Leptin is a hormone secreted from fat cells that helps to regulate body weight. The name leptin is derived from the Greek word 'leptos' meaning thin. It is sometimes referred to as the 'Fat Controller'.

Alternative names for leptin

There are no other names used for the hormone but the gene, which encodes leptin, is known as the 'ob' gene.

What is leptin?

Leptin is a hormone released from fat cells in adipose tissue. Leptin signals to the brain, in particular to an area called the hypothalamus. Leptin does not affect food intake from meal to meal but, instead, acts to alter food intake and control energy expenditure over the long term. Leptin has a more profound effect when we lose weight and levels of the hormone fall. This stimulates a huge appetite and increased food intake. The hormone helps us to maintain our normal weight and unfortunately for dieters, makes it hard to lose those extra pounds!

How is leptin controlled?

Because leptin is produced by fat cells, the amount of leptin released is directly related to the amount of body fat; so the more fat an individual has, the more leptin they will have circulating in their blood. Leptin levels increase if an individual increases their fat mass over a period of time and, similarly, leptin levels decrease if an individual decreases their fat mass over a period of time.

What happens if I have too much leptin?

Obese people have unusually high levels of leptin. This is because in some obese people, the brain does not respond to leptin, so they keep eating despite adequate (or excessive) fat stores, a concept known as ‘leptin resistance’. This causes the fat cells to produce even more leptin. This is similar to the way people with type 2 diabetes have unusually high levels of insulin, as their body is resistant to the effects of insulin. The cause of leptin resistance is still unclear.

What happens if I have too little leptin?

There is an extremely rare condition called congenital leptin deficiency, which is a genetic condition in which the body cannot produce leptin. In the UK, there are only about four families affected by this genetic condition.

Absence of leptin makes the body think it does not have any fat whatsoever and this results in uncontrolled food intake and severe childhood obesity. In addition, leptin deficiency may cause delayed puberty and poor function of the immune system. This condition can be well treated by leptin injections, which cause dramatic weight loss.

Last reviewed: Dec 2014