The Real Cause of Obesity

Robert Lustig

Lustig in the centre

Professor Robert Lustig had two very good lectures at the ASBP obesity conference last weekend. As you can see above, the attending doctors were very interested in talking to him and asking questions afterwards.

The topic for the talks: Why do we get fat, and how can we treat it? Professor Lustig understands the answers better than anybody else I know.

Here are some of the insights he shared in his talks: 

It’s the insulin, stupid


Some people still deny that insulin has anything to do with obesity. These insulin-deniers are mostly academic researchers who don’t actually treat obese patients.

Most of the obesity doctors at this conference, including most speakers, were very well aware of the central role of insulin in obesity. Professor Lustig certainly agrees. He understands it better than almost anyone.

The chicken or the egg?


This is a very interesting question. Obese people have high insulin levels and they have insulin resistance. What comes first?

The conventional view of the flat earth people (the insulin deniers) is this:

Eating too much (gluttony, sloth) makes you fat. The fat makes you insulin resistant and that raises your insulin levels.

The low carb people, who realize that low carb makes a lot of people lose weight effortlessly, see things like this instead:

Too much carbs raises insulin (and then insulin resistance) and makes people fat.

This second view, I think, is basically true. But it’s not necessarily the whole truth. I think professor Lustig has an even better explanation:

There is no chicken


In Lustig’s view there isn’t one specific chicken. The problem can start anywhere:

  • Insulin resistance (perhaps because of too much fructose in your diet) raises the insulin and makes you gain weight.
  • Too much insulin (due to rare brain damage or, more conventionally, excessive carb intake) eventually makes you insulin resistance. It’s basic physiology: high levels of a hormone eventually down-regulates its receptors.
  • Obesity (for whatever other reason) makes you insulin resistant which raises insulin levels.

The problem can start anywhere.

Leptin – the roadblock to obesity

Looking at the slide above it seems like it’s easy to get fat. Why doesn’t it happen to us all? The answer is the hormone leptin.

Leptin is produced by the fat cells. When we fill our fat stores leptin goes up which tells the brain that we don’t need to eat more. This should normally stop us from becoming obese.

The problem is that high levels of insulin blocks the leptin signal in the brain, making obesity possible (see Lustig’s recent AHS talk).

Conclusion: Target insulin

Here is the conclusions slide from Lustig’s talk:


Basically: Lowering elevated insulin is an essential part of obesity treatment.

The most effective way to lower insulin? Diet change.

What kind of diet change? Here is the program from Lustig’s clinic:

How to do it


No sugar and no white non-fiber carbs (white bread, pasta etc.). And EAT REAL FOOD. I could have said it myself.

Lustig doesn’t necessarily recommend an even more strict LCHF diet (very low carb). He considers that somewhat extreme. Instead he says eat slowly and exercise more.

This is all fine. I think the program above is great.

The next step

However, for a lot of people the program above is not enough to normalize the weight or other metabolic problems. For others it’s too slow.

If you want an even more effective dietary program you need to be even more strict with the carbs, lowering insulin even more. Then you need LCHF. If you do that you may not necessarily need to eat slowly or exercise more. It may be effective enough anyway.

Paradigm shift: The Earth is round

The continuing epidemics of diabetes and obesity are two massive ongoing disasters. How do we stop them? Step one is to dump the failed medieval mindset that obesity is just a result of gluttony and sloth.

Obesity is usually the result of a hormonal imbalance, most commonly too much insulin (the body’s main storage hormone).

When we realize this there is often a simple solution.


I interviewed dr Lustig at the conference and the video will soon be posted.

Obesity and the trouble with sugar

Guyenet, Taubes and why low carb works

Low carb winning 14 – 0

Why Americans are obese: Nonfat yogurt

The American obesity epidemic 1989 – 2010


  1. Ok, yes, what we eat matters. No doubt about it. And, yes, I myself have experimented with a LCHF diet and I can say that it leads to weight loss almost as a side-effect.

    Still, it seems impossible to stuff oneself and still expect not to gain weight. In other words, there have to be very few foods that can be eaten in huge amounts regularly and don't lead to obesity eventually. Any 4,000+ calorie diet will make most people fat.

  2. Txomin,
    Possibly. But what kind of diet makes you want to eat 4,000+ calories? My answer would be: probably a Western high sugar/starch junk food diet.
  3. eddie watts
    as someone who deliberately ate a 5000 calorie diet daily for about a year while training for strongman i can say it is not easy and without some external driver (ambition to compete...or hormones say) it is not something many would be able to do longterm.

    certainly i cannot imagine someone doing it without noticing they were over-feeding without some other factor urging them on

  4. FrankG
    Another paper worth reading... this time from some smart folks in the Netherlands:

    September 2011, vol. 69, no 9 The Netherlands Journal of Medicine

    The dietary intake of saturated fatty acids (SAFA) is associated with a modest increase in serum total cholesterol, but not with cardiovascular disease (CVD). Replacing dietary SAFA with carbohydrates (CHO), notably those with a high glycaemic index, is associated with an increase in CVD risk in observational cohorts, while replacing SAFA with polyunsaturated fatty acids (PUFA) is associated with reduced CVD risk. However, replacing a combination of SAFA and trans-fatty acids with n-6 PUFA (notably linoleic acid) in controlled trials showed no indication of benefit and a signal toward increased coronary heart disease risk, suggesting that n-3 PUFA may be responsible for the protective association between total PUFA and CVD. High CHO intakes stimulate hepatic SAFA synthesis and conservation of dietary SAFA. Hepatic de novo lipogenesis from CHO is also stimulated during eucaloric dietary substitution of SAFA by CHO with high glycaemic index in normo-insulinaemic subjects and during hypocaloric high-CHO/low-fat diets in subjects with the metabolic syndrome. the accumulation of SAFA stimulates chronic systemic low-grade inflammation through its mimicking of bacterial lipopolysaccharides and/or the induction of other pro-inflammatory stimuli. The resulting systemic low-grade inflammation promotes insulin resistance, reallocation of energy-rich substrates and atherogenic dyslipidaemia that concertedly give rise to increased CVD risk. We conclude that avoidance of SAFA accumulation by reducing the intake of CHO with high glycaemic index is more effective in the prevention of CVD than reducing SAFA intake per se.


    The total body of evidence suggests that attention should be shifted from the harmful effects of dietary SAFA per se, to the prevention of the accumulation of SAFA in body lipids. This shift would emphasise the importance of reducing dietary CHO, especially CHO with a high glycaemic index, rather than reducing dietary SAFA. The chronic interaction of SAFA with our immune system elicits so-called chronic systemic low-grade inflammation, which underlies the metabolic changes referred to as the (atherogenic) dyslipidaemia of the metabolic syndrome or the lipidaemia of sepsis. The ultimate goal of the ensuing insulin resistance is the re-allocation of energy-rich substrates, such as glucose, to the immune system while the change in our lipoprotein profile aims at the limitation of the inflammatory responses and the repair of the resulting tissue damage. Dietary SAFA belong to the many false triggers of inflammation that result from the conflict between our slowly adapting genome and our rapidly changing lifestyle, but among these many factors they are not the most important. A reduction in the consumption of CHO with a high glycaemic index, trans-fatty acids and linoleic acid, and an increased consumption of fish, vegetables and fruit, and a reduction of inactivity, sleep deprivation and chronic stress seem more realistic approaches to fight the current pandemic of cardiovascular disease resulting from chronic systemic low grade inflammation."

  5. Great interview with Lustig, Andreas!

    Calm, relaxed and very clear!

  6. FrankG
    Ivory Towers..?

    The Helsinki Times - Thursday, 03 November 2011
    "Professor attacked by low-carb fanatics"

    “Low-carb devotees attack nutritionalist Professor Matti Uusitupa like they were involved in a holy war. Uusitupa is one of Finland’s leading nutritional experts, but in spite of this people on the net like to sling huge handfuls of mud at him. On internet discussion boards, his judgement is called into question and some suggest that he’s been getting money for the statements he’s been making.

    One commenter in Aamulehti put it like this:

    ‘How extraordinary! For too long Finns have believed in the words of our masters and those doctors who’ve designated themselves experts! As if low-carb diets are a mere fashion and the people who follow them idiots. No: people have chosen low-carb diets, because they’re actually beneficial to these people!’

    Uusitupa has said that illnesses will start to increase if the boom in low-carb diets and the use of fatty dairy products continues for another 3-5 years. In particular, the professor doesn’t think it’s a good idea to reject products made from whole grains.

    In the tabloid Iltalehti, Uusitupa said that he had received obscene messages from low-carb advocates. He says that low-carb diets stir people’s feelings, because it’s more a question of belief than anything else.

    Uusitupa has worked in numerous domestic and international expert commissions in the areas of diabetes, cardiovascular disease and nutrition.”

  7. Galina L.
    One of main problems with the obesity treatments - there is too much guessing. I think I was insulin resistant more 4 years ago than now, after 4 years of the LC eating. It would be perfect to know how my lepton changed and how high is my insulin level now. I think it is important to start testing people , especially the obese ones, for the insulin sensitivity and the basal level and lthe eptin deficiency. Nobody knows much about the whole medical picture in each particular case and just assumes that the obese or overweight person spends too much time on the couch with a gallon portion of an ice-cream. It is quite possible for other people to guess that I lost weight just because I started to eat less on a high-fat food, or my health improved only because I was allergic to wheat and don't eat eat it any more together with other grains.
    The changes I suggested are impossible until the main treatment for excessive weight would be the calories counting diet.
  8. JAUS
    #1 I ate 4000+ calories when I lost my weight at my fastest rate. Only way to gain weight with fat is if you have another hormone imbalance, cortisol as an example, but the fat is still not the cause for the weight gain. Regardless how much fat you eat you won't gain weight as long as you have normal hormone levels.
  9. JAUS
    #8 I forgot to add that I did not exercise at all during that time, in fact I spent almost all my time in bed. It was only the LCHF diet that made me loose the first 15 kg (33 pounds). The first 10kg took only a month to loose.
  10. moreporkplease
    Gary Taubes has quoted studies showing people won't normally overeat, Txomin. So for most people counting calories probably isn't necessary. I urge you to try to overeat - it makes you feel uncomfortable and the vast majority of folks will naturally stop. I urge you to try the butter experiment. Sit down with a spoon and a half kilo of butter. See how much you can stand to eat naturally, without unduly forcing yourself. I've tried this myself and couldn't do more than 3 spoonfuls. I met one person who did 5, but he forced that last one down and then couldn't stand the sight of butter for a couple of days. :)
  11. I second JAUS on his statement. I also had my greatest weightlost while eating 4000+ calories. It was in the first period after changing my diet from western to HFLC and i dropped about 20 kg in 4 months.
    Today , 2 years later im stable at a perfect weight and my food intake is at an all time low, I need only 1-2 normal meals a day.
  12. The cause of Obesity Link to the video for those, like me, who are impatient. Really enjoyed it. Very easy to understand. I hope it gets lots of views. Please share the link in as many places as possible.
  13. FrankG
    Thanks for posting that link Ted.

    Bravo Doctor Andreas! Excellent interview with Professor Lustig... I have already shared it on three Diabetes forums.

    It was very well paced, and just long enough for detail; while not too long for those who can't seem to find the time to learn new things ;-)

  14. Mike Ellwood
    Great interview, and great summary. Dr Lustig's presentation at AHS was also very good.
  15. Tom
    Can't wait to watch the rest of that video, Andreas.

    But what a treat it will be -- from what I skimmed so far, a wonderful conversation between two people who really 'get it.'

    Nicely shot & edited, too.

  16. Jaime
    Thanks for the video! Very interesting (as everything from Lustig) and great quality!
  17. eddie watts
    cannot wait to get home and watch that video!!!
  18. Really interesting video, thank to ted for the video link
  19. Barbara
    The real cause of obesity is by eating high cholesterol foods like egg, meat and etc. This is the reason why many people suffer from obesity. To avoid this kind of disease, must maintain your meal, exercise regularly and most especially consult to the doctor.
  20. @ Barbara
    If it were the case "The real cause of obesity is by eating high cholesterol foods" then we would expect STATIN use would produce weight loss as a side effect. Given the 'dangers' of cholesterol need to be reviewed as it's now recognised for women, moderately elevated cholesterol (by current standards) may prove to be not only harmless but even beneficial. Statin makers are desperately seeking new potential markets to preserve their income stream. They would not be overlooking this side effect if it were the case that statin use (reducing cholesterol) caused weight loss. There is no evidence to support such a claim.
  21. Maggan A
    Barbara i have lost 15 kilos in ten months just by eating eggs, meat, butter and full cream - everyday - and no more exercise than before. I recommend everyone to try LCHF It is the best way to loose weight and win health - a win win situation ;-)
  22. Cait
    There's something called nature verses nurture; the natural bred instincts of an animal, like a cat burying its crap, verses a nurtured trait that doesn't occur instinctively, like making said cat crap in a box.

    When kids are little, they're sponges and people know that very well, especially with eating habits. I'm from California from a smaller family and we have no "family dishes" or "family traditions", however moving to the Midwest I saw people who had these grease-laden family dishes they considered comfort food (one included two entire sticks of butter for a meal that fed like six people. Ew.). Most importantly tho is something most our dads did and how it affects us. Kids wanna be like daddy all the time, so when it comes to meal time, daddy would have a first serving then second and possibly third. Junior tries to keep pace. When junior can't finish then daddy just mops up and cleans off the kids plate.

    When said kid grows up with a nurtured trait of over-eating based on what he saw as a child (since it IS the nature of a child to learn from its parents for survival), they have kids and the nurtured over-eating cycle continues. This had probably gone on for 3-4 generations so people consider it to be "normal" or assume they have a genetic condition since their whole family is overweight or obese. Their whole family (the larger and closer-knit the higher the rate) have nurtured this over-eating trait for generations so now they don't even realize it. Give 'em a scooter so they can continue to eat foods high in saturated fats, sugars carbs and then bitch about how they got fatter.

    Most people in these scenarios I've noticed must've never been given healthy options as children; my niece from a young age would always want some of my fruit or vegetables. No one TOLD her to eat them, she just saw them, was curious, and liked it. Normally her parents don't give her many raw fruits and vegetables (common trait in the USA today since that takes "time and effort" in this instant gratification society). So as adults these people are adverse toward fruits and vegetables; I even have a friend who flat-out refuses any form of vegetation, even a leaf of lettuce on his burger.

    Our ancestors needed foods high in sugar and fat because in lean times where prey was scarce and foraging difficult, they needed those high-calorie foods to give them energy. In our first-world nation here, there's not so much of any "lean times", with the government even feeding our poor through various food stamp programs so there is no period of "whoops no food for anyone". We have so much in our grocery stores that it rots on the shelves. So we don't NEED those fatty, sugary foods, which just gets turned into fat as you sit at your computer at your desk for eight hours a day, moving only to use the bathroom.

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