Outline the hormonal memchanisms involved in the control of eating behaviour (6 marks)

Ghrelin and leptin are the two main hormones associated with the control of eating. Ghrelin, which is released from the stomach, activates the hypothalamus and increases a person's appetite. The levels of this hormone increase rapidly before eating and then decrease slowly over a period of 3 hours after eating a meal. Ghrelin also controls how quickly a person becomes hungry. Wren et al. conducted research into the role of ghrelin and found that participants given an intravenous ghrelin solution ate almost 30% more food at a free-choice buffet than those given a saline solution, supporting ideas about the role of this hormone in controlling eating behaviour.

Leptin, known as the 'energy expenditure hormone', is associated with weight control, as well as the control of eating behaviour. Leptin is produced by fat tissue. From there it enters the bloodstream and travels to the brain to decrease appetite. The role of this hormone is confirmed by cases of leptin resistance. This condition is very common in overweight or obesity problems, as the hormone isn't able to reduce appetite, leading to weight gain.