In addition to regulating food intake, body mass, and reproductive function, the peptide hormone leptin also affects angiogenesis, lipolysis, pro inflammatory immune responses, and embryonic development. The obese (ob) gene produces leptin, which binds to and activates its cognate receptor, the leptin receptor (LEP-R), after being synthesized and secreted by fat cells in white adipose tissue. The distribution of LEP-R promotes the pleiotropic effects of leptin and is essential for controlling body mass via a negative feedback loop between the hypothalamus and adipose tissue. Increased total body mass, overnutrition, and decreased satiety are the hallmarks of leptin resistance. This often results in obesity, which lessens the therapeutic benefit of exogenous leptin. Combining leptin sensitizers with leptin therapy may thus aid in overcoming this resistance and, as a result, obesity. This review looks at new information on leptin, its involvement in obesity, and its potential for treating obesity that has been gathered from research on humans and animals.