'I just had something to eat. I shouldn't be hungry but I want to eat'; 'I can't eat any more of that food but I will eat more of this one, my favourite'; 'I know I should not be eating but I can't stop myself'; 'I am hungry all the time'; 'At some time of the month, I am out of control with cravings' and 'My stomach is always growling'. These are just some of the popular statements, associated with hunger which we hear all the time.

Hunger is an intricately controlled mechanism involving the brain, organs such as the liver and various hormones. Why are some individuals hungrier and hungry more often than others? Also, why do some people need larger amounts of food to curb their hunger? Our gender, body fat, activity level, health and medication are just some of the determining factors.

Controlled by the brain

The brain is an important centre, specifically the hypothalamus, in controlling eating. Damage to this area of the brain in animals and humans can create voracious eaters and subsequent obesity. On the other hand, damage to specific areas in the hypothalamus can result in reduced food intake leading to wasting. It is known that many signals found in the stomach and intestines are also found in the brain. These signals can serve to stimulate or inhibit food intake.

The hormone ghrelin has become important in recent debates on hunger and eating. This hormone is produced by the stomach lining, the pancreas and the brain. One of its roles is to stimulate appetite. Its level increases before a meal and decreases thereafter. The level of ghrelin is said to be reduced in some bariatric surgery resulting in reduced appetite.

A hormone that works in an opposite way to ghrelin is liptin. It has the ability to regulate the intake and expenditure of energy. It is produced by fat and other cells. The level of leptin produced in the body tends to be proportional to the body-fat level. It has receptors in the brain which regulate our intake by signaling that we are full.

Fructose consumption

Studies show that a very low calorie intake can lower leptin levels, causing a counterproductive problem of slowing down the satiety signal. Obese people tend to have very high circulating levels of liptin and tend to be resistant to its effect. Therefore, they do not receive the signal, on a timely basis that they are full.

Studies have also shown that high fructose consumption can also lead to liptin resistance and obesity in rats. Studies are now examining the role of insulin and liptin in glucose consumption, as it is believed that fructose consumption produces less circulating liptin, thereby increasing consumption before the satiety signal is received.

Insulin's role

Insulin also regulates hunger. When it is low, it signals the desire to eat. A down side in people with diabetes, who tightly control their blood sugar levels, is that they can have frequent needs to eat and are at risk of increased body fat.

There are other receptors in the brain called neurotransmitters which can also control appetite and are usually manipulated by pharmacological agents.

We do not yet know if it is the chicken or the egg that came first, but we can try to control our weight and that of our children by avoiding high intakes of fructose and large amounts of carbohydrates especially refined types. In this way, we prevent the violent spikes in blood sugars and the lows which continue the vicious cycle of hunger.

Rosalee M. Brown is a registered dietitian/nutritionist who operates Integrated Nutrition and Health Services; email: yourhealth@gleanerjm.com.