o eat or not to eat
Your Health - Dr. Gita Mathai
We need nourishment to survive. Our body signals to us when we need food, our stomachs rumble when we feel hungry and, if the deprivation has been prolonged, we may even feel "faint" - signalling that blood sugar levels are falling.
An empty stomach secretes a chemical called ghrelin. This stimulates the appetite centre in the hypothalamus (a part of the brain). Unfortunately, even when you do not really require food, seeing the photo of a delicious-looking dish or actual food (say, in a shop window) or the tantalising smell of cooking can trigger the release of the hunger hormone, ghrelin. That why the fast food and aerated beverage advertisements on TV are so successful.
The message conveyed by ghrelin is often irresistible. People eat even when they are not really hungry. This is because ghrelin also works on "reward centres" in our brain, the same sites that are stimulated by alcohol, tobacco and addictive drugs like cocaine. So whenever we eat, we feel good and mood is elevated. That means the next time someone says they are addicted to chocolate, you'd better believe them.
The biochemical signals for appetite and satiety are complex. As hunger causes the blood sugar levels to drop, the pancreas releases glucagon, and the brain releases neuropeptide Y. As soon as we eat, and the blood sugar levels go up, our fat cells produce leptin and our brain proopiomelanocortin (POMC) - both appetite inhibitors. Some of these signals reach the brain via the nervous system and the blood carries others there. If we listen to our bodies, at this point we should theoretically stop eating.
Unfortunately there is a time lag in the signals and our response to them. By the time we realise and respond, it may already be too late and we have overeaten. This is particularly true of sugary snacks made from refined flour as they are digested rapidly. Plants and fruits take longer to digest. The chances of overeating are therefore reduced.
Children have well formed appetite centres practically from birth. If overfed (very easy to do with artificial feeds), the infant may refuse to feed or regurgitate. As the child becomes older, there may be a mismatch between how much the parent feels the child should eat and the amount actually consumed. If we make a fist with our hand (at any age), that is roughly the size of the stomach. Based on that, it is possible to calculate how much a child can be expected to eat.
Out of love and affection, we can force-feed children. Then their appetite centres get reset (sometimes permanently) at higher levels. Also, by giving fast food, there is a mismatch between amount consumed, caloric intake and requirement. This is clearly seen in our present day epidemic of childhood obesity.
Some children are picky eaters and will not eat the healthy food placed in front of them. Mealtimes become contentious and stress-filled. To avoid this
♦ Do not substitute milk or snacks for meals
♦ Do not begin or end the day with milk
♦ Do not put the child to bed with a feeding bottle
♦ A child over the age of 1 needs only 400ml of undiluted milk per day.
In the case of adults, loss of appetite may occur normally because of smoking, increasing age, pregnancy or thyroid disorders. If there is no obvious reason for loss of appetite, investigations need to be done.
There is really no safe drug that can be used long term for appetite suppression and weight loss. Eating food slowly, savouring it, increasing consumption of fruit and vegetables, cutting off snacks and exercising regularly is the only proven path to follow.
Dr Gita Mathai is a paediatrician and author of Staying Healthy in Modern India. Mail your questions to yourhealthgm@ yahoo.co.in
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