The substance, which occurs naturally in the body, could pave the way for a new class of dieting drugs that help people shed pounds without distressing side effects.
The idea would be to stop us eating purely for pleasure instead of from hunger.
It could also be used to treat alcohol and drug abuse, researchers at Manchester University say.
The chemical – called hemopressin – works by affecting the reward centres of the brain that light up when someone enjoys a comforting snack or cigarette.
Tests have shown that hemopressin blocks these areas of the brain, reducing the reward from eating.
A synthetic product called Rimonabant, which acted on the brain to reduce hunger, was developed six years ago and marketed as an anti-obesity treatment.
But it appeared to increase the risk of depression and suicidal thoughts and was withdrawn from the market.
Dr Garron Dodd, co-author of the latest findings published in the Journal of Neuroscience, believes naturally-occurring hemopressin can suppress hunger without the side effects.
In tests, laboratory mice fed hemopressin ate less food.
However, the chemical had no other impact on their behaviour. An identical group of mice given a synthetic form of the chemical also ate less, but suffered side effects such as increased grooming and scratching.
‘We now plan to investigate this further,’ Dr Dodd said.
He added: ‘While our findings are an indication of safety, this cannot be immediately extrapolated to humans.
‘This discovery does, however, offer new insights into how the brain controls appetite and opens new avenues by which to manipulate this brain circuitry and aid the development of anti-obesity treatments.’
The finding could lead to drugs that stimulate the brain to produce more hemopressin, he said.
Orlistat, the most popular obesity drug, prevents fat absorption and is taken by hundreds of thousands of people.