, it becomes stronger.
Identifiable benefits by regularly fasting include:
Promotes blood sugar (insulin) control and prevention of type 2 diabetes
Reduces blood pressure and cholesterol (healthy heart)
Boosts cognitive performance
Induces cellular repair
Protects from associated chronic and metabolic diseases
Reduces oxidative stress and inflammation
Linked to delayed aging and extending longevity
Improves overall fitness
Supports weight loss and decreases obesity
Benefits certain cancer patients (and prevention) — Studies show fasting during chemotherapy jump-starts the immune system and exposes cancer cells. More of the toxic cells are then expelled and replaced with new, healthy ones.
Commonly practiced fasting types are:
Time-Restricted (Intermittent Fasting). Limit calorie intake to a specific timeframe, aligning with circadian rhythm (body clock). Typical eating times with this method fall between an 8-to-12-hour period each day. Some limit the eating window to only six hours and fast for 18.
Intermittent Calorie Restriction. Reducing the number of calories consumed each day, forcing the body into a short and intensive therapy.
5:2 Fasting. Eat a normal diet five days in a week and fast completely for two full days.
Ketosis Fasting. Limit calorie intake to specific (very low carbohydrate) foods, depleting glycogen stores and entering ketosis. It is believed this surpasses a two-day fast as it allows the body to remain in this state of cleansing for longer periods.
Ketosis refers to a metabolic state when carbohydrates are replaced almost completely by healthy fats. The body then becomes incredibly efficient at burning fat to supply energy. This process also occurs later into a fasting cycle when the body begins burning stored fat as its primary power source. An ideal mode for weight loss and balancing blood sugar levels. Entering into ketosis requires a ketogenic (keto) diet and only sticking to certain foods.
Can you consume anything during a fast?
Virtually all foods, beverages (excluding water), supplements and even some vitamins are expected to break a fast.
Strictly speaking, any amount of calories will break a fast. Sticking to water is a safe option and highly encouraged as it is important to remain hydrated. In humans, it appears that autophagy (reusing old and damaged cells) does not remain as active when any calories are consumed and likely a water-only fast will maintain the maximum benefit.
Drinks with minimal to no calories that can be enjoyed during a fast include:
Water (still or sparkling): contains zero calories and can be drunk as much as preferred
Teas and black coffee (no milk/cream): both contain very few calories
It is important to remember that fasting may not suit everyone. People who may want to avoid fasting (or speaking with a health professional first) may be:
Pregnant mothers before, during and after delivery (including mothers who are breast-feeding infants). Particularly those who may be anaemic, emaciated, or can’t afford well-balanced and nutritious food.
Persons who eat far less than their actual requirement or are under or malnourished.
Weak, emaciated and starved children who are in their growth stage.
Persons suffering from low blood pressure and low sugar levels in their blood.