Fasting: Allowing the Body to Feast from Within

The word “fasting” stems from the Old English root “fæsten,” which means abstaining from ingesting foods for a selected period. Dating back to 500 B.C., cultures, religions, and practices have incorporated elements of fasting for various purposes. The people of Ancient Greece, with support from physicians like Hippocrates, were among the first documented groups to adopt this practice to maximize spiritual protection and bodily health. For Biblical figures, fasting was a way to connect deeply with God through such demonstrations of devotion. Muslims also honor fasting to cleanse and guard the soul.

Powering Up

You might have heard that carbohydrates from foods like apples and bread help give us a speedy boost in energy. Carbohydrates such as glucose, galactose, and fructose are some ready-to-go sugars metabolized by our cells to create high-energy molecules. This fuels reactions such as creating new biological components, contracting muscles, and even forming our thoughts! In fact, our brain uses 20% of energy manufactured from glucose.

When more glucose is in the bloodstream than immediately required for cellular use, insulin moves the sugar to the liver where it is stored as glycogen, a fast backup energy supply. If we don’t eat for a few hours, blood glucose levels decrease, triggering the liver to turn glycogen back into glucose and release it into the bloodstream. This is one of the many ways our body self-regulates.

Adapting to the Absence of Food

As fasting commences, we still need enough energy to maintain healthy, functional levels of operation for as long as possible. Suppose your tissues used up the stored sugars from your last meal. In that case, our liver performs gluconeogenesis, providing a self-sustaining supply of glucose with organic compounds such as amino acids sourced from protein.

The body begins using fat reserves about 12-36 hours (about 1 and a half days) after our last meal. TAGs (Triacylglycerols) comprise most of the fat stored in our body and come primarily from our diet, such as butter and oil. Although it takes longer for enzymes to break down TAGs than sugars, we forge more energy per gram. This period is when the person fasting reaches a healthy maximum of weight loss from a fast from using storage bases and the accompanying water loss due to metabolic byproducts. After 3 days of fasting, cells begin utilizing proteins from muscle, but adverse health effects on the brain, gut, and metabolism may accompany this stage.

Benefits of Food Breaks

Intermittent fasting is one form of patterned eating that is rising in popularity, especially for people who seek to lose weight. This type of fasting is customizable to days or weeks, one example being the “16:8 Approach” where food is consumed within an eight-hour window, followed by 16 hours of fasting. There are many ways to fast, but regardless of the method chosen, it is important to plan out when the next meal will be, the frequency of food breaks, and ensuring to meet dietary guidelines.

Fasting has been associated with multiple benefits, including decreases in inflammation, waist circumference, blood glucose, insulin resistance, LDL cholesterol and blood pressure. In turn, these outcomes are associated with lowering the risk of developing cardiovascular disease, Type 2 Diabetes, and components of metabolic syndrome such as obesity. Fasting may pose risks for people with certain health conditions, so be sure to talk with your primary care provider if you are unsure if fasting is safe for you.