Leptin is a hormone that is primarily made by fat cells. It has a function of reducing appetite by binding to receptors in the hypothalamus which is located in the brain. If the receptors of the hypothalamus become desensitized to leptin then hunger increases leading eventually to metabolic disorders such as dysglycemia and obesity.
Leptin Ups and Downs:
Emotional stress increases leptin which is why we lose weight during times of anxiety (only to gain it back when we feel better).
Exercise reduces leptin which means exercise can make us hungry; dietary changes have always been more effective for weight loss than exercise (or at least exercise by itself).
Insulin increases leptin. Dysglycemia (carbohydrate metabolic disorders which cause spikes in insulin) increases leptin to the point of both insulin resistance and leptin resistance which is why we get fat and more hungry. The cells stop taking in fuel and the brain ignores the signal to stop eating.
Intermittent fasting, or time restricted eating, decreases leptin...but be careful how you fast or you'll set yourself up for a binge. Just make sure you're getting nutrient rich foods (lots of veggies).
The role of leptin in management of fat deposition seems clear but more research is needed to fully understand its function and where else in the body it is produced and received. For now, if you're struggling with your weight consider reducing your daily carbohydrate intake to below 80 grams and spent more of your time not eating at all.