The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting

by Jason Fung

In this way, triglycerides provide energy in the form of fatty acids, ketones, and glucose—enough for the entire body.

Simply put, bariatric surgery is surgically enforced fasting.

Head-to-head studies reveal that fasting is actually superior to bariatric surgery in both weight loss and reduction in blood sugars.

In essence, fasting is bariatric surgery without the surgery.

Type 1 diabetes is an autoimmune disease. For unknown reasons, the body’s own immune system attacks and destroys the insulin-producing cells in the pancreas, leading to a severe insulin deficiency.

Type 2 diabetes, on the other hand, is a dietary and lifestyle disease. In response to frequent high blood sugar, the body produces excessive insulin, which leads to insulin resistance—just as we stop being able to smell a particular odor in a room after a while, the body stops being able to respond to insulin’s signals after prolonged exposure to excess insulin.

Because type 1 diabetics lack insulin, for them, insulin injections are a life-saving treatment.

Allen’s “starvation treatment” was widely considered the best therapy (dietary or otherwise) until the discovery of insulin in 1921.

Joslin, the first American doctor to specialize in diabetes and likely the most famous diabetologist in history, founded the world-famous Joslin Diabetes Center in Boston

Over the past thirty years, the rate of type 2 diabetes has increased significantly in both sexes, in every age group, in every racial and ethnic group, and at all education levels.

in 2012, 14.3 percent of American adults had diabetes and 38 percent had prediabetes, for a total of 52.3 percent.

Interestingly, visceral fat, fat that’s stored in and around the organs, likely plays a large role in type 2 diabetes.

Consider, for example, the effect of wartime starvation on type 2 diabetes. During both World War I and World War II, the mortality rate from type 2 diabetes dropped precipitously.

In a head-to-head comparison, fasting lowered both body weight and blood sugar better than bariatric surgery.

It is well known and well accepted that type 2 diabetes is a disease of insulin resistance.

One of insulin’s main jobs is to move glucose from the blood into the tissues, which use it as energy.

Insulin is the body’s subway pusher, shoving glucose into the cell no matter the consequences.

But the main cause of the insulin resistance is that the cell was already overflowing with glucose.

Because the cell is overfilled with glucose, glucose spills out of the cell, leading to increased blood glucose levels.

the type 2 diabetes is just getting worse. The medications only help control blood sugar; they don’t address what’s causing type 2 diabetes.

If the core issue is that glucose is overfilling the cells, then the solution seems rather obvious: get all that glucose out of the cells!

(Remember, it’s the glucose in the tissue cells that’s the underlying problem—without that, the glucose in the bloodstream is no longer a problem.)

First, you need to stop putting glucose into the body. You can achieve this with very low carbohydrate diets or ketogenic diets.

Second, your body needs to burn off the excess glucose. Fasting is again an obvious solution. Your body requires energy just to keep all the vital organs, such as the heart, lungs, liver, and kidneys, working.

At its core, type 2 diabetes is a disease of excessive glucose, in our blood but also in our bodies.

Most medications unrelated to blood sugar can be taken during fasting, though you should still discuss them with your physician first.

One of the benefits of fasting is that it helps very strongly insulin-resistant/hyperinsulinemic people finally tap into their stored body fat for energy—plus there are the myriad other benefits that come from reducing insulin levels.

The truth about obesity, insulin, and diabetes was almost the total opposite of everything I had learned in university about nutrition.

Life is all about finding a balance. Feast and fast. It has been easy for me to maintain my weight loss and health since.

Our goal is to try to limit how much insulin the body needs to produce each day.

help transition patients to a high-fat, moderate-protein, and low-carbohydrate diet.

but there are many other benefits, including autophagy (a cellular cleansing process), lipolysis (fat-burning), anti-aging effects, and neurological benefits.

In one study of mental acuity and fasting, none of the factors measured—including sustained attention, attentional focus, simple reaction time, and immediate memory—were found to be impaired.

Interestingly, there was even increased brain connectivity and new neuron growth from stem cells.

Compared to normal mice, mice on an intermittent fasting regimen showed less age-related deterioration of neurons and fewer symptoms of Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease.

In addition, insulin levels have an inverse correlation to memory—that is, the lower the insulin level, the more memory improves.

So fasting provides neurological benefits two ways: it decreases insulin and leads to consistent, maintained weight loss.

There appears to be significant research indicating a dramatic drop in inflammation, improvements in insulin signaling, and a near total “reset” of immune function with fasts of 3–5 days.

While we often focus on new cell growth, we sometimes forget that the first step in renewal is destroying the old, broken-down cellular machinery.

These unwanted cellular components build up over time if autophagocytic processes are not routinely activated.

Even as little as 3 grams of the amino acid leucine can stop autophagy.

The mammalian target of rapamycin (mTOR) pathway is an important sensor of nutrient availability.

autophagy. In other words, the constant intake of food, such as snacking throughout the day, suppresses autophagy.

when mTOR is dormant—when it’s not being triggered by increased insulin levels or amino acids from ingested food—autophagy is promoted.

The oldest and most worn-out cellular parts get discarded, and amino acids from the broken-down cell parts are delivered to the liver, which uses them to create glucose during gluconeogenesis.

This is why the strongest stimulus to autophagy currently known is fasting, and why fasting alone, unique among diets, stimulates autophagy—simple caloric restriction or dieting isn’t enough.

Simply put, fasting cleanses the body of unhealthy or unnecessary cellular debris.

At the same time, fasting also stimulates growth hormone, which signals the production of some new snazzy cell parts, giving our bodies a complete renovation.

Since it triggers both the breakdown of old cellular parts and the creation of new ones, fasting may be considered one of the most potent anti-aging methods in existence.

Autophagy also plays an important role in the prevention of A...