Bio Explanation of AN

• Anorexia is a serious illness that affects 10% of women and 5% of men
• Women in Western cultures are 5 times more likely to develop anorexia than males
• Around 1:20 sufferers die from the disorder with 1:5 committing suicide
• Criterion A, restriction of food intake, suggests that an individual must be less than 75% of their 'normal' weight to be diagnosed
• Purging is when a patient will prevent weigh gain or promote weight loss through vomiting, misuse of laxatives, diuretics & enemas
• Hypothalamus


  The hypothalamus is a part of the limbic system. It can be termed the 'feeling and reacting' part of the brain. One of the functions is to regulate eating and a malfunction here could explain both avoidance of food and binge eating due to the hypothalamus controlling appetite. It is also the feeling and reasoning part of the brain so can lead to anorexia patients feeling happy when they lose weight.
• The hypothalamus sends signals to other areas of the brain


  To tell us we are hungry
• Ghrelin


  The hormone ghrelin is produced in the stomach when we are hungry, so ghrelin levels typically rise before a meal and decrease afterwards and signals the hypothalamus that we are full. In anorexic patients, ghrelin levels are elevated as the person is starving. When an AN patient does eat ghrelin levels drop significantly, which could explain why people with anorexia find it difficult to put on weight as their hunger signals are not working correctly. In addition, if ghrelin cannot bind to the receptors in the hypothalamus due to brain lesions, the brain interprets this as the person not being hungry causing them to stop eating.
• Leptin


  Leptin is produced in adipose (fatty) tissue and travels through the blood to the brain. Leptin signals to the hypothalamus that we are full. You would expect people with Anorexia to have low levels of leptin as they have little fatty tissue, but their leptin levels are often high. Because they are starving, when they eat a small amount leptin is produced in high levels, sending a faulty signal to the hypothalamus that they are full, meaning they don't feel the need to eat more.
• A strength is that it is a reductionist way to provide a simple explanation that AN is due to malfunction of the hypothalamus in controlling hunger so it means that it is easier to predict who is likely to develop AN based on the activity of the hypothalamus and levels of ghrelin / leptin.
• A downside is that it ignores individual differences such as impact of social media as a cause of AN symptoms so dysfunction of the regulatory actions of the hypothalamus may not be the only explanation of what causes someone to develop AN.