Why Fructose causes insulin resistance | Insulin Resistance | Jason Fung

Summary

This video explores the detrimental effects of sugar, particularly fructose, on weight gain and type 2 diabetes. Unlike glucose, which is utilized by all body cells, fructose is exclusively metabolized by the liver, leading to fat production and contributing to fatty liver, insulin resistance, and metabolic syndrome. The script highlights studies showing the correlation between sugar-sweetened beverages and increased risk of weight gain and type 2 diabetes, emphasizing the importance of reducing sugary foods and beverages in weight loss and diabetes management.

Takeaways

• 🍬 Sugar, particularly in the form of sucrose (table sugar), is more harmful than other carbohydrates due to its composition of glucose and fructose.
• 🔍 Different types of sugars, such as glucose, fructose, and lactose, have distinct impacts on the body, with fructose being especially concerning for health.
• 📈 High consumption of sugar-sweetened beverages has been linked to increased weight gain and a higher risk of developing type 2 diabetes.
• 🚫 Fructose does not raise blood glucose levels, which previously led to the misconception that it was a healthier alternative to glucose.
• 🍇 Fructose is naturally found in fruits and was once considered healthy, but recent studies have shown its negative effects on the body.
• 🧬 The metabolism of fructose is unique as it is primarily processed by the liver, unlike glucose which can be used by nearly every cell in the body.
• 💉 Excessive fructose intake can lead to the development of fatty liver, which in turn causes insulin resistance and increases the risk of type 2 diabetes.
• 📉 Studies have shown that fructose consumption can worsen insulin resistance by up to 25% compared to glucose.
• 🍞 Low carbohydrate diets can be effective for managing type 2 diabetes as they replace glucose with fats and proteins.
• 🍎 While fruits contain fructose, they should be consumed in moderation, especially for those trying to lose weight or manage type 2 diabetes.
• 🔑 The key to managing weight and type 2 diabetes includes reducing intake of sugary foods and being mindful of the fructose content in even seemingly healthy options.

Q & A

Why is sugar considered more deadly than other carbohydrates in terms of weight gain and type 2 diabetes?

Sugar, specifically sucrose, is a combination of glucose and fructose. While glucose can be metabolized by every cell in the body, fructose is primarily processed by the liver and can lead to increased fat production, insulin resistance, and consequently, a higher risk of weight gain and type 2 diabetes.

What are the different types of sugars mentioned in the script?

The script mentions glucose, fructose, lactose, and sucrose (table sugar) as different types of sugars. Glucose is a component of many carbohydrates, lactose is milk sugar, and sucrose is a combination of glucose and fructose.

Why were low-carbohydrate diets considered effective for treating type 2 diabetes?

Low-carbohydrate diets can be effective in treating type 2 diabetes because they focus on consuming fats and proteins instead of glucose. This helps to prevent the rapid increase in blood glucose levels that can occur with the consumption of high amounts of refined carbohydrates.

What was the historical perspective on fructose according to the script?

Historically, fructose was thought to be healthy. For example, in 1986, the FDA stated there was no conclusive evidence that sugar demonstrated a hazard, and as recently as 2006, the American Diabetes Association suggested that sucrose could be substituted for any other carbohydrate in a meal plan.

What evidence started to change the perception of fructose as being healthy?

Studies in the mid-2000s, such as the Nurses' Health Study conducted by the Harvard Medical Center, provided conclusive evidence that fructose is likely much worse than regular glucose, especially in terms of its contribution to weight gain and the risk of type 2 diabetes.

How does the consumption of sugar-sweetened beverages correlate with weight gain and type 2 diabetes risk?

The Nurses' Health Study found a clear correlation between the consumption of sugar-sweetened beverages and both weight gain and the risk of type 2 diabetes. The more frequently these beverages were consumed, the higher the risk and weight gain.

Why is fructose considered worse than glucose for health?

Fructose is considered worse than glucose because it is metabolized almost exclusively by the liver, which can lead to the conversion of fructose into fat, particularly in the liver, contributing to fatty liver disease, insulin resistance, and an increased risk of metabolic syndrome and type 2 diabetes.

What is the process that occurs when fructose is metabolized in the liver?

When fructose is metabolized in the liver, it can be converted into triglycerides through a process called lipogenesis, which is the creation of new fat. This can lead to fatty liver and central adiposity, contributing to metabolic syndrome.

How does fructose consumption affect insulin resistance?

High fructose consumption can lead to increased insulin resistance, as shown by studies where insulin tolerance tests comparing glucose to fructose showed a significant worsening of insulin resistance with fructose.

What advice does the script give for managing weight and type 2 diabetes?

The script advises cutting down on sugary foods and added sugars, and even being cautious with fruits that can be high in fructose, as part of a strategy to manage weight and type 2 diabetes.

What is the role of the liver in metabolizing fructose?

The liver is the primary organ responsible for metabolizing fructose. Unlike glucose, which can be used by every cell in the body, fructose is processed almost exclusively by the liver, where it can be converted into fat if not needed for energy.

Outlines

00:00

🍬 The Destructive Impact of Sugar on Weight and Health

This paragraph delves into the detrimental effects of sugar, particularly in the context of weight gain and type 2 diabetes. It explains the scientific perspective on various sugars, including glucose, fructose, and lactose, and their roles in carbohydrate metabolism. The focus is on the glycemic impact of refined carbohydrates like bread and pasta, which are primarily glucose chains, and how their consumption can significantly raise blood glucose levels. The narrative shifts to the discussion of sucrose, or table sugar, which is a combination of glucose and fructose, and historically considered less harmful due to fructose's natural presence in fruits and its non-glycemic nature. However, recent studies, such as the Nurses' Health Study, have linked high fructose corn syrup and sugar-sweetened beverages to increased weight gain and a higher risk of type 2 diabetes, challenging the previously held belief in fructose's safety.

05:02

🍏 The Metabolic Consequences of Fructose Intake

The second paragraph examines why fructose is more harmful than glucose, despite both being sugars with similar caloric content. The key difference lies in their metabolism; glucose can be utilized by every cell in the body, whereas fructose is exclusively metabolized by the liver. This unique pathway leads to fructose being converted into fat, particularly contributing to fatty liver, central adiposity, and metabolic syndrome. The paragraph highlights studies that demonstrate fructose's role in increasing insulin resistance, a precursor to type 2 diabetes, and how it exacerbates the condition by causing the liver to produce more glucose than needed, leading to lipogenesis. The conclusion emphasizes the importance of reducing sugary foods and even high-fructose fruits in one's diet to manage weight and type 2 diabetes effectively.

Keywords

💡Sugar

Sugar refers to sweet, short-chain, soluble carbohydrates, many of which are used in food and beverages. In the video, sugar is portrayed as particularly harmful due to its impact on weight gain and type 2 diabetes. The script discusses how sugar, especially in the form of high-fructose corn syrup, is linked to increased health risks compared to other carbohydrates.

💡Weight Gain

Weight gain is the increase in body weight resulting from the accumulation of excess fat. The video script highlights that sugar, particularly when consumed in the form of sugar-sweetened beverages, is associated with significant weight gain, as demonstrated by the Nurses' Health Study.

💡Type 2 Diabetes

Type 2 diabetes is a chronic condition that affects the way the body processes blood sugar (glucose). The video emphasizes the connection between sugar consumption and the increased risk of developing type 2 diabetes, as well as the associated risks of other diseases like heart disease and stroke.

💡Carbohydrates

Carbohydrates are a group of nutrients that include sugars, starch, and fiber. The script explains that carbohydrates are generally long chains of glucose, like those found in rice, potatoes, and bread, which can raise blood glucose levels and are part of the reason why low-carbohydrate diets can be effective in managing type 2 diabetes.

💡Glucose

Glucose is a simple sugar and a primary source of energy for the body's cells. The video script describes how glucose is the primary component of blood sugar and how its consumption can raise blood glucose levels, which is a concern for those managing diabetes.

💡Fructose

Fructose is a type of sugar found naturally in fruits and is also a component of sucrose (table sugar). The video discusses how fructose is metabolized differently from glucose, primarily by the liver, and its excessive consumption can lead to negative health effects such as insulin resistance and fatty liver.

💡Sucrose

Sucrose, commonly known as table sugar, is a compound sugar consisting of one molecule of glucose and one molecule of fructose. The script points out that sucrose has been historically considered less harmful than it actually is, due to the misconception that fructose is healthy.

💡Glycemic Index

The glycemic index (GI) is a measure of how quickly a carbohydrate food raises blood glucose levels. The video explains that fructose does not raise the glycemic index because it does not increase blood glucose levels, which was once believed to be a positive quality but is now understood to be problematic due to its other metabolic effects.

💡Lipogenesis

Lipogenesis is the process by which the body creates new fat from excess carbohydrates or proteins. The script describes how fructose, when consumed in excess and unable to be metabolized by the body, is converted into fat through lipogenesis, contributing to weight gain and fatty liver.

💡Insulin Resistance

Insulin resistance is a condition in which the body's cells do not respond properly to the hormone insulin, leading to high blood sugar levels. The video script illustrates that the consumption of fructose can exacerbate insulin resistance, which is a precursor to type 2 diabetes.

💡Metabolic Syndrome

Metabolic syndrome is a cluster of conditions that increase the risk of heart disease, stroke, and type 2 diabetes. The video script connects the consumption of fructose to the development of metabolic syndrome through the promotion of insulin resistance and weight gain.

Highlights

Sugar is considered more deadly in terms of weight gain and type 2 diabetes than other carbohydrates.

Different types of sugars include glucose, fructose, and lactose, with glucose being a primary component in many foods.

Highly refined carbohydrates like bread raise blood glucose levels due to their glucose content.

Low carbohydrate diets can be effective for type 2 diabetes treatment by reducing glucose intake.

Sucrose, or table sugar, is a combination of glucose and fructose with distinct structures and effects.

Fructose was once considered healthy due to its natural presence in fruit and its sweetness.

Recent studies have shown that fructose is worse than glucose, contradicting past beliefs.

High fructose corn syrup has been linked to health issues, including weight gain and type 2 diabetes.

The Nurses' Health Study provided evidence of a correlation between sugar-sweetened beverages and weight gain.

Increased consumption of sugar-sweetened beverages is associated with a higher risk of type 2 diabetes.

Fructose metabolism differs from glucose, being processed primarily by the liver and leading to fat production.

Fructose intake can result in fatty liver, central adiposity, and metabolic syndrome.

Studies have shown that fructose causes more insulin resistance compared to glucose.

Fructose metabolism can lead to a diagnosis of insulin resistance in healthy individuals.

Cutting down on sugary foods and added sugars is key for weight loss and managing type 2 diabetes.

Even fruits, which can be high in fructose, may not be ideal for weight loss or diabetes management.

Transcripts

today we're going to talk about why

sugar is so deadly in terms of weight

gain and type 2 diabetes and much worse

than potentially any other carbohydrate

that's out there and it's coming right

up

when we talk about sugar from a

scientific standpoint there's lots of

different sugars other than what we

think about in terms of table sugar

those are the things that generally end

in oaths like glucose fructose and

things like milk sugar which is lactose

when we talk about carbohydrates they

are generally long chains of glucose so

when you're talking about rice potatoes

flour like bread or pasta for example

those are mostly glucose when we talk

about blood sugar we talk about blood

glucose and that's one of the reasons

why eating highly refined carbohydrates

like

bread can raise your blood glucose very

high because you're eating

long chains of glucose the minute they

get broken down the glucose level in the

blood goes up so that's why low

carbohydrate diets can be very effective

in the treatment of type 2 diabetes

because you're eating fats and proteins

as opposed to glucose

however there's another sugar which we

think about is

sucrose which is table sugar we use it

in baking we use it in many types of

things and that's not glucose it's

actually a combination of one molecule

of glucose and one molecule of fructose

they are slightly different in terms of

their structure but they are both

classified as sugars as are things like

lactose

fructose is naturally found also in

fruit and in fact is one of the sweetest

sugars that can be around

for many many years people thought

fructose was actually healthy for you

in 1986 for example the uh

fda said that there was no conclusive

evidence that sugar demonstrates a

hazard even as recently as 2006 the

american diabetes association said you

can substitute sucrose for any other

carbohydrate in the meal plan so that

was meaning that fructose wasn't

particularly bad for you because

remember sucrose is one glucose one

fructose that glucose is the same as any

other glucose but the fructose is very

different

the question is why it's so bad for you

it doesn't

raise the glycemic index because the

blood glucose doesn't go up when you eat

fructose because that's a completely

different type of sugar

and the other thing is that it's very

sweet and it's found naturally in fruit

so for many years people thought it was

quite

healthy for you to substitute fructose

for glucose

recently though it's become very clear

that this has been a very bad swap

there's been a lot of talk about high

fructose corn syrup and how that is very

bad for you

in the mid 2000s

studies such as the nurses health study

in 2004 started to demonstrate

conclusive evidence that fructose is

probably much worse than regular glucose

this nurse's health study was run by the

harvard

medical center and it followed many

thousands of nurses

documented their habits and compared

them to what happened

when they looked at sugar sweetened

beverages for example from 1991 to 1999

they looked at the correlation between

weight gain and whether people drank

sugar sweetened beverages regularly you

can see that both those that did drink

it and didn't drink it gained on average

about 2 kilos

over that period of time

and it was true whether they drank a

little bit of soda or a lot of soda

however what's more interesting is that

when you switch

from drinking less than one per week to

more than one per day

the weight gain almost doubled

when you did the opposite when you went

from consistently drinking more than one

a day to less than one a week the weight

gain practically vanished so there was

clearly a correlation which was more

than just calories between sugar

sweetened beverages and weight gain and

the true this was also true for type 2

diabetes so if you look at the number of

sugar sweetened beverages the nurses

drank per month

as you drank more and more of these

sugar sweetened beverages the risk of

type 2 diabetes simply goes up and up

and up

and this is

especially bad because of course the two

go together but the type 2 diabetes puts

you at very high risk of other diseases

like heart diseases and strokes

the question is why is the fructose so

especially bad for you much more than

the glucose both are molecules of sugar

both are sweet both have roughly the

same number of calories

the difference is the way that the

fructose is metabolized and glucose can

be used by every cell in the body

so if you're eating

50 grams of carbohydrates say a slice of

bread or something like that

all of your cells in your body your

heart your liver your brain

all

of it can use glucose so if you weigh

180 pounds all 180 pounds of your body

can metabolize that glucose this is not

true however for fructose

when you eat the same amount of fructose

none of your body except for the liver

can actually metabolize that fructose so

your your heart your liver your kidneys

they can't use that fructose in fact the

only place that it can go is straight

into the liver

and when it goes into the liver what

happens is that it turns into fat

looking at this diagram

what you see is that the fructose

is absorbed through the intestines goes

straight into the liver so instead of

all 180 pounds of body using up the

glucose you have maybe five pounds of

the liver metabolizing that fructose and

it can get turned into glucose however

if you're eating a lot of carbohydrates

or if you're eating sucrose which

already has glucose your body doesn't

need more of that glucose so that's one

way that it can be metabolized that's

blocked off the only other way it can go

is get turned into triglycerides which

is a process called lipogenesis or the

creation of new fat

what you get is fatty liver and then the

body tries to deliver tries to export

that fat out through vldl so you get

central adiposity and the metabolic

syndrome so in fact the fructose is much

much worse for you because there's

simply no way to get rid of it all as

opposed to using the the rest of the

body to metabolize it

several studies had shown very early on

that when you compare glucose to

fructose you get much more of this

insulin resistance because of that fatty

liver

we talked about fatty liver in the past

and how it's very closely related to

insulin resistance which then causes

type 2 diabetes it turns out that if you

do a insulin tolerance test

comparing a dose of glucose to a dose of

fructose you get about 25 worsening of

insulin resistance

in 2009

in the

jci they published a very interesting

study where again they looked at giving

people glucose versus giving them

fructose and even these normal healthy

volunteers when they get the fructose

their blood glucose levels goes up to a

point that you can actually diagnose

insulin resistance

so the high insulin resistance then

causes high insulin levels in order to

try to metabolize it you get the fatty

liver and there that starts you on the

pathway towards

metabolic syndrome type 2 diabetes and

weight gain so when you're looking at

the fructose versus the glucose you have

to recognize that the fructose the way

that it's metabolized is makes it much

much more likely to get turned into fat

to get turned into the bad type of fat

which is the liver fat

and that causes the insulin resistance

which gives you this very high rate of

type 2 diabetes so really

the key if you're starting to lose

weight is really to cut down those

sugary foods especially the added sugars

even the fruits which can be very high

in fructose sometimes are not your best

friend if you're trying to lose weight

or manage type 2 diabetes thanks very

much for watching

see you next week