Sugar and Obesity – Fructose 3

//Sugar and Obesity – Fructose 3

One of the most intuitive facts in nutrition is that eating lots of sugar makes you fat. I don’t really think that there is all that much disagreement on this point. There is certainly some argument about why this is true. The calories people claim that this is because it is a source of empty calories. So, therefore, you could eat sugar and skip dinner and not gain weight. These people believe that eating a plate of brownies with some multivitamins and an equal calorie portion of kale salad with salmon is equally fattening.That’s idiotic not likely to be true, as common sense would tell you. The calories people claim that since sugar is empty calories, you will then eat more food with nutrition, as if it’s really, really hard to avoid eating nutrient dense foods like liver, calf brains and kale. Hold me back…Can’t resist…The stewed calf brain….

I argue that the fructose is far worse than glucose because it causes fatty liver directly and therefore insulin resistance. This feeds into the vicious cycle of hyperinsulinemia and insulin resistance. I believe that it is the insulin resistance cycle that sets the ‘Body Set Weight’ and to successfully lose weight in the long term, you must address this cycle.

Both glucose (starches) and fructose play a role, but enter the cycle at a different point. If you eat massive amounts of carbohydrates in the form of glucose, it is still possible that you do not develop this vicious cycle if you do not have any fructose. As an example, the Chinese diet of the 1990s was extremely high in white rice (a refined carbohydrate and with lots and lots of glucose) but almost no fructose. They were also not eating 32 meals spaced throughout the day, so they weren’t keep insulin levels high.

Under this circumstance, there was very little obesity and even less type 2 diabetes. As the diet began to Westernize, and sugar consumption increases, this is simply a recipe for disaster and China has now passed the US in diabetes prevalence.

Since sucrose (table sugar) contains both glucose and fructose, it is especially dangerous. Fructose can only be metabolized by the liver, so 1 pound of sugar has 1/2 pound of both glucose and fructose. The entire body uses the glucose, but only the 5 pounds of liver needs to metabolize the same amount of fructose. Furthermore, the fructose will not be metabolized to glucose in the liver, because the body has just taken in a bunch of glucose. The body does not need any more glucose. Instead, the body will get busy turning that fructose into fat through de novo lipogenesis. Hey presto – fatty liver. Hey presto – insulin resistance. Hey presto – increased body set weight. Hello, diabesity.

So, I believe that fructose is something like 20 times more fattening than glucose (starches), as we discussed last week. So it is not really true when somebody says that eating a bowl of rice is the same as eating a bowl of sugar. A bowl of sugar is more like eating 20 bowls of rice. That is why fructose, specifically, is so, so fattening. That is really why reducing sugar is the most important step in reducing obesity. That is why those true calorie believers are so dangerously ignorant when they say that sugar is no worse than any other calorie. This, of course is the point behind Gary Taube’s excellent new book ‘The Case against Sugar‘.

So what are the top sources of fructose in the diet? Beverages is the top source of sugar and should obviously be reduced. But the issue is whole fruit. It makes up a sizeable 18% of dietary intake. Should we reduce it? I confess that I do not have a good answer here. Biochemically, there is no difference between fructose in fruit and fructose in sugar.

However, there are an number of mitigating factors in whole fruit, including fibre. Is it enough? There is no good answer. Epidemiologic evidence does NOT link whole fruit consumption to obesity or diabetes, but that is not quite enough for me to give it a free pass.

Without adequate data, the best answer I can give is this. If whole fruit is the worst that you do in your diet, that’s OK. However, if you need to reduce weight, then consider reducing fruit. Yeah, I know, not a very good answer.

In response to Gary Taube’s book, there have been some who have responded that dietary consumption of sugar peaked and yet obesity continues to go up. This is considered ‘proof’ by some that sugar does not play a large role in the cause of obesity.

At first glance, this may appear to be true, and is certainly persuasive. However, a closer look reveals the truth.

Let’s look at an analogous case of why smoking doesn’t cause cancer. The relationship between cigarettes and lung cancer. Here’ the graph of cigarette smoking and lung cancer. Well this first graph shows that smoking ‘obviously’ was not a major cause of lung cancer, right? As the number of cigarettes goes down, lung cancer deaths continue to rise. All those anti-smoking people should be ashamed of themselves for all that fear mongering. Jeez.

Well, let’s fast forward a few years. Here’s the full graph. There’s simply a time lag between smoking and lung cancer. That’s life. What you can see, when you look closer at the first graph is that the rate of rise of lung cancer death starts to slow as cigarette consumption drops. That’s the first step.

The same is true in sugar. Obesity is a multifactorial disease. Certainly sugar is one of the biggest factors, but not the only one. Reducing sugar doesn’t mean that consumption will go down right away, and the effects may need years or decades to show a difference. That does NOT mean that the hypothesis that sugar is a causal factor is incorrect. Let’s look a bit closer at the data. I’ve put up the graph of obesity from the OECD and the USA data is highlighted in red.
You can see that after the year 2000 there are two lines. The bolded line shows the actual incidence of obesity. The dotted line shows the past projection of obesity. In other words, the data clearly show that the rate or rise of obesity has clearly slowed.

Obesity was rising at a fast rate from 1977 to 2000. There is a momentous inflection point right at the year 2000. Obesity slows. Why? What happened? The Y2K bug? No. Sugar consumption peaked and then fell. The growth of obesity slows down.

2017-10-12T22:21:05+00:00 49 Comments

About the Author:

Dr. Fung is a Toronto based kidney specialist, having graduated from the University of Toronto and finishing his medical specialty at the University of California, Los Angeles in 2001. He is the author of the bestsellers ‘The Obesity Code’ and ‘The Complete Guide to Fasting’. He has pioneered the use of therapeutic fasting for weight loss and type 2 diabetes reversal in his IDM clinic.

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49 Comments on "Sugar and Obesity – Fructose 3"

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Dr Yogesh Kulkarni
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The fruits our ancestors ate is not what we eat today. We are eating modified agricultural product called fruit. Sugar contents of fruits were very low before the modification as compare to today. We human vitiated the nature by modifying the genes of plants under the name of modern science and development.
Dr.Jason hesitation in saying stop fruits because it’s very difficult to convince people. Today we are not eating fruits but fruit like substance. Too much of fructose in fruits rob away the goodness of nutrients.

Mr Tarzan
Guest
Thank you Doctor, What puzzles me is the conundrum over fruit. Humans descended from primates, and our closest relatives are chimps and bonobos. These two species eat a lot of fruit – especially figs – amongst other things like limited meat and a wide diversity of plants. (https://blogs.scientificamerican.com/guest-blog/how-to-eat-like-a-chimpanzee/) In the history of human evolution, presumably we ate a lot of fruit. Examinations of tooth enamel in early hominoids show that our pre-human ancestors had a diet of primarily fruit. (Rensberger, Boyce (May 15, 1979). “Teeth Show Fruit Was The Staple; No Exceptions Found”. The New York Times) I would assume… Read more »
Greg Mu
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“Obesity is a multifactorial disease.” That must be kept in mind–as well as the notion that things were DRASTICALLY different 20,000 years ago and beyond–when approaching the notion of what causes obesity in modern times. To name a few things that MAY have been different 20,000 years ago: -fruit was only eaten in season (bananas the size of your arm weren’t perfectly ripe on the shelf every day of the year); -fruit wasn’t on steroids (the average size of a peach was slightly larger than a marble, bananas were likely the size of your small finger) and therefore the sugar… Read more »
BobM
Guest

Greg, supposedly it’s a myth that our ancestors moved more than our modern selves, at least if we’re talking about aboriginal type cultures. They try not to move much, although of course they have to do some movement to get food. But once that’s done, they don’t move much until the next time it’s time to get food. Is this true? I have no idea, but I personally don’t place much emphasis on “exercise” or “work” as a reason for obesity.

Stephen Town
Guest
Greg, I read recently that ancient apples were so bitter that modern man would struggle to eat them. And as you say, fruit was available only in the summer and each fruit for probably quite a short period. We’d have eaten anything we could get out hands on, but given the choice, I think meat and fish, if available, would have been preferred. If we eat a sugar and junk free diet, I think fruit is a marginal issue. I eat berries with my full fat yoghurt, but avoid very high sugar fruits. Avoiding Junk, soda and processed foods is… Read more »
Susan Weiss
Guest

Also, my Doc pointed out to me that fruit is generally in season…late summer/early fall, a time when we would WANT to fatten up to get through a lean winter.

johnnyv
Guest

Our closest LIVING relatives are chimps, there are many extinct hominid lines which are of course far closer to our physiology as we evolved from them.

Our digestive tract is very different to a chimps, we do not have a massive colon like a chimp so no significant fiber fermentation potential. We do have a very large small intestine like other more carnivorous omnivores.

glib
Guest

Yes, but since this post is about fructose, the real question is: are a human and a chimp liver really different?

Brian
Guest
Something to keep in mind, think of when fruit is primarily in season.. summer. After summer it starts to cool down, then winter hits. Could the natural seasonal nature of fruit specifically be to fatten someone or something up before winter? Animals for instance, will go haywire on the fruit during the season.. bears for example before hibernation. Fruit by nature is not something available 24/7 365 days of the year. It’s not as big as it now in some cases. Humans also had competition from other living things when fruit became available. So for someone to have their 1… Read more »
Kamila
Guest
The theory that human ancestors were fruit eaters, is not really convincing – our teeth suggest the opposite, if our ancestors ate fruit, we would be able to eat them without having rotten teeth and falling apart gums. As it is, the only food that does not destroy our mouths is meat and fat. Carbohydrates, and sugars in particular, are not good for dental health. And if our ancestors indeed ate fruit and carbs in huge doses, they would quickly lose their teeth and die. For more info check: http://donmatesz.blogspot.fr/2017/05/graecopithecus-casts-doubt-on-out-of.html It’s a compelling article I found just recently. It shows… Read more »
Boelie Hoekstra
Guest

Robert Lustig said about fruit that we only eat it in the season, one month a year, two months at the max.
We get now overdosed i guess with fruit and sugar the whole year.

glib
Guest

But if you were near the equator, a long time ago, every day would be in season. There are numerous non-seasonal fruits (coconut is the best known, but also lemons).

Soňa
Guest

As for coconuts, they are more fatty than sweet so for them I don´t see any trouble. Even near equator and anywhere where conditions are convenient for fruit growing, you still have seasons or call it cycles. It still needs to grow, ripen, rest a while to grow and ripen again. It can be available for more than a month or two but still it´s not non-stop (if you leave to nature only, not agriculture by human).

glib
Guest

you are right, I should have mentioned banana, guava, papaya and pineapple right from the start. Those are sugary and non-seasonal. Jackfruit is basically non-seasonal. Either way, I lived in Brazil for 8 months and returned numerous times, these foods are and were available year round.

The Intelligent Omnivore
Guest
The Intelligent Omnivore

But we are not near the equator, end of story.

Mr Tarzan
Guest
Caveats to the above: Please note that I am talking about eating whole fruit – not juicing it – so that the fibre is digested. I am also talking about a daily amount of 1 banana, 1 apple, 1 guava, 1 grapefruit and some cherries on a non fast day with the rest of the ‘low card/Paleo type’ diet mainly greens and a small amount of grassfeed beef etc. Not an entire watermelon for example. And I realize that fruit is bred sweeter now than ‘ancient’ fruit. (https://www.newscientist.com/article/mg22730322-100-bitter-truth-how-were-making-fruit-and-veg-less-healthy/) And I realize that chimps and our ancestors moved more than us,… Read more »
Ellen
Guest

I ate apples from an pre-revolutionary war orchard. Not having any care for a century or two, meant the fruit was small and a bit wormy. However it was a sweet as apples you can buy today. Not tart like a Granny Smith, more along the line of a Mac or a golden.

BobM
Guest

Interesting. I ate apples from an apple tree in my grandparent’s yard, and they were small and very tart. The same for pears at another location near my grandparent’s. I ate them, but they were only available not much of the year (though supposedly one could put them in a barrel filled with water, which would make them last a while).

glib
Guest

It is well known that bears in Kazakhstan selected sweet apples over millions of years. In a good year, they would only eat sweet apples and propagate their seed. As a result there is a discrepancy between the fraction of sweet apples in Tian Shan (about 1%), and what is calculated from genomics (about 0.01%). Bitter apples were and are still grown, for hard cider. Hard cider from sweet apples is undrinkable.

Josh
Guest

Take a look here:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0132672
“Soybean Oil Is More Obesogenic and Diabetogenic than Coconut Oil and
Fructose in Mouse”

Suggests there may be more than one factor at play as well. Still linked to processed foods and shows fructose has similar effects (doesn’t look like they try sucrose which might be more nefarious for DNL?) but puts linoleic acid at the top of the list for obesity and insulin resistance. Would love to hear your take on this. Peter over at Hyperlipid has been looking at linoleic acid a lot lately.

George
Guest

@Mr Tarzan,
Researcher Barbary Corkey hypothesizes (and has some data) that food additives may be a cause of hypersecretion of insulin. Our primate monkeys weren’t eating processed food. Perhaps without a lifetime of food additives in processed food the system could handle whole fruit.

See: “Are Insulin Hypersecretion and Food Additives a Cause of Obesity and Diabetes? IAS Distinguished Lecture
Date: 15 Apr 2016 https://www.youtube.com/watch?v=R453JTyBCK4

Cynthia S
Guest
After a series of ~60 hour fasts roughly once a week, my morning ketones are progressively getting higher: 2.4, 3.1, 3.4, 4.2. Is this just an indication of increasing efficiency in burning fat, or can this be an indication of reducing insulin resistance? I combed this site and elsewhere for an answer and can’t find any indication of what is going on. Anyone have an idea? Background, currently ketogenic. lost 50 pounds so far on low carb, but have been moving over the last 2.5 years to a more efficient form of low carb diet: less carbs, less protein, more… Read more »
glib
Guest
I have something to offer about fruit consumption. For years I was a sort of higher carb paleo. In late 2013 I checked my blood to find a blood glucose of 103 but also a TG/HDL of 5, which is worrisome. Back then I was eating large amounts of rice but mostly 4-6 apples a day in winter, no sugar, no other grains. I ate other fruits too, so let us say 8 fruits a day, with apples the majority during the Oct.-May period. My intake of greens has remained steady, and fairly high, perhaps an uptick during the growing… Read more »
The Intelligent Omnivore
Guest
The Intelligent Omnivore

You changed way too many variables at once to ever use your N=1 as evidence for anything.
But for me, I need to lose fat and based on what I have done in the past, including an all fruit diet, I avoid fruit 99% of the time.
Fructose has to go somewhere and it’s got to go through the liver.

glib
Guest

not really, it was more greens and more fat, and less of everything else, but in particular it was 3-5 fewer apples a day.

J L De Foa MD
Guest
I suspect one reason the jury is out on whole fruit sourced glucose + fructose + sucrose (most fruits are about 50:50 glucose:fructose but have varying proportions of those as actual sucrose) is that many of the folks who bother to eat more unprocessed / whole fruit (and green veggies too) are the same folks who DON’T consume HFCS sweetened drinks, potato chips, etc.. So is it more “the good” or less os “the bad” which makes the difference? In a word, “confounding”. Also, those stories about ancient fruits may be contrived. Denise Minger has a good review about it.… Read more »
Roger Bird
Guest

But many of our very fine commentators here are going back to evolutionary time to find the solution, not the culprit.

Peter Azlac
Guest
Whilst your comment about sugar consumption in the US peaking in 2000 may be correct – looking at the data it is not clear whether sugar from fruits and milk is included – the total simple carbohydrates (sugar plus grains) did not, such that total intake of glucose and fructose was little different but fructose probably made up a higher proportion as it is now endemic in most processed foods and drinks. https://www.ars.usda.gov/ARSUserFiles/80400530/pdf/1314/Table_1_NIN_GEN_13.pdf https://www.usda.gov/documents/usda-factbook-2001-2002.pdf Other considerations are the consumption and effect of trans fats and the fact that in 2000 the average consumption of calories was 24% above needs, and… Read more »
Engr_Rene
Guest

There’s a new movie out, I have yet to see, it’s called “A Cure for Wellness”. You know what it is?

ADA Nutrition Guidelines

Have a good weekend everyone!

The Intelligent Omnivore
Guest
The Intelligent Omnivore

Why is it such a crime to say “do not eat fruit”?

1. Obviously fruit per ounce is much less damaging than sugar per ounce.
2. If you have obesity issues, why would you knowingly take in extra fructose? Don’t eat fruit (right now).
3. If you are thin and have perfect blood tests, eat some fruit, if you want.
4. End of story.

Sue
Guest

…..laughing…. exactly. My husband is (was!) T2D and we both still have weight to lose. We eat almost no fruit. (Right now.) We might sometimes have some berries but that is considered a treat. Fruit is nature’s dessert. And we probably shouldn’t eat dessert every day. 🙂

Loved your comment.

Roger Bird
Guest

Hey, TIO, you are very sure of yourself with that “End of story” line. (:->) But I do happen to agree with you.

A good test would be to go without fruit for a while to see what happens. And then eat a lot of fruit to see if it makes you hungry. Regular sugary crapola makes me hungry and is a threat to my fasting. Tomorrow I will try eating a bunch of sweet fruit and see if it makes me hungry.

Peter Azlac
Guest

I should have quoted some of the research on the impact of trans fats on the metabolism of glucose and triglycerides in the liver. The current view is that it involves the effect on, “peroxisome proliferator-activated receptors (PPAR) and liver X receptors (LXR) as lipid-sensors that regulate lipid and glucose metabolism as well as inflammation”

https://www.researchgate.net/publication/228481678_Trans_fatty_acids_insulin_sensitivity_and_type_2_diabetes
http://www.sciencedirect.com/science/article/pii/S1567568806000341
http://jn.nutrition.org/content/136/3/690.full

Roger Bird
Guest

I hope the food industry doesn’t try too hard to find a “healthy” artificial trans-fat, because no matter how healthy they say it is, if it is artificial and/or non-paleo, I’m not eating it.

kelly
Guest

I am so confused about fructose now……. do this mean i shouldn’t eat fruit any longer because fructose in a diet is unhealthy? i eat fresh fruit almost daily, about 1 or 2 servings a day with home made full fat greek yogurt.

Sue
Guest

Kelly, if you are insulin resistant, diabetic or need to lose weight, don’t eat fruit. You are just adding unnecessary sugar to your diet. If you have no health concerns that are made worse from added sugar then have some fruit.

glib
Guest
agree. let me add that those who reduce fruit reduce their vitamin C. They reduce also some minerals but it is easy to get those back with a little bump in vegetables in general and greens in particular. But vitamin C and acidity (useful to start and improve digestion) typically comes from fruits, as well as enzymes if you eat your vegetables cooked. This is where fermented foods come in. They are acid, enzyme rich, and they have some vit. C, but more than that they have a whole spectrum of anti-oxidants that can play one of the most important… Read more »
Roger Bird
Guest

Nice response.

Thomas
Guest
Kelly, the real culprit is INSULIN, which leads to insulin RESISTANCE! Fructose in its natural form with fiber is NOT the culprit as our liver can actually metabolize small amounts (1-2 servings per day) PROVIDED we do not overload the liver with SUGAR (glucose) based nutrition (empty calories). Cruciferious vegetables (Kale, Broccoli, Cauliflower, etc) will clean up the liver from small amounts of fructose in its natural form, and the spike in insulin is not that high with such intake. HOWEVER, if the liver is already taxed by high glucose, then it is best to avoid fructose in its totality.
Stephen Town
Guest

Kelly, Dr Fung doesn’t say to stop eating fruit in the article. Our bodies can cope with some fructose, but I don’t want to overdo it.

If we eat a sugar and junk-food free diet, I think fruit is a marginal issue. I eat berries with my full fat yoghurt, but I avoid fruits that are very high in sugar, such as pineapple or magos. Avoiding sugary Junk, soda and processed foods is surely the priority.

Ali
Guest
Fruit in itself isn’t bad, but it can often lay down fat for the cold winter months. Eating it out of season is the biggest issue. The biggest difference between whole fruit and sugar is that unlike sugar, whole fruit is rich in nutritional elements, phytonutrients, antioxidants and electrolytes, particularly potassium. In our sodium-rich, potassium-poor Western diet few of us get enough potassium to offset the sodium. That imbalance can cause major issues even way before we get to a critical deficiency level. Blood tests reveal little. Because the body will always attempt to keep the blood electrolyte levels balanced,… Read more »
Cornish
Guest

Very interesting article. Could I put in a request for a similar one about how alcohol is metabolised in the liver and how it compare to fructose. Is one worse than the other ?

Sharon deRham
Guest

I would love to see the same thing–how alcohol is metabolized. I love fine wines–I live in the south of France in the Rhone Valley and one reason I moved here is for the wines. However recently I have almost completely stopped drinking because I don’t believe all the hype about how healthy wine is. It must makes me fat! Would love to understand the alcohol/fatty liver/diabetes connection. I “was” pre-diabetic but have been eating kept for about 6 months and am fine. Need to sty that way.

Lilli
Guest

Interesting discussion. According to Professor Oluf Borbye Pedersen at Copenhagen University, Denmark, our microbiata seem to be influenced by the fruit and veggies we eat, and in accordance to the microbiata research he has made during the past two years, the microbiata also strongly influences obesity, this can be of signicant interest to whether or not, we should include fruit on a daily basis in our diet.

Mediterranean ape
Guest
If someone advocates no to eat carbs or sugar and is mentally o.k he should ask himself or research what are the side effects of his action ?for example if you go on 0 carbs 0 sugar are you 100% sure that it will not affect negatively your health ? Is it proven by any clinical trials that can not damage your body?backed by science? As I watched some ‘ Drs” advice O for both ! Carbs and sugar we are here after thousands of years we eat both in small quantities , , ,doctors change their opinions as the… Read more »
Ken Stephens
Guest
Fructose gets a bad rap overall and a lot of this is myth. I don’t think there’s any question that glucose is worse for us actually, and with our current diet we may even have a fructose deficiency, and especially if one has type 2 diabetes. I used to think fructose was a villain until one day I read some articles on this by Ray Peat which did open my mind quite a bit. The part about fructose being so bad for liver fat is actually the result of a very ill conceived experiment, where they gave people some extra… Read more »
S sing
Guest

Has anyone read the medical medium. He states the main problem is the adrenal glad ( cortisol / adrenaline). Thus the adrenaline damaging the pancreas, and the mixture or animal fat also not helping. He actually recommends more fruit in the diet and no dairy. Limited grains and lower meat consumption.

He basically is saying food is half the answer. Adrenaline coursing through your body through constant negative emotion is the big whammy. Not food as everyone is concentrated on.

April
Guest
Dear Dr Fung, can you please tell me something more about the so called polyols cycle. I read about it and I get really confused. It says : if large amounts of glucose are present (as in diabetes mellitus), hexokinase becomes saturated and the excess glucose enters the polyol pathway when aldose reductase reduces it to sorbitol. This reaction oxidizes NADPH to NADP+. Sorbitol dehydrogenase can then oxidize sorbitol to fructose,… Are polyols bad for our liver and body? Can we consume them in small amounts as a sweetener as they do not raise insulin? Or are they as bad… Read more »
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