What it is
Hundreds of times sweeter than sugar, with no calories — engineered to hit the sweetness receptor and nothing else. Some are over a century old (saccharin, 1879), some recent.
Why your biology objects
Sweetness with no glucose behind it uncouples taste from nutrition — your gut and brain prime for energy that never lands, and emerging work links some (sucralose, saccharin) to shifts in the gut microbiome and glucose tolerance. Beyond the biology: your taste calibration recalibrates to industrial sweetness, so real food stops registering as sweet at all.