https://www.nature.com/articles/nrn.2017.168
When our fat cells (adipocytes) are full they release a hormone called leptin which then travels to the brain and makes us feel full. This review looked at how this hormone changes in people with obesity. They found that the brain of people with obesity is less sensitive to leptin, meaning that when their fat cells are full and releasing leptin, their brain does not respond and so will not make them feel full. This lack of response to leptin can be called leptin resistance.
