The new obesity vaccine, which uses the immune system to fight weight gain, was found to help mice reduce about 10 per cent of body weight four days after they have received it.
What is more, the animals were being fed on high-fat food -- suggesting the "flab jab" might allow people to eat badly yet stay slim, the researchers said.
"This study demonstrates the possibility of treating obesity with vaccination," said lead study author Dr Keith Haffer of US firm Braasch Biotech.
"Although further studies are necessary to discover the long-term implications of these vaccines, treatment of human obesity with vaccination could provide physicians with a drug and surgical-free option against the weight epidemic," Haffer was quoted as saying by the Daily Mail.
According to the scientists, the vaccine works by fooling the body's immune system into making antibodies against a hormone, called somatostatin.
Somatostatin -- which is made by the brain and the digestive system -- interferes with other hormones, leading to the metabolism slowing down and weight being put on. The antibodies stop it from working, the metabolism speeds up and the pounds fall off.
In the study, published in the Journal Of Animal Science and Biotechnology, it was found that the vaccine reduced body weight of the mice without affecting their normal levels of growth hormones.
The mice that shed 10 per cent of their weight after one jab were given a booster jab three weeks after the first which helped to keep their weight in check, the researchers said.
"The vaccination effects did not significantly reduce cumulative food consumption and was confirmed by residual anti-somatostatin antibodies in mouse plasma at the study's end," they said.
However, they cautioned that they were in early stage of their research and such a jab could take around seven years to hit the market.
Further research is also needed to look at the vaccine's effects in obese pigs and dogs before moving onto human trials, they added.