Matt Franz : Zealous For Knowledge

The bitter truth about sugar


Dr. Robert Lustig joined Gabby Reese and Neil Gaiman in The Truth Barrel. Dr. Lustig is the author of Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity, and Disease. He also gave the viral talk Sugar: The Bitter Truth and is an expert in childhood obesity. In this interview, Dr. Lustig gives compelling reasons why eating sugar without fiber makes us fat, tired, and unhappy.


Before I get to my notes, I want to stress that I am not a doctor and don’t play one on the internet. I cannot vouch for the validity of Dr. Lustig’s statement’s. Below is my understanding of his arguments.



Willpower is a limited resource but your biochemistry is running 24/7/365. When your body tells you it is hungry, you are going to eat.


When doctors see an obese patient, they say, “You overeat and you’re a sloth. Of course you’re fat.” And it is true – they do overeat and they are a sloth. But these behaviors are symptoms of a biochemistry problem. To try to change behavior would be to treat the symptoms and not the cause.


70% of Americans are normal weight. Of these 40% are metabolically ill. They get the same diseases as fat people: type 2 diabetes, hypertension, cardiac problems, lipid problems, cancer, dementia. Because they are a normal weight, these people don’t think their problems are within their control.


Weight measures bone (more is better), muscle (more is better), subcutaneous or big butt fat (more is actually better), and visceral or belly fat (less is better). The bad stuff – visceral fat – is only about 4% of your total weight.


If weight doesn’t correlate well with metabolic disease, then what does? Liver fat. Dr. Lustig recommends using your waist circumference as a “back of the envelop” method of measuring your liver fat.


When you eat sugar (fructose) without fiber, it is absorbed early in your intestine and processed by the liver. Unable to keep up with the onslaught, the liver turns it straight into fat.


It’s not that sugar, in all forms, is toxic. We have evolved to like sugar for good reason: there is no acute toxin known in nature that tastes sweet. Sugar is natures way of telling us something is okay to eat. The gene for sugar sensitivity is conserved across all species.


The problem is that, in nature, sugar is always accompanied by fiber. Consider taking six oranges, juicing them, and drinking the juice. You’ll be able to easily finish the glass and be hungry for more. But if you sat down and actually ate all six oranges, you’d be so full that you’d be sick. The difference is the fiber. Fiber makes sugar consumption self-regulating.


When we eat fiber, it forms a gel that guides our food through our intestine. This causes our food to work through our intestine faster, which makes us feel full quicker. It also means that the food is absorbed towards the end of the intestine. Without the gel, it gets absorbed right away. Our gut bacteria also need to eat and they eat fiber.


Sugar is okay to eat so long as it is accompanied by fiber.



If you slice an apple in half and leave out, it will turn brown. The reason is that the fructose in the apple oxidizes. The same thing happens inside your body when you eat fructose: the oxidation process produces a free radical which can damage or kill cells. The result is aged or wrinkled skin.


Insulin’s job is to turn the sugar in your bloodstream into fat. The more sugar you eat, the more insulin you’ll have in your bloodstream.


Lets assume your body wants to burn 2,000 calories per day. If you eat 2,000 calories per day you should be perfectly fine. But if you eat 2,000 calories and have a high insulin level, some of those calories, say 500, will be immediately stored as fat. Those 500 calories are no longer available for the body to burn. When your body wants to burn 2,000 calories but only has 1,500, it feels starved. You will feel hungry and have low energy (you overeat and you’re a sloth).


If you eat more sugar you will only further increase your insulin level. Eventually you’re body will reach its limit for producing insulin. This is known as Type 2 Diabetes.


When you eat sugar, the “reward center” (nucleus accumbens) of your brain releases dopamine. Dr. Lustig calls dopamine the pleasure chemical and serotonin the happiness chemical.


Dopamine down-regulates its own receptors. Each time you get a shot of dopamine, a few dopamine receptors are turned off. To get the same rush, you have to increase the amount of dopamine each time. This means eating more fructose. These are the mechanics of addiction.


By contrast, serotonin does not down-regulate its own receptors. But dopamine down-regulates serotonin receptors. Dopamine release also temporarily blocks the brain’s ability to release serotonin.


If you seek pleasure (dopamine) you will end up unhappy (lack of serotonin).

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