Pituitary News, Issue 26 - Winter 2003.

Energy balance in humans is a finely regulated process. There has been much research into what controls appetite and body weight and the fact that no-one has yet come up with the definitive answer tells us that the picture is very complicated. We all know people who apparently sail through life not thinking about what they're eating or drinking and whose weight never changes. This must be a potent argument for the fact that there is some physiological control of appetite and body weight of which we are neither conscious nor aware. So what happens when this unconscious control goes wrong?

Pam Dyson
Dietician specialising in Endocrinology, Radcliffe Infirmary, Oxford.

How does the brain control appetite?

There is now good evidence that there are a series of chemical messages sent to the appetite centres in the brain from all parts of the body. These tell the brain about the size of body fat stores, blood glucose levels and the presence (or absence) of food in the gut. The messages form an 'appetite cascade' which helps the body to make sense of current energy levels and dictate how much or how little needs to be eaten. The appetite centres in the brain are located in the Hypothalamus, which is next to the Pituitary gland. Damage to these centres can occur in patients with tumours in the region of the hypothalamus (for example, Craniopharyngioma) and can result in disturbed appetite and weight gain.

What about other factors affecting body weight?

Occasionally, changes in body weight are caused by hormonal problems. An underactive thyroid, for examples, slows metabolism. As a result, fewer calories are "burned off" and, I food intake is maintained, there is a gradual weight gain. Increased steroid levels in Cushing's syndrome cause appetite stimulation and changes in metabolism which also result in increased weight. Unfortunately, hormonal problems are not the whole picture. Obesity has trebled in this country over the past twenty years and this is a direct result of changes in lifestyle, especially changes in physical activity. We are eating more high-fat foods and taking much less exercise that we did even ten years ago and this has had a major impact on body weight. This is a positive message as it means that deliberate changes in food intake and exercise can help reduce body weight.

So how can I lose weight?

There is no quick and easy solution to weight loss. Most crash or fad diets (like the cabbage soup diet, grapefruit diet, Atkins diet) are not nutritionally balanced and encourage rapid weight loss, which is accompanied by equally rapid weight gain once the diet is finished. The best way to lose weight is to increase physical activity and reduce the amount of food eaten. It is better to make small changes that can be kept up over time rather than making huge changes that have a big influence on lifestyle and which are usually difficult to maintain long-term.

Practical tips for weight loss

• Be realistic! Increase physical activity gradually by more walking, housework or gardening. It's not necessary to leap around a gym dressed in pink lycra or run the London marathon to feel the benefit of exercise.
• Try to eat a low fat, low sugar diet with plenty of fruit and vegetables. If you are not sure of the kind of foods you should be eating then ask your doctor for a referral to a State Registered Dietician.
• Remember - small changes give big benefits over time. Eating 100 calories (one slice of bread or two biscuits or one small glass of wine) a day less than your body needs will cause a weight loss of 10lbs over a year.