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Lewis HowesUse These FASTING SECRETS To Lose Weight & Prevent CANCER! | Jason Fung & Lewis Howes
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Chapter summaries
What Causes Cancer: Smoking, Diet, and Obesity
Lewis Howes asks about the main causes of cancer. Dr. Fung says tobacco and diet are the two biggest contributors, and that decades of testing fiber, fat and vitamins failed to explain the diet link until obesity was recognized as a risk factor.
- •Tobacco smoke accounts for about 35% of cancers and diet is almost as large
- •Fiber, dietary fat and vitamin supplements were tested and did not explain the diet link
- •The WHO now counts 13 cancer types as obesity-related
- •Obesity and type 2 diabetes raise risk for cancers such as breast and colorectal
- •Radiation, pesticides and sunscreen contribute little at the population level
Genetics, the Seed-and-Soil Idea, and Why Cancer Is a Mystery
Fung explains that genes like BRCA are not a death sentence and compares cancer to a seed that needs fertile soil. He says heart disease outcomes have improved faster than cancer's because we never understood what cancer is as a disease.
- •Healthy, lean people can still get cancer, and much of the remaining risk is poorly understood
- •BRCA breast cancer risk was around 30% in earlier generations versus about 80% in modern America
- •The seed exists in every cell, so lifestyle shapes the soil
- •Cancer arises from our own cells, which makes its origin puzzling
- •Without knowing what a disease is, it is hard to fix, like a car with an unexplained clank
Diseases of Civilization and Foods to Cut Back
Fung says traditional societies such as the Inuit and Africans seen by Denis Burkitt had little cancer until they adopted Western foods. He then lists sugar, refined grains, refined oils and meats, and frequent eating as key concerns.
- •Prevention is realistic, though diet is much harder to use once cancer has developed
- •The Inuit and traditional African populations had little cancer before Westernizing
- •Japanese and Chinese women moving to San Francisco see breast cancer risk roughly triple within a couple of generations
- •Sugar and refined carbohydrates top his list
- •Refined foods differ from natural ones, such as bologna versus grass-finished beef
Insulin, Nutrient Sensors, and Cancer Growth
Fung describes cancer cells as behaving like a separate species that responds to growth signals. Eating constantly keeps insulin and mTOR high, while fasting lowers these signals. He also explains why vitamin supplements didn't help and may have raised cancer risk in some studies.
- •Cancer cells act in their own interest and are seen by the immune system as foreign
- •Insulin and mTOR signal that food is available and tell cells to grow
- •Breast cancer cells grown in a lab wither without insulin
- •Folic acid and beta carotene studies suggested more cancer, like fertilizer producing weeds
- •Obesity and type 2 diabetes both involve too much insulin
Snack Culture and the Fed vs. Fasted State
Fung contrasts the 1970s habit of three meals a day with today's constant snacking. He explains that the body is either storing calories when insulin is high or burning them when insulin is low, and says intermittent fasting simply lengthens the time spent burning stored fat.
- •People in 1970 ate three times a day without snacks, while today's average eating window is about 14 hours 45 minutes
- •High insulin blocks fat burning, so constant eating means stored fat is never used
- •It takes about four hours to switch into the fasted state
- •Intermittent fasting means widening the non-eating window
- •Humans evolved with periods of no food and body fat is stored fuel
Fung's Own Fasting Routine and How Long You Can Fast
Fung describes rarely eating breakfast, keeping a six-to-eight-hour eating window, and doing occasional 24-hour or longer fasts to undo vacation weight gain. He discusses the social side of fasting and how long a person with ample body fat could go without food.
- •He started skipping breakfast in medical school and says there is nothing magical about it
- •He uses a longer fast after holidays or a cruise to return to his normal weight
- •Religious fasts like Lent, Ramadan and Yom Kippur are easier because everyone does them
- •A 12-14 hour overnight fast is a baseline, and a 4-to-8-hour eating window is also possible
- •A person 100 pounds overweight could theoretically go about 200 days on stored fat
Myths: Muscle Loss, Starvation Mode, and Mental Clarity
Fung addresses fears about fasting, saying muscle isn't burned for fuel, that calorie cutting lowers metabolic rate while zero-calorie fasting does not, and that mental sharpness rises. He cites a four-day fasting study showing about 10% higher energy expenditure, along with the Unbroken prisoner anecdotes.
- •Muscle is maintained through exercise, and loose skin after weight loss is excess protein
- •Cutting 500 calories a day causes the body to cut its expenditure similarly
- •In a four-day fasting study, metabolic rate was about 10% higher
- •Noradrenaline rises during fasting, supporting focus
- •Anecdotes include Unbroken prisoners' mental feats and Pythagoras requiring students to fast
Managing Hunger and Making Fasting Doable
Responding to Lewis's question about the hungry window, Fung explains that ghrelin peaks at habitual mealtimes and then falls, and that hunger largely vanishes after a couple of days. He offers practical strategies and stresses community support and the free nature of fasting, and Lewis shares his own four-day fast.
- •Ghrelin comes in waves tied to mealtimes and passes if you don't eat
- •Staying busy and drinking green tea or coffee help ride out hunger
- •In multi-day fasts, physical hunger almost disappears by days four to five
- •Supportive communities make fasting easier, as in religious fasts
- •Lewis describes losing seven and a half pounds on a four-day fast and feeling clear
Autophagy, Longevity, and the Benefits of Fasting
Fung explains autophagy as the body's recycling system, tied to a Nobel Prize, and says fasting raises growth hormone. Lewis then asks about industry incentives, and Fung gives his top benefits: free, flexible, simple, powerful, usable with any diet.
- •Autophagy breaks down old cell components so the body can rebuild
- •Growth hormone is about four times higher after a 24-hour fast
- •Fasting is historically the oldest dietary intervention
- •Lewis raises how businesses profit from selling more food and medicine
- •Fung's benefit list: free, combinable with any diet, flexible, simple, and the most powerful weight-loss tool
Type 2 Diabetes: Causes, Damage, and Reversal
Fung uses a sugar-bowl analogy to explain type 2 diabetes as too much sugar in the body, and says insulin drugs just push sugar back in. He says the disease is reversible through low-carb eating and intermittent fasting and describes its damage and prevalence.
- •Type 2 diabetes is overflow of stored sugar into the blood
- •Insulin and other drugs cram sugar back into the body rather than removing it
- •Reversal means not putting sugar in and letting the body burn it off
- •Roughly 10-15% have type 2 diabetes and 30-35% pre-diabetes
- •Complications include gangrene, kidney disease, blindness, heart attacks, strokes and cancer
Habits Over Willpower, Eating Six Times a Day, and Fruit
Fung argues that eating six small meals is a recipe for failure and that weight struggles are about habits and environment, not willpower. He promotes a supportive community through thefastingmethod.com, then discusses fruit versus added sugar.
- •Small frequent meals act like appetizers and make you hungrier
- •Offices and meetings full of food sabotage people's efforts
- •thefastingmethod.com offers community and tools
- •Fructose is the same wherever it comes from, but whole fruit has fiber and natural limits
- •If trying to lose weight, fruit should be limited, though it beats a cookie as a treat
Five Foods, Athletes and Fasting, and Fasting With Junk Food
Fung names the foods he would choose, including meat, fish, beans, avocado, cauliflower, broccoli and tofu. He then explains how fasting suits weekend athletes and off-season training but not high-level in-season athletes, and says both food quality and fasting matter.
- •His five-food answer centers on meat, fish, chicken, beans, avocado and above-ground vegetables, plus tofu
- •Fat adaptation takes several weeks of training
- •Elite athletes in season need calories and carbohydrates for performance
- •Off-season athletes may train in the fasted state and eat afterward
- •Fasting plus junk food beats junk all day, but food quality and fasting are separate levers
Toxins, Keto, Bulletproof Coffee, and How to Fast Long-Term
Fung dismisses the toxins-in-fat concern and defends keto as reasonable while noting its commercialization. He explains that bulletproof coffee only helps if it lets you fast longer, and says fasting should be a daily 12-14 hour cycle with occasional longer fasts, tied to longevity and growth versus repair.
- •Little evidence supports the toxins-stored-in-fat theory
- •Keto is not inherently unhealthy but can be hard to follow
- •Bulletproof coffee adds fat but not insulin response, so it only pays off if it extends the fast
- •Breakfast and petit déjeuner reflect built-in fasting
- •Longevity favors repair mode over growth mode, so eating less and fasting more as you age
Cold Exposure, Mindset, and Religion's Wisdom
Asked about cold therapy, Fung says he hasn't researched it but doesn't think cold explains the Inuit's low cancer rates. He says stress, gratitude and community likely matter though they are hard to study, and notes religions combine gathering, prayer, thanks and fasting.
- •Cold therapy may have promise but he hasn't looked into it
- •The Inuit still developed cancer after adopting processed foods despite the cold
- •Chronic stress and cortisol may weaken immune function
- •Gratitude and connection are hard to quantify, which is why they are rarely studied
- •Religious practices bundle community, prayer, gratitude and fasting
Resources, Three Truths, and Definition of Greatness
Lewis recaps Fung's books and website, then asks the three truths and greatness questions. Fung's truths are the feed-and-fast cycle, reversibility of type 2 diabetes, and staying real. He defines greatness as positively impacting people and offering new ways to understand problems.
- •Resources include The Cancer Code, The Obesity Code, The Diabetes Code, The Complete Guide to Fasting and thefastingmethod.com
- •Three truths: fasting as part of a cycle, type 2 diabetes is reversible, and stay real
- •Fung recommends doing real-world things over screen life and blocks haters
- •Greatness means impacting people positively and not tearing others down
- •His books aim to offer a new view of a problem instead of repeating the same advice
