Metabolism. Our genetic make-up also underlies our metabolism, (basically how many kilojoules we burn per minute). Bodies, like cars, differ in this regard. A V-8 consumes more fuel to run than a small 4-cylinder car. A bigger body, generally, requires more kilojoules than a smaller one. Everybody has a resting metabolic rate. This is a measure of the amount of kilojoules our bodies use when we are at rest. When a car is stationary, the engine idles—using just enough fuel to keep the motor running. When we are asleep, our engine keeps running (for example, our heart keeps beating) and we use a minimum number of kilojoules. This is our resting metabolic rate. Our resting metabolic rate is the amount of kilojoules we burn without any exercise. When we start exercising, or even just moving around, the number of kilojoules, or the amount of fuel we use, increases. However, the largest amount (around 70 per cent) of the kilojoules used in a 24-hour period are those used to maintain our basic body functioning. Since our resting metabolic rate is where most of the kilojoules we eat are used, it is a significant determinant of our body weight. The lower your resting energy expenditure the greater your risk of gaining weight and vice versa. We all know someone who appears to ‘eat like a horse’ but is positively thin! Almost in awe we comment on their ‘fast metabolism’, and we may not be far off the mark!
All this isn’t to say that if your parents were overweight that you should resign yourself to being overweight. But it may help you understand why you have to watch your weight while other people seemingly don’t have to watch theirs.
So, if you were born with a tendency to be overweight, why does it matter what you eat? The answer is that foods (or more correctly, nutrients) are not equal in their effect on body weight. In particular the way the body responds to dietary fat makes matters worse. If you are overweight it is likely that the amount of fat you burn is small, relative to the amount of fat you store. Consequently, the more fat you eat, the more fat you store. Although this may sound logical, the ‘eat-more, store-more’ mechanism does not exist for all nutrients.
Amongst all four major sources of kilojoules in food, (protein, fat, carbohydrate and alcohol), fat is unique. When we increase our intake of protein, alcohol or carbohydrate the body’s response is to burn more of that particular energy source. Sensibly, the body matches the supply of fuel with the type of fuel burned. One of the fundamental differences between fat and carbohydrate is that fat tends to be stored whereas carbohydrate has a tendency to be burned. It is worth noting at this point that if your carbohydrate intake is low, it may reduce the amount of kilojoules you burn each day by 5 to 10 per cent While you may not have been born owning the best set of genes, you can still influence your weight by the lifestyle choices you make. The message is simply this: if you believe that you are at risk of being overweight, you should think seriously about minimising fat and eating more carbohydrate.
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Many manufacturers now provide nutritional information on food packages. These may be useful in planning the diet for the person with diabetes.
Here are two examples of package labels:
1. An individual serving may be described.
Nutriment composition per serving one serve as described on packet
Protein 3 g
Fat 2g
Carbohydrate 15 g
Kcals 90
Kjoules 378
From this label one serve would be equal to one carbohydrate exchange.
1. The description may refer to a certain amount of the food. Nutrient composition per 100 g of prepared food.
Protein 4g
Fat 6g
Carbohydrate 22 g
Kcals 158
Kjoules 664
From this label l00 g of food would provide approximately 1 1/2 carbohydrate exchanges. If an average serve weighs approximately 30 g, then it will provide 1/2 carbohydrate exchange.
This information helps you work out the number of carbohydrate exchanges per serve. Not all foods labeled in this way are suitable for regular use as they may have high sugar content. It is also important to read the ingredients labeling. Ingredients by law are listed in decreasing order. Inclusion of ingredients such as sugar, glucose, dextrose, and honey in large amounts may mean that the product should not be used under normal circumstances.
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