> Humans are bad at lipogenesis: we can only convert tiny fraction of the carbs into fat.
Because historically food is scarce or difficult to obtain, in general organisms develop mechanisms to make good use of it: when excess food ("energy") is available, it is stored rather than wasted.
This is also true in particular for mammals, and for humans. It's quite obvious that humans are very effective at storing excess energy.
It is said that sumo fighters maintain their body mass (muscle + lots of fat) by eating rice (i.e. carbohydrates) and protein.
Lipogenesis (fat generation from carbohydrates) takes place mostly in the liver.
"Excess acetyl CoA generated from excess glucose or carbohydrate ingestion can be used for fatty acid synthesis or lipogenesis."
Nope. If humans eat both carbs and fat (most of us do), the excess calories of fat goes mainly into the storage (or plaques to your arteries), while the carbs are used in the sort term (converted into glucose).
> Lipogenesis is mostly derived from carbohydrates and is a relatively minor contributor to whole-body lipid stores, contributing 1–3% of the total fat balance in humans consuming a typical diet.
The human body doesn't need to store excess calories. It could store the excess calories or it can excrete energy through urine(glucose, ketones)
Or it can ramp up metabolism, there are many scenarios. Not all lead to adipose tissue growth. Why not muscle growth, which is somehow always overlooked in these discussions.
Funny enough adipose tissue and muscle growth are both through hormones. If testorone and hgh are high then muscles growth will prioritised over adipose tissue.
People with type 1 diabetes have figured out how to stay thin after eating copious amounts[0]. They won't inject themselves with insulin. Unhealthy, sure, but they won't store calories, as adipose tissue (fat cells) remain inactive, even though blood glucose is dangerously high.
Just looking at calories is simplification, and is just for general guidance.
Because historically food is scarce or difficult to obtain, in general organisms develop mechanisms to make good use of it: when excess food ("energy") is available, it is stored rather than wasted.
This is also true in particular for mammals, and for humans. It's quite obvious that humans are very effective at storing excess energy.
It is said that sumo fighters maintain their body mass (muscle + lots of fat) by eating rice (i.e. carbohydrates) and protein.
Lipogenesis (fat generation from carbohydrates) takes place mostly in the liver. "Excess acetyl CoA generated from excess glucose or carbohydrate ingestion can be used for fatty acid synthesis or lipogenesis."
https://courses.lumenlearning.com/suny-ap2/chapter/lipid-met...
The conclusion being: "Humans are great at lipogenesis. That's how we store excess energy."