Most people are told that “weight loss = calorie deficit.” But the truth is, a calorie
deficit is a myth. Your body is not a simple calculator where you just subtract
calories and lose fat. In this video, Dr. Jason Fung explains the science behind
why focusing only on calories fails, and why hormones, insulin, and fat
metabolism are the real keys to healthy and lasting weight loss.
When people try extreme dieting or drug-induced appetite suppression, they
often experience side effects like the dreaded “Ozempic face” — hollow cheeks,
sagging skin, and an unhealthy look. This happens because subcutaneous fat
(the fat under the skin) gets burned instead of visceral fat (the dangerous fat
around your organs). The result: you may lose weight, but you don’t look or feel
healthy.
Fasting works completely differently. Instead of just cutting calories, fasting
changes your hormones and metabolism:
�� Insulin drops, allowing fat burning to start
�� Growth hormone rises, protecting muscle and skin elasticity
�� Autophagy activates, repairing tissues and preventing loose skin
�� Visceral fat is targeted, which improves health and appearance
�� Brown fat (through beiging) is activated, boosting metabolism naturally
That’s why people who fast look healthier, stronger, and younger compared to
those who follow harsh calorie-restricted diets.
In this video you’ll discover:
✅ Why calorie restriction almost always fails
✅ The science of subcutaneous vs. visceral fat
✅ How fasting avoids the “Ozempic face” problem
✅ The role of hormones in fat burning and aging
✅ How fasting improves skin health, prevents sagging, and supports long-term
fat loss
�� If you’re serious about losing weight without losing your health or youthfu
look, this video is a must-watch.
�� Subscribe now for more science-backed videos on fasting, weight loss, an
metabolic health. And don’t forget to like ��, comment ��, and share this vid
with anyone who still believes in the calorie deficit myth!
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⏱️ Chapters / Timestamps
0:00 – Introduction: Why “calorie deficit” is a myth
1:10 – The calorie counting problem explained
2:30 – How calorie restriction affects your body
3:45 – Subcutaneous vs. visceral fat: which one really matters?
5:20 – Why fasting is different from dieting
6:40 – Hormonal impact: insulin, growth hormone & fat burning
8:00 – Fasting and skin health (no sagging, no hollow cheeks)
9:25 – Autophagy and natural skin tightening
10:45 – White fat vs. brown fat (the beiging effect)
11:50 – Key takeaway: Why calorie deficit cannot ever exist
=============================
�� BOOKS:
�� The Obesity Code – Reviewing underlying physiology of weight loss an
how low carb diets and fasting can help.
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disease and dietary strategies.
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�� YouTube Medical Lectures (for specialist physicians)
▶️ The Roots of the Obesity Epidemic: https: // • The Obesity Epidemic,
Explained
▶️ Therapeutic Fasting – The Two Compartment Problem:https: // •
Fasting and Weight Loss – Solving the…
▶️ Does Calorie Counting work?: • Why Calorie Counting rarely leads to
…
▶️ Two Big Lies of Type 2 Diabetes: • Two Big Lies about Type 2
Diabetes
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#Fasting #FastingMimickingDiet #DrJasonFung #WeightLoss
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Yes I did ,thank you ❤
Wait, where is the part aboput skin health, no sagging, no hollow cheeks and natural skin tightening????
What about for those who workout in the early mornings. I have done fasted and fed 5am workouts. I get lightheaded and feel like crap if I don't eat.
Intermittently fast on days I don't workout early?
if this was true when insulin is high, you would pass out and die
Wait, are you trying to suggest that people with insulin resistance are immune to starvation and the laws of thermodynamics? 🤦♀️
TIL: I just die on a hike a longer hike, if I have some snacks inbetween! Let's say a cube of sugar every 20 minutes.
One snack ==> Insuline spike
I might need 1000-1500 kcal for this hike… Where should the energy come from, if the fat is not accessible? Not from the fat, I just learned…. Fung just said that this isn't possible, because I snack.
Anyways guys… I'm ded now
Your video doesn't explain what happens if your energy output is high, but your caloric intake is low, while having high insulin. How does the equation balance? In order for the presentation to carry any validity, it must describe the reconciliation method in this scenario.
He says that if calories coming in are less than calories going out, "you must take the calories from storage or body fat out."
THAT IS LITERALLY HOW A CALORIE DEFICIT WORKS!
It is hard for me to loose weight doing fasting and low carb diet with exercise. I think, I still need to monitor my calories.
What about combining IF and lowering calories?
Wow ! this is the best explanation iv ever herd, you are a genius !
So your body is not in a caloric deficit, but your food intake should be to lose weight (assuming a healthy diet)
?
What a croc of shite.
This guys is delusional and obsessed with insulin.
Yes, insulin is important but if in the highly unlikely by event of using all your glycogen, then through gluconeogenesis, your body makes energy from non carbs through the liver and kidneys
If still energy is required then through lipolysis, it makes energy from fatty acids
Then if still needed, it goes to protein.
Thank you, thank you, thank you! ❤
8:57 "You can't store it when the insulin levels are low". Boom!💥
Eventually something is gonna give, either your body is eventually gonna break down the fat or you would die so I doubt your body is gonna let you die. May slow down your metabolism for a bit but eventually it’s gonna start breaking fat down because it has to have energy, if you start getting cold then you are burning less calories but then your body is gonna start shivering using more calories. Granted I don’t doubt that has a role especially once you break your bodies ability to use and regulate insulin but normally when it’s so broken from being so obese the amount of energy your body needs is thru the roof so calorie deficit is still needed in the end you basically don’t give your body an option to store and eventually it will have no choice but to start breaking down the fat
I’m so confused. There’s so much conflicting data out there. We can’t just eat a whole protein diet obviously so how much protein should we eat as not to release too much insulin? And how much carbs do we eat so as not to release too much insulin? And also what I’m hearing is there’s kind of no way to tap into your fat stores unless you fast?
I told an orthopedic surgeon about Dr Fung and he said, oh no, he will put me out of a job, I like obese people.
Altho the guy might have been kidding I think this truly reflects the attitude of many endocrinologists and bsristric surgeons.
I intend to educate my fellow health care practitioners, one person at a time.
I
I would eat below my BMR for most of the time and exercise moderately, mostly walking. I started doing this January 2025 and now in April 2026 I am 85 pounds lighter. What really helped is giving up all the processed foods and sugar and by doing so, I’m never hungry. The problem with most people is they say they wanna lose weight and feel healthier, but they don’t wanna give up processed foods and sugars and over eating. I have never drank alcohol, taking drugs or smoked ever in my life. Not too many people can say that nowadays.
Everybody still talking about calorie in calorie out like it’s the Bible
Good perspective it mean the whole calorie deficit discussion feel a bit less simple than people usually make it. I have noticed the same thing while using mycalsuite too, the small detail really matter.
After 60 years “ on a diet” I FINALLY understand. Dr. Fung you are a saint!! 🙏🏽🙏🏽🙏🏽
What a bunch of none sense. If you eat less than your daily TDEE you will lose weight and burn fat. No need for fasting. It's not rocket science. Calorie decicit does not exist? ok whatever you say dude.
Genuinely want to know; if eating too little over a period of time, wouldn’t the body adapt to needing less food and then lowering metabolism ?
Dr. Fung, thank you for your dedication to helping ALL of us gain/regain our health… and for FREE! Those of us on a fixed income need all the help we can get. I’m a disabled senior with multiple doctors; but with YOUR help via YouTube I am getting better. Your help has far surpassed the good intentions but stubborn
”knowledge” of my other doctors, as well intentioned as they are. Your fans all over the world love and appreciate you, Dr. Fung!❤
Yess!!!! Finally a good video.