Dr. Jason Fung Talks about Fighting Insulin Resistance

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Will fasting help a healthy person live longer? What are the keys to a successful fast? Do we know the actual differences between time-restricted feeding, intermittent fasting, and dietary restrictions and how they can be used to attack the root cause of Type 2 D metabolic syndrome and obesity? What is hyper-insulinemia? And why is it a problem?

Jason Fung, nephrologist and best-selling author, shares his experience utilizing an individualized approach to fasting, to successfully treat thousands of overweight metabolically ill and diabetic patients. Being a doctor who specializes in kidney disease gives him a unique insight into early indications of metabolic disease. Let’s listen to Dr. Jason Fung:


The normal action of insulin is to store food energy, that is, when we eat insulin goes up and we store it as food energy. We store it as glycogen in the liver or body fat, so we store food energy as either sugar or fat.

When you eat insulin goes up and tells the body to store food energy. At the same time, it also tells the cells of the body to use the circulating glucose because there is lots of food energy coming on so the liver, the heart, the kidneys, the skin, and the muscles; they don’t need to draw down their resource, they should use the food energy that is coming in.

So when insulin goes up, the glucose that is in the blood goes into the muscle cell, for example, so what insulin resistance refers to is the fact that for a given amount of insulin, that glucose is not going into the muscle cells. And the question is why?

What we know is that this is caused by fatty deposits within the liver and the muscles. So fatty liver and also fatty muscle, basically streaks of fat in the muscle. There’s not supposed to be fat in the liver and there is not supposed to be fat in the muscle, but you see it. When you see that, you know you have insulin resistance. The question is what causes it to accumulate. Dietary fat doesn’t go through the liver at all, it goes through the intestine where it is absorbed directly, but it gets absorbed as something called chylomicrons, which go through the lymphatic system, which then gets picked up through the fat cells. So dietary fat gets stored almost directly and doesn’t go through the liver.

Eating fat doesn’t cause fat accumulation, what about eating carbohydrates?

Carbohydrates are completely different. Carbohydrates are absorbed by the intestines and then they go through the liver, and the liver will store it as glycogen. But when those glycogen stores are full, you still have extra glucose molecules that you cannot store any further. So the liver begins a process called Novo lipogenesis. Essentially the liver takes the glucose and the protein packages into new fat and sends it out into the blood where it should be taken up by the fat cells. However, if you stimulate it too much and it is making too much of this fat, then it starts to accumulate in places where it should not, and you see it accumulating in the organs, in the fatty liver, in the muscles as well as the pancreas.

Experimentally you can do this with humans. You simply overfeed them carbohydrates.  One example is a study where they took normal people and they gave them a thousand calories extra, that is on top of their usual diet and they gave them very carbohydrate-rich food (So sugary food, snacks, some candies, some sodas, and some snacks). So demonstrating very clearly excess carbohydrates is the key determinant of this. You see the fatty muscle problem very clearly in cattle. Cattle are herbivores who normally eat grass. So they don’t eat that great. When you want to have marbling of beef, you want the streaks of fat that you get within the muscle that make the steak sort of very delicious. Mmm steak fat.

Kobe beef, for example, the Japanese delicacy which is very expensive, has a lot of this fatty muscle, and the thing to understand is how you get that. Cattle ranchers understand really well that you give refined grains to these cattle. Same thing in the fatty liver.
If you look at duck, when they make foie gras, what they do is they shove a tube into the duck or the goose and they force feed it very high starch mash. So it is the carbs which drives the accumulation of this fat inside the muscle cells and inside the livers, it is not the dietary fat.

As you develop this excess energy, as you are storing all this fat inside the muscle, your muscles, which normally takes in the glucose, are jammed full , then it is packed. Muscle cells are functional tissue, so fat cells should store fat, the liver and the muscle cells shouldn’t be storing fat. But when the liver and muscle cell is packed, and you are trying to put in more glucose, it simply can’t go in. What you see on the outside is that the glucose is not going into the cell, under the influence of insulin. You call this insulin resistance. It is not a problem with insulin receptors, not a problem with the insulin, the problem is that the liver cell, is already full of sugar and fat, and you can’t jam anymore sugar into that cell. That is what insulin resistance is, it is an overflow problem. Once you understand that you see that the solution is not to give more insulin, which is the solution our body comes up with. It doesn’t like the extra glucose in our blood, so it increases the insulin to jam it further into our tissues, but the tissues are already full. When that doesn’t work, you go to your doctor, and your doctor gives you insulin to jam it in and that ultimately is self-defeating as well.

The solution to the problem (which is that the cells are simply full) is to empty those cells. It is like a suitcase, if you put something into the suitcase, at first everything goes in nice and easy, but once it is full, you can’t jam those last two t-shirts. It is like the same t-shirts that you packed before and the suitcase you used before, but you can’t anymore because it is full. That is resistance, and that is what insulin resistance is. You are trying to put glucose into a cell that cannot accept any more.

Insulin resistance is completely reversible, and it only depends on two things; one-stop putting glucose into that cell and two-burn it all off, get rid of all the clothes in the suitcase, and then you can put some more in.
Insulin resistance itself is a process that developed over many years and probably many decades.

So how long does it take to reverse insulin resistance then?
If you think that you can reverse that process in a couple of months, you are likely mistaken. If you think about it that suitcase is completely full and it’s in fact well past the point where it should be. Are you willing to do get it all the way back down to normal? That takes a lot of fasting, a lot of strict dietary compliance over multiple decades.

Is it possible?

It is absolutely possible but it takes time and effort. But in the end, it is reversible. The important thing is to understand that it is reversible. It has taken decades to develop, so sometimes it takes years and decades to resolve itself. If you go back to the diet that gave you insulin resistance, that is highly refined carbohydrates, high sugar, high fructose , then you will develop it again. That doesn’t mean the treatment isn’t correct. Just like the suitcase, taking clothes out of that suitcase is the proper treatment and that’s why some people say, “wow this is a chronic problem, it can never be cured”. That is not the case, it is just the matter of whether you are willing to put in the amount of time it takes to reverse this condition.

So if we could take one step, just do one thing, to start reversing insulin resistance, what would you suggest?

We keep making it easier and easier for people to eat sugar, and glucose, and fructose. We have made high fructose corn syrup very cheap, we’ve put it in all of our foods, and I think that is one of the major problems. I think fructose is far worse than glucose. It is a sugar that is not metabolized by anything other than the liver. As opposed to glucose which is metabolized by all cells of the body. If you eat rice for example, or potatoes, that is mostly glucose. When you eat sugar, it is half glucose and half fructose, and fructose is many times worse, in causing the real problems of insulin resistance. So if you are going to severely restrict one thing, it should be sugar and high fructose corn syrup.

What we are talking about here is really a difference between fasting and calorie restrictions. A lot of people ask the question, well suppose I fast for 23 and half hours, I only eat one meal in 24 hours. And during that meal I eat 1000 calories? Well isn’t that just a caloric restrictions of 1000 calories, if you go from 2000 calories to 1000 calories isn’t that the same thing?

The answer is no, it is a completely different thing. The whole point of calorie restrictions is to limit calories, and the point of fasting is to reduce insulin. They have completely different purposes in mind and to understand it a little bit further, we have to look into a bit of physiology. Remember that when you eat almost any food, unless you are eating pure fat, your insulin goes up. When your insulin goes up, you tell your body to store food energy. Insulin tells fat cells to take up glucose and fat from your blood, it also tells fat cells to stop releasing fat into the blood. It tells muscle cells to take up blood glucose, and to stop burning fat.

Suppose that you take your thousand calories that you are going to eat and spread them evenly throughout fifty meals eating constantly, all day. Every time you eat a little bit, your insulin goes up.  Your body goes into fat storage mode because it can’t burn the fat. Technically, the insulin inhibits lipolysis, because your body wants to store energy, because that’s the instructions that insulin gives it. So as you store energy you get over thousand calories a day, you’re not able to use any of your fat storage, because you have kept your insulin high.
Therefore what happens is that your body only has a thousand calories over that day to spend, because that is all that came from food and your body has no access to your fat stores. So your body’s metabolism slows down to a thousand calories because you don’t have any more, you have thousand coming from food, because you are eating all the time and eating high insulin food. you have completely stopped access to your fat stores. And that is why metabolism slows down on a calorie restricted diet.
Fat is very high in calories, so these diets tend to also be low fat. Low fat means high carbohydrates, that mean high insulin, that means your body can’t burn its own fat, so it turns down the thermostat to conserve energy.

So that is what happens during calorie restrictions and that is what we have proven over the last 100 years. And the reason that we make this crucial error is because we don’t understand that this is sort of a two compartment problem. So I sometimes use that analogy in reference to glycogen vs body fat. But it also equally applies to when you are talking about food and stored food which is both glycogen and fat.
You can either go for food or stored food, which is the two different compartments. We often think of calories as a single compartment problem, that all calories go into a single sink and all calories come out of a single sink, and it is running at the same time, sort of like a giant one compartment sink. But that is not really the way it works. There are two compartments that you can access for food energy. One of these compartments is the energy that comes from the food that you eat. The other compartment is the food that you have stored in your body, which is either glycogen, which is how the body stores glucose, or body fat. The twist is we can only use one of these energy sources at a time.

And guess what the switch is?

That is what insulin does, it switches your metabolism. If you look at constant caloric restriction, that’s the problem. When you do intermittent fasting, it is completely different. Say you take that thousand calories of food energy, and now what you do is take it all in a single meal. So for 22 hours of the day your insulin is low, and for 2 hours of the day, immediately after eating, your insulin is quite high. This is the way the body works, hormones are normally volatile they’re not constantly high.

So what happens is that as you eat the one meal of the day, your insulin goes high, you store body fat, but because your insulin drops after your meal after 9-10 hour, it is a signal to burn the food energy that is stored.
So now you are starting to pull out glycogen from your liver, and if you don’t have stores in your liver, you will burn body fat.

But that is all in the category of stored food energy; that is the way your body stores food energy. Now over the 24 hrs, what happens is that you switch from burning food to burning food energy that is stored. You get thousand calories from food and you can take thousand calories from body fat. Your basal metabolism which wants to burn two thousand calories stays high, body temperature stays high, energy etc,

Imagine you have a railroad, and imagine the railroad switch.

Your body can either go on one track or the other, and there is a switch to change tracks. But the train cannot take two tracks at the same time.  Remember the two tracks are two sources of energy, one is the food you eat, and the other is energy stored in your body in the form of glycogen and body fat. Physiologically, it is a completely different situation, between constant calorie restriction and a situation with intermittent fasting.
This is the reason why obesity is really a time-dependant problem, because persistently high levels of insulin, over long periods of time, are going to lead to insulin resistance. This will develop over many, many years perhaps decades. The problem with insulin resistance is that it will stimulate the body by producing more insulin. If your insulin stays that high all the time, then you are going to drive the body to block off the fat stores. And therefore you are going to only be able to use the food energy. And this is the reason why people who have been overweight for many years, find it harder to lose weight. If you have been obese for two months, that weight will generally fall right off, if you apply yourself and get rid of it. If you have the weight for 20 years, it will be much harder to get rid of.

If being insulin resistant makes it harder to lose weight, what does that imply for children?

The situation is that a lot of children are now becoming obese, and this will be a problem later. When they get to middle age, they will have more trouble getting it off, than if they hadn’t had the problem until mid thirties. This is why childhood obesity is such a problem, and it will be a bigger problem in the future. Because when you become insulin resistant, that is going to lead to high insulin levels, which will lead to more weight gain and then more insulin resistance.  So you need to break that cycle, and one of the way to do it is through fasting.

A good friend of mine, whose sugar was over 600, told me he couldn’t go low carb, because it was hard on his kidneys. And his kidney levels were abnormal. Likewise when I was a kid I was told, a low carb diet works, but the long term effect of it on the kidneys was unknown. That was enough to scare me away from low-carb for a long time. What are the effects of low carb diets on the kidney?

One of the questions we get is about chronic kidney diseases. I am a kidney specialist and have been one for 20 years. This question has been looked at in fairly extensive detail, but, nevertheless, is one of the big concerns. So let’s go back and see what the problem is. We often recommend people with chronic kidney disease to avoid high-protein diets. There are a lot of theoretical reasons why we do so. For example, dietary proteins create a lot of waste products. To use excess amino acids for energy, we need to turn them into carbs.  So we need to remove the atoms that are not carbon, hydrogen, and oxygen. Amino acids all have amine groups containing nitrogen. So one of the steps in this process is to de-aminate the molecule by removing the nitrogen atom inside a molecule of ammonia. Now, ammonia is toxic so you need to turn it into urea, and filter it out of circulation into urine to be excreted from the body. Nitrogenous waste products are not flushed out if your kidneys are not working properly. There is also a concern if you eat a lot of protein-rich animal foods, you may acidify your blood a little bit and if your kidneys aren’t working, they can’t neutralize the acid. But keep in mind that these are all theoretical concerns.
Many years ago, we did a large randomized control trial called the MDRD study. This looked at the question of people who have existing kidney disease, whether or not eating low-protein diet is beneficial. And the answer was surprising, as it made very little difference between a normal protein diet and low protein diet. General recommendations for people is to eat somewhere around 0.8 to 1 gram per kilogram of lean mass. And once again you have to realize that this is not the total weight of the food, it is the sort of protein weight, to which you have to make some adjustments. These issues must be kept in mind.

Where did this recommended daily intake of protein originate from?

The way that they came to this number was that in the 50s and 60s, they were trying to determine the daily amount of food you must take. At the time, they did not know how much protein people should or should not be eating. If you look across nations, there are some nations that eat a lot of protein, and some nations that eat very little protein. Some are predominantly vegetarian, eating a lot of carbs. Others like the United States eat a lot of protein. So what they decided to do for all nutrients, they took a sample of people, healthy Americans, and they recorded what foods they were eating and they decided that the average for protein was 0.6 grams per kilo. Keeping in mind, people were normal and healthy at 0.6, they added it to standard deviations. It is hard to eat too much protein, and since the wanted to make sure that everybody eats adequate protein, so they put it at 0.8 grams per kilogram.
That was a level of protein 90% of Americans were not eating. They said, “well you should try and eat 0.8” with the idea that it is better to eat too much than too little protein. That is how our daily recommended protein became 0.8 to 1 gram depending on whom you ask and so on.

This has since been experimentally shown in nitrogen balance studies, and summarized in the meta-analysis from Randatel 2003 entitled ‘meta analysis of nitrogen balance studies for estimating protein requirements in healthy adults’. They found that people were able to remain in nitrogen balance between 0.3 and 1.0 grams per kilogram of body weight, with an estimated average requirement of 0.65 grams per kilogram and a recommended daily intake of 0.83 grams to be adequate for 97.5 % of people. It’s not very far off from what an average American might eat, again if they eat a lot of meat, it is higher, if they don’t, it is perhaps lower.

When I started my low carb journey, my doctor told me and I am quoting here,” I have seen patients absolutely wreck themselves on a low carb diet”. She was talking about complications from over consuming protein. So where did the idea that low carb meant high protein come from?

What happened was that during the Atkins diet phase, it was very much a low carb proponent. But at the time in the 70’s to 90’s, there was this huge sort of anti-fat message. This hysteria that fat was really, really bad for you. So even though Atkins was a low carbohydrate proponent, when it got mixed with low fat message, there was this spike in the idea of a super high protein diet, where you should eat instead of 0.8 grams per kilo, 3-4 grams per kilo of protein. It is not to say that you can’t do well eating that much protein, everybody is different and some might not do well. You don’t need to eat that much.

When you start going into artificial foods like whey protein concentrates, and creatine powders and so on, you can get into trouble because now you are entering artificial situations. You are moving from the core message which is to eat real food. This became clear when they analyzed large populations, they looked at people who had normal kidney disease. Kidney disease has 5 stages- 1 being normal and 5 being worst dialysis. They look whether high protein diets actually cause kidney disease. The answer is a clear no. Your body has the ability to excrete that excess protein if it doesn’t need it. It doesn’t cause kidney disease. 
If you have kidney disease, we know from the MDRD study that eating a lot of protein doesn’t really make the kidney disease get worse faster. They weren’t eating the super high 1.5-2 grams of protein per kilogram a day; they were eating 0.8 to 1 gram per day. One of the big changes when we get to ketogenic diet from a sort of standard Atkins diet, a sort of modified Atkins diet became low carb and low fat for a little while thinking “oh let’s just eat a ton of protein”. Then the ketogenic diet during the last few years was more towards high fat just to contrast itself with the low fat. It is not artificial fat we are talking about, we are talking about high-end natural fats.

So does protein cause kidney disease?

If you don’t have kidney disease it doesn’t cause it, if you do have kidney disease it doesn’t make it worse. So no, you don’t have to worry about eating too much protein as long as you are sticking to real foods. On the other hand, this sort of diets that I recommend tend to be moderate in protein, that is still sticking to around 0.8 grams per kilo per day, cutting down the carbohydrates and replacing that with natural fats.

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