They're not random people though, especially Raymond Peat. There's research in those links. They literally talk about research in laymens.
What causes someone to not metabolize it property?
Damaged mitochondria, as a result from prolonged stress (excess weight, elevated FFA, PUFAs, estrogens, endotoxin, lack of sufficient light, over exertion, infection, trauma), not carrying out oxidative phosphorylation but instead trapping glucose at glycolysis ending in lactic acid (another stressor). Too much of any of these stressors bombards the liver and you end up with a sluggish liver that can't properly utilize fructose, and glucose to a lesser extent. Now you have varying degrees of insulin resistance and your blood markers are probably shot. All this is part of a positive feedback loop.
WADA banned Mildronate because of how potent it is at reverses mitochondrial damage and how it inhibits the use of fatty acids for energy during times of stress.
You're generally in great condition if your thyroid and liver is straight. Sugar won't be a problem.
I've run a diet where my >300g carbs were all sugar sources and took before/after blood tests. Never looked back. I still throw in glucose-dominant sources around exercise.
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There's more resources if you want.
