As you struggle to lose those last few kilos, it's worth keeping in mind that this is one of the few times in history where a thin body weight is perceived to be desirable. The only other times were in Ancient Egypt and in the early1920s. At other periods in history, the accepted and indeed desirable body shape was far heavier than what we accept today according to Professor Ian Caterson, Boden Professor of Nutrition, University of Sydney, Australia and Chairman of the Asia-Oceania Association for the Study of Obesity. Professor Caterson was speaking at the 3rd Scientific Meeting on Obesity organised by the Malaysian Society for the Study of Obesity in Kuala Lumpur in June. "Obesity has a significant impact on both the health of a nation and its health bill," said Prof Caterson. "Obesity increases the risk of heart disease, diabetes, gallstones, fatty liver, back problems and osteoarthritis. In addition, being obese increases your risk of cancer and infertility."

And the implications of obesity for a nation's health bill are staggering. In Australia, the national cost of obesity in 1997 was Aust. $464 million ($US 290 million), excluding the costs of treating heart disease, a large portion of which is also related to obesity. In the United Kingdom, approximately 145 million pounds (US$232 million) is spent annually on treating over-weight and obesity related conditions, while in the United States, obesity cost the nation US$ 5 1.6 billion dollars last year.

But just how do we define obesity? Most countries use the standards generated by the World Health Organization of the United Nations. Overweight is defined by a body mass index (BMI) greater than 25, while obesity relates to a BMI of 30 or above. The BMI is calculated by dividing body weight (in kilograms) by height (in metres) squared. For example, a man who is 1.7 metres tall and weighs 65 kilograms, would have a BMI of 22.5.

The BMI is useful for determining the level of overweight and obesity in a country and for allowing inter-country comparisons. The BMI is also used to determine a person's health risk. For someone with a BMI over 27, the risk of obesity-related diseases such as diabetes, heart disease and high blood pressure, increases significantly.

In contrast to most Western countries, populations in Asia have experienced relatively low levels of obesity. This situation, however, is starting to change and recent studies suggest that the health implications of current levels of overweight and obesity in Asian populations may have been underestimated. This is because in Asian populations, increases in health risks seem to occur at much lower BMIs. Some researchers in the region are now questioning the use of Western standards for Asian populations.

"In most Asian populations, we see diabetes occurring in people with BMIs as low as 23," said Prof Caterson. "In Japan, the risk of someone having high blood pressure increases by a factor of three if their BMI is above 24.9, a figure that confers no increased risk in Caucasian populations."

"It may be that we need to identify a different BMI at which health risk is raised and then target those groups of the population that are at risk," said Prof Caterson. It is unclear just why Asian populations have an increased risk of diseases at lower body mass indices. According to Prof Caterson, it may be related to a higher level of body fat for any given BMI, frame size or a genetic predisposition to store fat. Another theory is that nutrient restrictions to the foetus during pregnancy may "blueprint" a certain disease risk or that high-protein, high-fat feeding programmes early in life may impact on body weight later in life.

"The major factors contributing to an increase in obesity in Asia include increased affluence leading to greater food availability and reduced physical activity," said Prof Ismail Noor, President of the Malaysian Society for the Study of Obesity. Cultural factors are also important. "Asian cultures tend to use food as a reward and this can have important implications for attitudes towards food and eating," said Prof Caterson.