One of the substances produced by fat cells in our body is called leptin. If we have more fat cells, we are able to produce more leptin, and it plays a key role in regulating energy intake and expenditure, including appetite, hunger, metabolism and behavior. When leptin levels are high, animals behave as if they have a lot of nutrition, they will eat less, become more active and increase the activity of their immune system. On the other hand, leptin levels are low; animals will eat more and rest more because they need to conserve energy which allows them to dedicate energy to their immune system. However, animals with the obese gene do not produce leptin, which means they feel hungry, try to eat as much as possible, and try to conserve their energy by not moving much. Is it really true that animals stop eating when they have a high leptin level and start feeling hungry when they have a low leptin level? As a result of online research, I found an article published by M. Flavia Barbano and Martine Cador who are studying at the University Victor Segalen Bordeaux in France. Furthermore, this report was carried out at the Neuropsychology Laboratory of the Victor Segalen University of Bordeaux. This diary used thirty-two rats and three experiences investigating the motivational, anticipatory and consumption aspects of feeding, it tested the appetite of a rat that was satiated by giving it its favorite food. The result is able to determine the authenticity of the Leptin theory using short-term and long-term power regulation. In the test, it took the investigators about a month, including switching the rats from the cage to the glass bowl, to get the result, and the research was successful... middle of paper... .eating the chocolate cereal instead of normal food. However, the result of the second test was not the main point verifying the authenticity of the leptin theory. In the third test, the researcher provided normal food to the rats and fed them until they were full, meaning the leptin level had been lowered. are high in rats and the message sent by the brain will cause the rats to stop eating and start becoming active. At that point the rats stop eating; the authors provided chocolate cereal which is the favorite food of the rats they were faced with when they contain a high level of leptin. Even though the rat still ate some chocolate cereal, after a few bites the rats could no longer continue. The rats' food cravings clearly decreased due to the low leptin level. Even when they presented leptin, it still played an important role in their appetite.