Obesity is a chronic disease associated with lower life expectancy, a variety of health problems and a reduced quality of life.

No longer just a cosmetic issue brought on by a lack of self-discipline, the World Health Organisation (WHO) recognises that obesity is a chronic progressive disease. It has recently overtaken smoking as the leading cause of preventable death in Australia.

The Body Mass Index (BMI) is a practical way to evaluate the degree of being overweight. It indicates whether your weight is appropriate for your height.

  • If your BMI is between 25 and 30, you are overweight
  • If your BMI is above 30, you have obesity
  • If your BMI is 35, you have severe obesity

Research shows that behaviour is not the sole determinant of obesity, which explains why lifestyle changes, including diet and exercise, can be ineffective.

It is commonly accepted that when energy intake exceeds energy expenditure, body fat increases.

This theory, however, does not take into consideration the complex factors underlying excessive weight gain.

With the incidence of obesity rising worldwide, despite increased public awareness, it is evident that weight gain is not merely a problem of self-control or a sign of personal weakness.

Beyond Behaviour

The metabolic processes underlying weight gain have a strong inherited component. Obesity is a feature of at least 24 genetic disorders and studies in large populations have identified variants in genes that predispose someone to obesity.

Appetite is very hard to control. The biochemical pathways regulating appetite are powerful. A person’s feedback control system carries complex messages regarding the body’s nutrient state from the gastrointestinal tract to a part of the brain called the hypothalamus, which regulates appetite.

It is believed that people with obesity have a defective feedback control system – the appetite-regulation part of the brain does not function properly, and instead, continues to stimulate hunger and food-seeking behaviour, despite adequate energy reserves.

It has been shown that those prone to obesity absorb more calories from their diet. This is affected by factors such as a person’s gut flora (the micro-organisms found in the gut) and their hormone response to food.

Activity and exercise account for approximately 20 per cent of the energy a person expends. Around 70 per cent of energy is expended through metabolic processes and another 10 per cent through the processing of food.

Energy expenditure varies between people. There is a strong relationship between resting energy expenditure and fat-free mass, which makes weight loss increasingly difficult for people with higher fat reserves.

People can become overweight any time, however there are certain life events that can trigger weight gain. These include pregnancy, menopause, periods of sleep deprivation, giving up smoking, transitioning from an active adolescent to a more sedentary lifestyle, and when beginning or changing medications.

There are a number of medications that can cause weight gain including oral hypoglycemics, hormonal therapy, steroids, antidepressants, antihistamines, anti-hypertensives and anti-epileptic medications.

Why is overcoming obesity such a challenge?

Obesity is self-perpetuating. Excess fat reduces energy levels, making it more difficult to exercise. Intense or lengthier exercise causes the body to release the stress hormone cortisol, which not only contributes to hunger, but also promotes fat storage independently of calorie intake.

For men, extra belly fat also raises oestrogen levels and lowers testosterone, making it even harder to gain muscle and lose fat. Reduced muscle mass means a lower base rate of metabolism, increasing the ease of weight gain.

Few people with obesity experience long-term weight loss by lifestyle changes alone. Surgery puts people with obesity back on an even playing field and allows their efforts toward weight management to be effectual and sustainable.