DIET Talk - YOU ARE WHAT YOU EAT – Why?

Appetite

Appetite is the desire to eat food. The appetite centre is situated in the brain and regulates the amount of energy intake (from food and drink)) needed to keep the bodies metabolism working normally. When the metabolism is increased e.g. through exercise more food is needed and vice versa. Hunger is the physical sensation experienced when blood sugar levels start to fall because the liver stores are being depleted. The two terms are interrelated.

Steady state

In the steady state, that is, in somebody who is neither losing nor putting on weight, the intake of energy through food/drink will balance the utilisation of energy by the body. Thus a fat and a thin person, leading similar life styles will have similar needs for food to keep to a steady state and one will remain fat and the other thin. On the other hand, a physically more active person of the same weight as a sedentary person will need a higher intake of calories in order to maintain the weight in the steady state.

Control of appetite

Appetite is controlled through the action of many hormones and other substances mostly in the brain, nerves and gut. Their cooperation ensures that we eat when we need to. When one or more of those mechanisms fail, one overeats or loses appetite and therefore gains or loses inappropriate amounts of weight. Unplanned or unexplained weight loss is usually due to a medical disorder. Obesity however, is much more commonly due to habitual overeating of high calories foods and a sedentary file.
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Why do we put on weight?

Every molecule of energy containing foods not needed, is stored. Thus every molecule of sugar, in whatever form it is ingested, will be stored as fat if taken in excess of what is needed. It is said that a daily intake of even a half a biscuit in excess of what the body needs as energy will result in an extra stone in weight within 6 months.

How to lose weight healthily?

If one eats less than is needed for providing appropriate amounts of energy for maintaining the body metabolism, once the glucose stores in the liver (glycogen) are used up (this occurs within a few hours of starvation) the body will start to utilise it’s own fat for energy. Thus, in order to lose weight, the intake of energy must be less than the expenditure of energy, the balance being made up from one’s own fat. Further, if the reduced calories intake is combined with increased calories expenditure as with exercise, the fat utilisation will be speeded up. However, there are dangers in this if the weight loss is too sudden or drastic because high fat utilisation also leads to the production of certain acids (ketones) which are broken down slowly and which can, if they accumulate too much in the body cause medical problems including heart failure.

The healthiest and safest way to lose weight is to change one’s dietary habits and eat a consistently moderately less calorific diet, in smaller quantities as well as combining it with foods higher in fibre, vitamins, minerals and proteins and doing more exercise. This is the hall mark of ‘healthy living’. For the effects on weight reduction to have a lasting effect, this healthier living has to become the new habit, replacing the old. For many people this is very hard and they go from one crash diet to the next one with rebounds in weight when they stop. Further, as metabolism also slows down with crash diets, in time, the diets become less effective.

Dr Yvette Lolin, Clinical Advisor
FRCPAth, PhD
Consultant in Metabolic Medicine and Chemical Pathology