Articles
The nutritional understanding behind obesity
Overweight and obesity is increasing. It occurs when energy intake exceeds energy expenditure. Even if one has a slow metabolism or has an under active thyroid, it still comes down to the same equation. If you eat more than you are burning up, you are going to put on weight.
In Australia two out of every three men and one in two women are overweight or obese. At least twenty percent of children are showing prevalence to overweight or obesity.
There are three main causes of obesity.
Excess energy intake
This is associated with just eating too much or consuming too much fat and alcohol. Fat and alcohol are very concentrated sources of energy so it is easy to have a very high intake of kilojoules in what appears to be a very small quantity of food or drink.
Low Activity Levels
It appears that the decrease in daily activity at work and leisure is now a major cause of overweight and obesity. Some people may walk, swim and cycle but still be very inactive as they sit at a computer or desk all day. It is difficult for them to burn up the kilojoules they consumed.
Genetic predisposition to obesity.
There are now four single genes that have been reported to be associated with obesity. This is probably not applicable to the majority of over weight people who simply eat too much, are inactive or have slowed their metabolism through yo yo dieting.
The content of the diet makes a difference
It is better to consume more carbohydrate than fat or alcohol
Fat and alcohol are more concentrated forms of energy in comparison to carbohydrate. Fat gives 36 KJ or 9 Calories per gram and alcohol gives 28 KJ or 7 Calories per gram. Carbohydrate only gives 16 KJ or 4 calories per gram. It is less energy dense. A slice of bread has 70 calories (236 kilojoules), the same as two teaspoons of butter. Foods containing fat is less filling but more energy dense, often leading to over consumption.
Fat is easily and efficiently converted into fat storage.
The body is very efficient in turning the fat in food into storage fat in the body with a loss of only 3% of energy. On the other hand excess carbohydrate has a loss of a 23 % energy in converting excess into fat storage.
There is a preferential order of use of energy producing nutrients.
The body metabolises alcohol then carbohydrate then protein and finally fat.
Alcohol
If the alcohol intake is high, there is little or no chance of burning up the fat and very little chance of burning the carbohydrate. There is no capacity to store alcohol so the body oxidizes it and uses it as energy first.
Carbohydrate
The body can increase the energy expenditure of breads, cereals, grains, pulses, fruit, vegetables and sugars through oxidation when excess is consumed. This does not occur with fat. Carbohydrate balance can be maintained through storage as glycogen in the muscle and liver and through energy oxidation. Athletes store higher quantities of carbohydrate as glycogen and then utilize it for high-energy events.
Protein
Protein is necessary for building and maintaining muscle. The body has limited ability to store protein but can adapt to different levels of intake.
Fat
Fat is metabolised last. It is easy to store fat in the body and difficult to metabolise it once it is stored. Remember that alcohol, carbohydrate and protein will be used first.
How does obesity occur?
Weight gain occurs because you eat more than you burn up either in the short or long term. For example: going on holiday, being inactive and eating considerably more food may cause a weight gain of two or three kilos in a very short period of time. Other people eat a little more than they are utilising every day and eventually put on weight. Others binge eat, which leads to weight gain in the long term.
Why yoyo dieting does not work
Restricted kilojoule intake leads the body to think that it is being starved. When more normal quantities of food are introduced, more fat is deposited with the re-feeding than otherwise would have occurred. It has also been found that on very low food intakes, people become less active as they don’t have the energy to exercise.
Why do we like fat?
Studies of obese people have shown a preference for high fat foods. Fat has a particular pleasant mouth feel as well as being easy to chew and swallow. It is readily consumed, it has a high-energy content and it comes in very flavoursome packages such as chocolate, chicken skin and fat on chops. High fat intake makes it easier to exceed energy requirements, increasing fat stores, causing weight gain.
High Carbohydrate Diets versus High Fat diets
The resting metabolic rate is responsible for 60 – 70% of the total energy expenditure. This is a measure of how much energy it takes just to perform functions such as breathing, regulating body temperature and digesting food. When excess carbohydrate is eaten there is a 10 to 40% increase in resting metabolic rate over a 24 hours period compared to an 8% increase when excess fat is eaten. Habitually high carbohydrate eaters such as vegetarians have been shown to have 11% higher resting metabolic rate compared with non-vegetarians.
Weight control is easier with low fat, moderate carbohydrate intakes.
Bread, cereals, pasta, noodles, rice, pulses, fruits and vegetables are all excellent sources of carbohydrates and have less than half the kilojoules of fats. They are less likely to be converted into body fat. Replacing fat, especially saturated fat with carbohydrates can reduce the risk of many diet related diseases while providing appetite satisfaction, fibre and nutrients.
Recipes
Red Lentil Soup : A complete meal when combined with crusty bread and salad.
Added to site on : Monday, 24 February 2003