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Comment by scoot | Hacker News Reader

Nothing to do with the fact that they are 90% sugar?

Yeah this sounds like a something I'd read in a keto book I just read. High carbs -> poor insulin regulation, preventing the burning of fat and creating weight gain, plus various other pressures on the body which result from that.

I thought this too, but I've also seen speculation that fructose specifically triggers the body to be more inclined to store blood sugar as fat. If you think about it you can imagine an evolutionary just-so story for it. When protohumans encountered fruit, it was usually in a large quantity that couldn't be easily stored. Best to gorge and get chubby for later.

It largely has to do with different metabolic pathways for fructose vs glucose. Glucose can be metabolized in many places in the body, including directly in your muscles (glycogen) whereas fructose can only be metabolized in the liver.

Hummingbirds adapted to use fructose for energy production just like glucose:

> Now new research from the University of Toronto Scarborough shows they are equally adept at burning both glucose and fructose, which are the individual components of sugar; a unique trait other vertebrates cannot achieve.\

> From an evolutionary perspective the findings make perfect sense, says Welch. Whereas humans evolved over time on a complex diet, hummingbirds evolved on a diet rich in sugar. "Hummingbirds are able to move sugar from their blood to their muscles at very fast rates, but we don't yet fully understand how they are able to do this," he says.

https://www.sciencedaily.com/releases/2013/12/131205165823.h...

> Hummingbirds adapted to use fructose for energy production just like glucose.

And fish evolved to respirate oxygen from water…what’s the point?

Only dried fruits may be 90% sugar. Most fresh fruits are mostly water, followed by sugar, fiber, minerals and other things. They may be richer in sugar on a comparative scale (because we cultivated sweeter varieties), and some of them may have a high glycemic index.

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