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Comment by rand_r | Hacker News Reader

“Sugar”, like “drugs”, is too general a term to use in a discussion on health. Glucose and fructose, both forms of sugar, are metabolized differently and have different health effects.

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People spend far too much time discussing the specifics, like glucose vs. fructose. Then they eat 8500 kcal/day but eat the "right" sugar and they're supposedly healthy. It's easier to care about fancy things rather than the basics.

Physics dominates everything, first and foremost. Thermodynamics governs diet through energy conservation laws that run the universe. That's rule #0. Everything else is maybe 20%. Human biology does not trump the laws of nature.

Physics dominates, but it’s often too simple a model to be useful in diet planning. When you run things through the filter of the an incomprehensible machine like the Human brain and metabolic and hormonal pathways the system gets much more complicated and useful.

The non-caloric fibre content of food is vital to gut flora, whose importance we’re still discovering.

Different foods affect hunger differently. High fat foods are more satiating that sugar.

The body isn’t a bucket, it’s a donut which has the capacity to absorb some food through internal walls while the food slips through very slowly. If you drink a bottle of oil, you won’t get fat. You’ll just have very runny and uncomfortable stool for a while.

Our body functions predominantly on ATP, not on glucose or fructose or fat or protein. ATP gets generated from those other macromolecules in pretty complicated biochemistry. You're definitely right that thermodynamics governs everything, but it governs it at the ATP level and not at the macronutrient level. Those additional layers of abstraction distort the whole calories in-calories out math.

Eating the "right" thing is more important than eating the "right" number. Consider eating 800 calories of protein versus 800 calories of alcohol (also technically a macronutrient). You're going to metabolize each differently, and you'll probably feel better eating the former than the latter. This is obviously an extreme example, but the point is that things that you eat affect your body in ways beyond that magic calorie number.

I can assure you, I feel a lot better after 800kcal worth of alcohol (about 3 beers) than after 800g of protein (a small chicken).

"Sugar" usually means sucrose which contains both glucose and fructose. They do have very different effects and fructose is much worse. But in the majority of products you find both together. Glucose (aka dextrose) is much less sweet and used in things like energy drinks. Fructose on its own is more sweet than sucrose and used in "naturally light" products (same sweetness, few calories, no artificial sweeteners). But in an average intake you're going to find glucose and fructose in roughly equal amounts, I think.

In the US at least, if an ingredient label says "sugar," it means sucrose. The sucrose molecule is broken up almost instantly in the digestive tract, and enters the bloodstream as a 50/50 mixture of glucose and fructose.

Sure but the effects aren't all that different.

Very different; glucose is metabolized by all cells in the body; fructose only by the liver.

Fructose isn't good for you (or sucrose 50% fructose, high fructose corn syrup 42%-65% fructose etc) https://www.youtube.com/watch?v=dBnniua6-oM

But its sweeter than glucose; and has side-effects like switching of appetite suppression and prolonged exposure does similar damage to the liver as alcohol. Glucose doesn't do that.

They actually are quite different. Glucose is directly usable by every cell in your body, whereas fructose has to be processed by the liver. There are no adverse health effects from taking pure glucose.

Here is a good video explaining it in more detail: https://youtu.be/dBnniua6-oM

> There are no adverse health effects from taking pure glucose.

Most people shouldn't be taking glucose. People should get their energy from food so that they get the nutrients and fibre with it. For most people taking glucose means either you'll get too much energy (and get fat) or not enough nutrients from real food.

On top of that it causes a strong insulin response which will decrease insulin sensitivity.

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