New book from NYT bestselling author Lewis Howes is now available!

New book from NYT bestselling author Lewis Howes is now available!


Jason Fung

How To Prevent Cancer With Your Food & Fasting (Part 1)

Can we prevent cancer just by fasting?

Can we prevent cancer just by fasting?

Psychologist Anne Wilson Shaef said, “Good health is not something we can buy. However, it can be an extremely valuable savings account.” And Deepak Chopra said, “Whether we realize it or not, all of us are responsible for creating the body we live in.”

Diseases like diabetes, obesity, and cancer are increasingly dangerous forces in the world today. Millions of lives are affected by these illnesses every day, and while we do have some useful treatments, we’re a long way from finding cures. It seems like it may be time to think outside the box.

My guest today is physician, author, and researcher Dr. Jason Fung. He’s known for writing groundbreaking science-based books about diabetes and obesity, The Diabetes Code, The Obesity Code, and The Complete Guide to Fasting, where he’s challenged the conventional wisdom that diabetes should be treated with insulin. He’s also the co-founder of The Fasting Method, which is a program to help people lose weight and reverse Type 2 diabetes naturally with fasting.

You read that right — fasting. The path to preventing diabetes, obesity, and even cancer may be as simple as that!

In today’s episode, Dr. Jason and I dive deep into some topics discussed in his new book, The Cancer Code, to learn the science behind the disease and how our diet and fasting can play a role in managing and even preventing us from getting cancer. 

We had such an incredible conversation that I just had to split this interview into two parts! You’re definitely going to want to stick around for Part Two on Wednesday — Dr. Jason is bringing the science, wisdom, and inspiration we need to take control of our health. 

Who Is Dr. Jason Fung? 

Dr. Jason Fung, MD, is a Toronto-based nephrologist and a world-leading expert in intermittent fasting and low-carb diets. He is also the bestselling author of The Diabetes Code, The Obesity Code, and The Complete Guide to Fasting, and the creator of the Intensive Dietary Management program as well as co-founder of The Fasting Method.

After graduating from the University of Toronto and completing his residency at the University of California, Los Angeles, Dr. Jason returned to Toronto to work as a kidney specialist. He began to work with patients to prevent and treat Type 2 diabetes and obesity — both precursors to kidney disease. He started by prescribing more conventional solutions — low-fat, low-calorie diet, and exercise — but he found that such conventional treatment plans weren’t truly helping his patients lose weight and get healthier. That’s when he decided to think a little outside the box.

Dr. Jason, along with his friend and professional partner, Megan Ramos, co-founded the Intensive Dietary Management program and The Fasting Method to help their patients truly lose weight, prevent obesity and Type 2 diabetes, and completely avoid kidney disease. They started seeing real results in their patients, and now, they’re beginning to see that fasting can also lower our chances of getting cancer.

Dr. Jason fundamentally believes in the power of intermittent fasting to help people lose weight, lower their blood glucose levels, reduce their medication dependency, and improve their overall health. His work is positively impacting thousands of people around the world, and today, he’s sharing his wisdom and knowledge right here on The School of Greatness!

The Main Causes of Cancer 

Dr. Jason and I kicked off our interview by discussing the causes of cancer and how we can decrease our likelihood of developing cancer. Even though there is still some mystery surrounding cancer and its causes, we do know a lot about the disease. 

“Things that cause cancer are called carcinogens, and the World Health Organization maintains a huge list of these carcinogens. … A couple of studies have looked at the sort of percentage contribution of these carcinogens to cancer, and the biggest one, of course, is tobacco smoke. … Interestingly, the second biggest and almost as big [cause] is actually our diet.” – Dr. Jason Fung 

Many carcinogens play a role in developing cancer, but tobacco smoke is the most common and the most widely known. Even though smoking usage has greatly declined over the years, tobacco smoke still contributes to 35% of all cancer cases. We’re all very familiar with the risk of smoking, but the fact that our diets can contribute to cancer is less widely known. Dr. Jason stated that obesity is a major contributor to cancer: 

“It became sort of more and more clear that this cancer is actually an obesity-related disease. … We had this obesity epidemic, so it became a bigger and bigger problem. And in 2003, when they started to look at the studies, that was the first really definitive studies that said, ‘Hey, obesity is actually a huge risk factor as well as Type 2 diabetes.’ And both of those conditions will actually increase your risk of certain types of cancer. … The World Health Organization considers 13 different types of cancer as obesity-related cancers.” – Dr. Jason Fung

With the obesity epidemic becoming rampant in the past couple of decades, cancer cases have also increased. Obesity increases your likelihood of developing several cancers, including breast, colorectal, liver, ovarian, prostate, and many others. 

So what can we do to decrease our risk of cancer? 

“If you can maintain a normal weight, you’re going to reduce [your chances of cancer.] Just like stopping smoking, right? You’re going to reduce your risk of these types of cancer.” – Dr. Jason Fung

Maintaining a healthy weight decreases your likelihood of developing many kinds of cancer. That all being said, Dr. Jason noted that many other factors contribute to cancer, including sun exposure, radiation, other carcinogens, and even genetics. It may sound like a terrifying prospect that you may be biologically predisposed to develop cancer, but you can still take precautions to prevent it. 

“Cancer is like a seed. So if you have other genetics, you have the propensity to develop cancer. And this seed of cancer actually exists in all of ourselves. … What’s important then is you can’t do anything about the seed, but what you can do something about is the soil, which is that if you provide a fertile sort of soil for that seed to germinate, then you are going to increase your risk of developing this cancer. And cancer is not a rare disease. … So it’s something that we really have to think about as we live longer.” – Dr. Jason Fung

Even though you may be genetically inclined to develop cancer doesn’t mean that you are doomed to develop it. You can live a lifestyle that will decrease your chances of developing the disease! 

“Once you actually develop the cancer, then it’s really hard to fix from a diet standpoint. You really need the drugs that we’ve spent millions and billions of dollars developing over these last 30 years. But in terms of preventing cancer, there’s actually no reason why you couldn’t.” – Dr. Jason Fung

We can take dietary steps to protect ourselves from developing cancer. Dr. Jason advised that we significantly lower our sugar intake and avoid refined foods — especially refined carbohydrates. There’s an abundance of evidence supporting the fact that the types of food we consume contribute to cancer. There are several groups of people that were once thought to be immune from cancer, including Inuits and some people groups in Africa, but in reality, it was due to dietary reasons rather than genetics.

“The people who live traditionally in Africa get no cancer, no colon cancer, but the minute they transitioned to a Western-style civilization with their foods … they actually start to get cancer.” – Dr. Jason Fung

Taking dietary precautions can decrease your likelihood of developing cancer, but the frequency in which you eat also plays a key role in preventing cancer. 

“Eating all the time provides that sort of fertile soil. So to understand why this is, you have to get back to sort of how cancer develops. So you have to understand that cancer … evolves almost as a separate species from us. … It grows or doesn’t grow depending on growth factors.” – Dr. Jason Fung

The frequency in which we eat affects the growth of cancer cells. Dr. Jason stated that when we eat throughout the day, we’re triggering growth signals to grow cells, and that includes cancer cells: 

“If you eat six, eight times a day, you’re telling your body [and] your cells in your body to grow. … If you don’t eat at all, what you’re going to do is shut down those growth signals and the cancer will have a difficult time to grow.” – Dr. Jason Fung

How frequently do you eat throughout the day? Do you only eat three meals, or do you snack as well? According to Dr. Jason, reducing the number of times we eat throughout the day can decrease our likelihood of developing cancer and keep us healthier. 

“The secret to managing our health is not more surgery or more medicine, it’s less.” @drjasonfung  

The Science Behind Intermittent Fasting

Contrary to popular belief, eating throughout the day is not good for your body. Your body is built to experience both a fed and a fasting state. Dr. Jason explained the process that occurs when your body is experiencing the different states: 

“You’re either in the fed state, or you’re in the fasted state. So when you’re in the fed state, you’re eating [and your] insulin is going up, and as insulin goes up, it’s normal job is to tell your body to store those calories. … Any time you don’t eat is called fasting. So when you fast, that means your insulin is gonna drop, and that’s the signal for your body to now start pulling those calories out of storage. … The only way that you can actually use the body fat is to let the insulin fall and not eat.” – Dr. Jason Fung

Our bodies store calories during our fed state and then use those stored calories during our fasting state. Dr. Jason warns that the high frequency in which the average American eats results in people no longer entering a fasting state for long enough periods of time. 

“Now, if you look at studies, the average duration of how long people eat for is about 14 hours and 45 minutes. That’s the average. So if you start eating at 8:00 AM, you don’t stop till 10:45 PM. … It takes about four hours to switch over into the fasting state.” – Dr. Jason Fung

The 14-hour duration in which someone consumes food doesn’t mean that they’re consistently eating, but they’re eating in regular enough intervals that their bodies cannot enter a fasting state throughout the day. Because their bodies can’t enter a fasting state, their insulin stays high, and they can’t burn stored calories. Eating too frequently is a major contributing factor for obesity, diabetes, and cancer. So what can we do to address this common problem and burn off excess fat? 

“It’s simple. Increase the amount of time that you’re not eating. And that’s all intermittent fasting is. If you eat one meal a day, for example, or if you [fast] within an eight-hour window or a four-hour window or whatever, what you’re doing is you’re simply allowing your body to use the calories that have been stored, which is body fat predominantly. That is precisely the reason you carry body fat.” – Dr. Jason Fung

Our bodies are designed to go through periods of fasting. Our extra body fat is there to supply us with calories during periods in which food is not available. Every pound of fat is worth 3,500 calories, and the average person burns 1,800 calories a day, meaning that if you were to not eat for a day and you had the average metabolic rate, you would burn off a one-half pound of fat. 

Dr. Jason regularly goes through periods of fasting. He frequently will go a full 24 hours without eating, and he sometimes will even not eat for days at a time. Fasting is actually a more effective way to lose weight than altering your diet. If you reduce your caloric intake, your body will then use fewer calories: 

“Metabolic rate is the amount of energy that your body uses in a day. [If] you cut 500 calories a day, then your body quickly reduces the amount of calories it uses by about 500 calories. So now you’re actually not losing any weight. … It stops burning the calories by reducing its metabolic rate.” – Dr. Jason Fung

Dr. Jason suggests that fasting is more effective for losing weight than reducing your caloric intake. When you fast, your body actually burns more than the average 1,800 calories per day.

“Instead of using food as your fuel, they’re switching it into body fat. … They did a study, for example, where they took people and fasted them for four days and measured how many calories they’re using. … They measured it at four days of zero food, and they were burning 10% more calories than they were per day than they were when they were eating. … You’re doing more work. Your body is actually not shutting down. It’s revving itself up.” – Dr. Jason Fung

Fasting is a surprisingly effective method of losing weight. It’s also incredibly simple and a whole lot cheaper than a diet plan. Have you ever tried intermittent fasting? The idea may sound strange to us, but different societies have practiced fasting throughout history. Millions of people still fast during religious holidays, such as Ramadan and Yom Kippur.

I actually had the pleasure of experiencing a four-day fast a couple of months ago, and I had a surprisingly positive experience. I felt healthier, looked younger, and I even lost seven and a half pounds! Even though intermittent fasting can benefit some individuals, it may not be for you. Consult your doctor before engaging in intermittent fasting, and definitely don’t do it if you’re already underweight. 

How Fasting Can Improve Your Life

Your body experiences many benefits when you fast! Dr. Jason noted that you become mentally sharper when you’re fasting:

“Your concentration is actually much higher when you don’t eat. … Our level of concentration, our mental ability, [and] mental agility [go] up significantly when we’re hungry.” – Dr. Jason Fung.

Dr. Jason told the story of Louis Zamperini — the subject of the book Unbroken — and his experiences as a prisoner of war in Japan. He and the other P.O.W.s experienced a heightened mental state because they were starving. One of the prisoners was able to re-read a book from memory, and another one learned Norwegian in a week. 

In addition to mental clarity, fasting also causes our hunger actually to decrease:

“They’ve done studies where they fast people for 24 hours and they measure a hormone called ghrelin, which is the hunger hormone. The higher it is, the hungrier you are. It turns out that our ghrelin peaks three times a day, breakfast, lunch, and dinner. … Ghrelin actually peaks, and then it just falls. If you don’t eat, it will actually just fall down … within a couple of hours right to baseline. … If you look at multiple day studies where they fast people for three, four, [or] five days, the ghrelin peaks, and then after about two days, it starts going down. … As you get to day four [or] day five, the hunger almost completely disappears.” – Dr. Jason Fung 

Even though you might think that your hunger would increase as days pass without eating, the reverse is actually true — your hunger decreases after days without food. 

Another benefit of fasting is a process called autophagy. Dr. Jason explained the process and why it’s so important for our health: 

“Your body breaks down these sort of subcellular organelles and just gets rid of them. It breaks it down and recycles them. The first thing you need to do whenever you want to renovate … is throw out everything in there, right? … So your body works the same way. The first thing you have to do is get rid of the junky old protein. … This is the body’s intracellular recycling system. … Flush it out and rebuild it into new stuff. … So all the cells in your body undergo this process of regeneration that you’re not going to get if you are eating all the time.” – Dr. Jason Fung

When we fast, our body starts breaking down our old proteins and cells in order to regenerate. Fasting is conducive for this process because fasting activates growth hormones: 

“One of the things that activates during a fasting is actually growth hormone. So if you fast for 24 hours, your growth hormone level is [around] four times what it is when you’re eating. … Why would [your] growth hormone [go] up? Well, it’s because of this whole process where you want to break down stuff.” – Dr. Jason Fung

When you go a full day without eating, you activate your growth hormone, resulting in autophagy, which regenerates cells and proteins. Earlier, we discussed how cell growth is harmful for our health, but our growth hormones don’t grow our cells they regenerate them. Fasting has many physiological and mental benefits that can keep us healthy and optimize us on our journey to greatness! 

Why You Should Listen to This Dr. Jason Fung Podcast Right Now… 

Guys, I learned so many fascinating things from Dr. Jason Fung, but the lesson isn’t over yet! Make sure to check out Part Two of my interview with Dr. Jason here. In part two, we’re talking all about the types of foods that you should be eating to live longer and how to reverse Type 2 diabetes, so you’re not going to want to miss it!

I want to share with you a final word from Dr. Jason on the importance of fasting and how it can truly change your life:

“[Fasting is] such an incredible tool that we’ve just sort of forgotten about, and yet has more power than almost anything else to prevent all of the diseases. And we don’t have to charge anybody anything. We’re not trying to sell anybody anything. We’re just trying to tell you, ‘Yes, you can [fast].’ Because if you have too much weight and it’s putting you at risk of this cancer, let your body burn off that sugar, [and] let your body burn off that fat.” – Dr. Jason Fung

Friends, join me on Episode 1,030 to learn all about the main causes of cancer and how you can avoid it, the science behind fasting, and the many other benefits of fasting. It will completely change your outlook on health and diet!

To Greatness, 

Lewis Howes - Signature

Some Questions I Ask:

  • What are the main causes of cancer?
  • What are the biggest benefits of fasting?
  • Can we reverse cancer? 
  • What does snacking do to our brain and digestive system?
  • What are the biggest myths about fasting?
  • Are supplements and vitamins actually bad for us?

In this episode, you will learn:

  • How to decrease your risk of cancer.
  • Why fasting is more accessible than you think.
  • Why we shouldn’t snack all the time.
  • The foods to cut to decrease your risk of cancer.
  • The advantages of starving.
  • The biggest myths around fasting to lose weight.
  • Plus much more…

Show Notes:

Connect with
Jason Fung

Transcript of this Episode

Music Credits:

Music Credit:

Kaibu by Killercats

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