The Science of Intermittent Fasting with Dr. Jason Fung (2024)

Can Athletes Use Intermittent Fasting?

Even if you don’t suffer from prediabetes or Type 2 diabetes, intermittent fasting has so many benefits to your overall health. In Dr. Jason’s new book, The Cancer Code, he explains how intermittent fasting can reduce your risk of cancer and other diseases!

But what if you’re an athlete, and you need a high-calorie diet to supplement all the exercise you’re doing? Can you still use intermittent fasting to upgrade your wellness? I asked Dr. Jason for his thoughts:

“You have to differentiate between the weekend athlete, the one who really isn’t at that super high level of competition, [and the professional athlete]. … So if you’re one of these guys who works out two or three times a week … [fasting] is perfectly acceptable because if you don’t eat, your body will simply take those calories that it needs from your body fat.” – Dr. Jason Fung

If you work out on a moderate level, intermittent fasting is not off limits! In fact, it will help you burn off fat at a more efficient level and make room to build muscle. However, if you’re an elite athlete, chances are that you need those calories.

“Most [elite athletes] don’t have enough body fat to sustain [that sort of fasting], right? … So what we do there, and we’ve worked with a number of elite athletes, is that you have to separate what you’re trying to do. So in the ‘on-season,’ you can’t really fast. It’s hard to do. You need too much energy.” – Dr. Jason Fung

Here’s the bottom line for athletes: It depends on your body type, your sport, and other health factors. As always, it’s important to talk to your doctor before trying intermittent fasting, especially if you’re a high-performance athlete!

Dr. Jason Fung’s Top Five Foods to Eat for a Healthier Life

Of course, intermittent fasting is not as powerful if you don’t eat the right foods in the first place! If your diet is composed solely of carbs and sugars, then the odds are intermittent fasting won’t give you the results you’re looking for. What you eat directly affects your mental, emotional, and physical health, so it’s important to get clear on what foods you should eat and what foods you should avoid.

Whenever I have health experts come on The School of Greatness, I love to ask them about their favorite foods for a healthy lifestyle and why they love them. I asked Dr. Jason this same question: “If you could only eat five foods, what would those be, based on your scientific research/benefits they have for the body?” Here are his answers:

#1. Meat

There’s a lot of debate on meat — both ethical and environmental — but from a nutritional point of view, Dr. Jason says that meat is one of the most nutritious foods out there.

“Fish and chicken for sure would be up there. And, you know, scientifically, of course, [meats are] much more complete sources of protein for us because we’re animals. So, therefore, we use animal proteins much better than we can use plant proteins.” – Dr. Jason Fung

If you’re not a meat-eater, don’t worry — there are many other foods that have nutritional benefits and proteins as well!

#2. Beans

If you’re a vegetarian, beans are a great source of protein to supplement your diet!

“People have eaten beans for … millennia — like [they’ve] subsisted on beans and so on. So that’d be a … vegetarian source of very good protein and can actually be quite delicious!” – Dr. Jason Fung

#3. Avocado

One of Dr. Jason’s favorite fruits is avocado!

“I think everybody loves avocado, and there are so many vitamins in there and so on.” – Dr. Jason Fung

In addition to having lots of vitamins, avocados also contain amino acids and help decrease the risk of diabetes, heart disease, and other health concerns.

#4. Cauliflower and Broccoli

If you’re looking to replace a carbohydrate side dish, look no further than cauliflower and broccoli! These two vegetables are rich in nutrients and are much better for your body than mashed potatoes or even rice!

#5. Tofu

Lastly, Dr. Jason said he loved tofu, and it’s a great vegetarian protein option as well! Tofu also contains a lot of amino acids and nutrients, such as potassium, iron, and manganese.

Remember: If you don’t supplement intermittent fasting with a healthy spread of foods, such as the ones above, it won’t have its full effect. To level up your health, it’s essential to look at it from a holistic standpoint so that you have everything working for you instead of against you!

How to Live Longer and Fuller: Go into Maintenance Mode

By eating healthy and not too often throughout the day, we increase our odds for a long, full life! Dr. Jason broke down the science for us in a way that everybody can understand:

“Our body has sort of two ways that it can go. You can either go into sort of growth mode or [you] can go into cell repair and maintenance mode. And the way you do that, of course, is by eating less, and fasting plays a big role in that. Because again, if you eat, then you’re going to activate the nutrient sensors. … If you’re young [or a kid], that’s fine. But think of it like a race car, right? You rev that engine, you’re going to go really fast, but you keep revving the engine, [and] it’s not going to last for very long, right? So you need to put that engine into sort of storage for a little while if you want to maximize the length of it.” – Dr. Jason Fung

I love the metaphors Dr. Jason uses. It makes total sense, right? Life isn’t a sprint — it’s a marathon, and to run it, we need endurance. Intermittent fasting helps us tap into that longevity. As Dr. Jason says, “We’re designed to eat until we’re full and then stop.” In our society today, it’s so easy to just keep eating and keep eating — just because the food is so readily available to us. But if we break up our meals with periods of fasting, we take our bodies back to that maintenance state.

“As you get older, you want to push yourself into that longevity stage, which means eating less, which means doing more fasting.” – Dr. Jason Fung

Another thing that helps us live longer is our mindset:

“So when people talk about positive attitudes and gratitude and community and staying connected and all that sort of stuff, it sounds hokey, but it actually has a huge impact on life and quality of life and even longevity.” – Dr. Jason Fung

It can be difficult to study the effects of mindset on health, but more and more people are noticing that those with healthier mindsets have healthier bodies. Dr. Jason explained that there are hormones released when you’re happy, and your immune system improves when you’re in a good mood!

“The immune system, which under chronic stress winds up getting degraded, right? … If you’re under too much stress, your immune system really doesn’t work as well. And the immune system plays a key role in fighting cancer.” – Dr. Jason Fung

If you can take care of your body, while also taking care of your mental and emotional state, you are much more likely to live a longer, fuller life!

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

This interview was extremely eye-opening for me — it’s full of so many great tools and valuable information that you can use to level-up your health and live a longer life!

I want to acknowledge Dr. Jason Fung for his amazing analogies — he turns the complex into something that is understandable and easy to break down. Cancer, obesity, and diabetes can be very hard to understand when you’re dealing with the sickness itself, but the fact that he is able to communicate effectively and simply is so powerful for the rest of us.

I also love Dr. Jason’s definition of greatness:

“I think, you know, that greatness is really about being able to impact people in a positive way. … to be able to impact somebody so that … they’ll be able to lose weight or they’ll be able to reverse their diabetes or understand cancer better as a disease. [Helping people] is a humongous privilege.” – Dr. Jason Fung

Dr. Jason lives by that definition, and he’s impacted so many people in such a healthy, positive way! I was honored to have him on the podcast for a two-part interview, and I know that I personally learned so much. Definitely check out Part One if you haven’t already!

If this interview impacted you, we would love to hear about it! Tag Dr. Jason, @drjasonfung, and me, @lewishowes, on Instagram with a screenshot of the episode and your greatest takeaways!

Remember: Your health isn’t out of your control. There are so many different things you can do to give yourself the upper advantage!

To Greatness,

The Science of Intermittent Fasting with Dr. Jason Fung (1)

The Science of Intermittent Fasting with Dr. Jason Fung (2024)

FAQs

Is there any real science behind intermittent fasting? ›

Studies discovered that intermittent fasting boosts working memory in animals and verbal memory in adult humans. Heart health. Intermittent fasting improved blood pressure and resting heart rates as well as other heart-related measurements.

What kind of diet does Dr. Fung recommend? ›

Dr. Fung recommends intermittent fasting and a low-carbohydrate or ketogenic diet to help people lose weight and manage diabetes. Fasting is when you restrict your intake of food and drink for a period of time.

Who is the best expert in intermittent fasting? ›

Jason Fung, MD, is a Toronto-based nephrologist and a world-leading expert in intermittent fasting and low-carb diets.

What is the most successful intermittent fasting? ›

Many people consider the 16/8 method the simplest and most sustainable form of IF — you might want to try this practice first. If you find it easy and feel good during the fast, then maybe try moving on to more advanced fasting methods. Another approach is to fast whenever it's convenient.

Why is 16 hours the magic number for fasting? ›

During the 16-hour fast, your body undergoes a process known as autophagy, a process where the body destroys old or damaged cells in the body. Autophagy recycles the cells that help in the reduction of inflammation in the body and reduces diseases.

Does coffee break intermittent fasting? ›

Technically speaking, eating or drinking any calories breaks a fast. That means it's generally considered OK to drink black, unsweetened coffee or tea, as well as water.

What can you drink while fasting Dr Fung? ›

Drink water, tea, coffee, or bone broth. That's it. And when you fast regularly, you do not need to feel guilty about enjoying one of life's little pleasures, because you can make up for it.

What is Jason Fung's fasting method? ›

If TRE is working for you, Jason Fung often suggests that you push it to 16 hours of not eating. This method is called 16/8 intermittent fasting. You eat during an 8-hour period, ideally before dark. This is the shortest fast that will significantly activate autophagy.

Can I drink chicken broth while intermittent fasting? ›

Broth. While broth will technically break your fast, it contains high levels of necessary sodium and other minerals, which helps your body replenish electrolytes and stay hydrated while also fighting off hunger pangs. 2 Most broths also contain very few calories (1/2 cup bone broth contains ~15 calories.)

What works better than intermittent fasting? ›

Reducing total calories may be more effective for weight loss than intermittent fasting | American Heart Association.

What foods won't break a fast? ›

Foods you can eat while fasting
  • Water. Plain or carbonated water contains no calories and will keep you hydrated during a fast.
  • Coffee and tea. These should mostly be consumed without added sugar, milk, or cream. ...
  • Diluted apple cider vinegar. ...
  • Healthy fats. ...
  • Bone broth.

How much weight can you lose in a month with intermittent fasting? ›

If you consistently stay active while following intermittent fasting, you can lose as much as 6-8 pounds per month. This estimation is shockingly high when you consider that all you have to do is not eat for select hours throughout the day.

Is it better to eat breakfast or dinner during intermittent fasting? ›

She says human metabolism works more efficiently in the morning, and suggests not skipping breakfast, eating dinner early and starting the fast at night time instead. “We are not meant to eat late in the night. It is against our body's circadian rhythm,” she says, referring to people's natural body clock.

How to lose belly fat by fasting? ›

Best Intermittent Fasting Method For Subcutaneous Belly Fat
  1. 16/8 Method: Fast for 16 hours and have an 8-hour eating window daily. ...
  2. 5:2 Method: With the 5:2 method, you consume your regular diet five days a week and consume around 500-600 calories for two remaining fasting days.
Jul 30, 2023

Is intermittent fasting actually effective? ›

Benefits of intermittent fasting

This causes an increase in substances called ketones. This, coupled with fewer calories consumed overall, can lead to weight loss. Research suggests that alternate-day fasting is about as effective as a typical low-calorie diet for weight loss.

What do doctors say about intermittent fasting? ›

Intermittent fasting is safe for many people, but it's not for everyone. Skipping meals may not be the best way to manage your weight if you're pregnant or breast-feeding. If you have kidney stones, gastroesophageal reflux, diabetes or other medical problems, talk with your doctor before starting intermittent fasting.

What is the scientific logic behind fasting? ›

Essentially, fasting cleanses our body of toxins and forces cells into processes that are not usually stimulated when a steady stream of fuel from food is always present. When we fast, the body does not have its usual access to glucose, forcing the cells to resort to other means and materials to produce energy.

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