The evidence is convergent. Multiple independent sources reach the same conclusion, the underlying mechanism is well-characterized, and even the field's most cautious voices treat it as worth doing.
These AgRP neurons are what caused that, in fact so much so that if you eliminate or kill these neurons, which has been done in experimental mouse models in the laboratory, but also there are humans that have lesions or neurotoxic effects on these AgRP
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Now, there are signals coming back from the body to inform the brain about presence of different levels of nutrients. And that generally comes from three sources. First of all, is body fat. The more body fat we have, the more we secrete a hormone called leptin, L-E-P-T-I-N, leptin from body fat, leptin goes to the brain and suppresses appetite.
And you have a class of neurons called the AgRP neurons. The AgRP neurons are the ones that stimulate feeding, and they create a sort of anxiety or excitement about food, can be positive anxiety, or it can be negative anxiety.
if you eliminate or kill these neurons, which has been done in experimental mouse models in the laboratory, but also there are humans that have lesions or neurotoxic effects on these AgRP neurons. And what you find is that they don't want to eat. They essentially become anorexic, meaning they don't want to ingest food. They have no appetite for food whatsoever.
what the neurons were doing was predicting the mouse looks at at the at the food it looks at how palatable it is imagines how hungry the mouse is how accessible it is and then within a few seconds these neurons predict how much food the mouse is going to eat in the forthcoming meal
and you can show this in very simple by very simple analysis in which you you give the mouse different foods and you look at how much these arrp neurons drop when the mouse sees and smells the food and then you plot that again so this this drop happens in 3 seconds 4 seconds something like that then you look at how much does the mouse go on to eat in the next 30 minutes and you can just draw a straight line
what he found was really surprising I remember that when he made this discovery basically him running into my office and saying Zack I I gave the mouse the piece of food but the weirdest thing happened the neurons shut off almost immediately
so these hrp neurons there are a few thousand neurons at the base of the hypothalamus so basically the the the most ventral the most bottom part of the forbrain um so tiny population of cells but outsized importance for the control of feeding Behavior so if you stimulate these cells in a mouse or a rat that's not hungry um the animal will voraciously eat like get starving uh if you silence these cells U animals will starve to death so you can basically give them food they just won't eat it voluntarily until basically they you have to euthanize them because they're uh they've lost so much weight