Obesity is defined as an excessive accumulation of body fat. The prevalence of obesity is on the increase in the western world,
leading to a major health crisis as obesity has been identified as a major risk factor for diseases such as adult-onset diabetes,
heart disease and some cancers.
Obesity is largely related to lifestyle factors such as diet and exercise. However,
in rare cases, it may be related to a genetic defect in metabolism or may arise
as a result of certain disease states. Social and psychological factors also play
a role.
Lifestyle factors
High calorie intake
Weight gain occurs when someone consumes more calories than they burn off during
physical activity. The excess calories are then stored in tissue as fat.
There are three mechanisms in which the body burns calories:
- Through physical work and exercise
- Through the energy used by the body at rest (basal metabolism)
- Through the energy used to digest food (the thermic effect of feeding)
The reason some people gain weight more easily than others lies in the rate at which these normal metabolic functions operate, i.e.
the rate at which the body turns food into energy. People with a low basal metabolic rate tend to burn off calories slower and
therefore gain weight more easily. However, the exact cause of a low basal metabolic rate is still largely unknown and arises from
a variety of complex factors, including a inherited disposition.
Yo-yo dieting
People who have experimented with repeated fad and crash diets often lose weight only to find that they put it back on - with interest.
This may be because starving the body causes a slowing of the metabolic rate. When food consumption resumes, weight gain happens quicker
because the body has become less efficient in burning off calories.
High fat intake
- Studies have indicated that the amount of fat in a person’s diet may have a greater bearing on weight gain than total calorie/energy intake
- Carbohydrate and protein foods provide an immediate energy source for the body, and are converted to energy more quickly than fats
- Most fat calories are immediately stored in fat cells, thus adding to the weight and fat content of the body
- High fat consumption is a problem, especially in this age where the availability of high-fat processed foods and fast foods is increasing
High carbohydrate intake
- It is likely that excess carbohydrate intake plays an important role in the development of obesity. Carbohydrates which are not used for energy production are converted to and stored as fat. When carbohydrates enter the blood stream, the pancreas produces the hormone insulin. One of the functions of this hormone is to promote the uptake of glucose by cells. However, it also encourages the storage of fat
- Current evidence shows that weight gain is mostly linked to the total amount of calories (and fat) consumed rather than to the amount of carbohydrates consumed
- Simple carbohydrates such as those found in sugars, sweets, cakes and pastries are more likely to promote insulin secretion and fat storage, than complex carbohydrates such as pasta and whole grain foods. These foods produce a more moderate insulin response and less fat storage
- This issue has caused much confusion in consumers, who are bombarded with information advocating both high and low carbohydrate diets for weight loss. This area of research still remains highly controversial
Sedentary lifestyle
- Low activity levels also contribute significantly to weight gain. Exercise is essential for achieving energy balance as it helps the body to burn off excess calories from food
- People who do not engage in high intensity exercise at least three times a week are at an increased risk of developing obesity. The type and intensity of exercise needed differs between individual
- People who lead sedentary (little movement or exercise) lifestyles or have jobs involving little physical activity are also at an increased risk of becoming obese
Genetic factors
The “thrifty genotype”
The thrifty genotype (genetic type) is said to have developed during times of famine, as a survival advantage, to allow the storage of calories during
times of plenty. This fat-storage gene is suggested as an explanation as to why some people put on weight more easily than others. Genetic factors have
also been proposed as the cause of lowered basal metabolic rate and increased appetite. However, even those who are genetically predisposed to obesity
only become so if the environmental contributory factors are present.
Psychological factors
Low self-esteem and depression are often compensated for by food. This type of 'comfort eating' often involves high-fat snack foods and can become a major
contributing factor in the development of obesity.
Medical factors
Obesity can also be a side effect of certain disorders and conditions, including:
- Cushing’s syndrome, a disorder involving the excessive release of the hormone cortisol, which promotes fat storage
- Hypothyroidism, a condition caused by an under-active thyroid gland, which results in a decreased metabolic rate
- Neurological disturbances, such as damage to the hypothalamus, a structure located deep within the brain that helps regulate appetite
- Consumption of certain drugs, such as steroids (prednisone, cortisone) or antidepressants can lead to weight gain
Remember that most Australians who are obese are so because their lifestyle includes too little exercise and they consume excess energy for their needs.
If you are obese or simply feel you could lose a few kilos (check out our BMI calculator to find out your ideal weight for your height), then the good news
is that you can do something about it.
See your GP soon to discuss safe, reliable ways of losing weight. Be sure to seek assistance if you feel you need it - choose a well-established weight loss
program that you feel comfotable with. Remember that losing weight may not be the easiest thing you've ever done, but it will be the most worthwhile.