Research finds more young men are obese than previously thought

31 July 2014

Deakin University research has revealed that more young Australian men are likely to be obese than previously estimated.

Deakin University research has revealed that more young Australian men are likely to be obese than previously estimated.

The study by researchers with Deakin's IMPACT Strategic Research Centre found that 24 per cent of young Australian men are obese, as opposed to the previous estimate of eight per cent. They believe the discrepancy is due to inaccuracies with the Body Mass Index (BMI) measurement system.

"While we found BMI-based estimates for obesity in most women were fairly accurate, the use of the BMI markedly underestimated the amount of body fat in young men aged 20-29," explained Professor Julie Pasco, deputy director of the IMPACT Strategic Research Centre and Head of the Epi-Centre for Healthy Ageing.

"The fat to weight ratio appears to be disproportionately high in this group, which means many young men are carrying more fat, proportional to their weight, than expected."

The study analysed data from around 2500 randomly-selected men and women, aged 20–96 years, who are all participants in the long-term Geelong Osteoporosis Study. Whole-body scans were used to more accurately measure fat and reveal actual obesity levels.

Professor Pasco said extra fat young men were carrying was having an effect similar to premature aging.

"It means that an alarming number of young men are exhibiting the physical characteristics of older men, where muscle mass has been replaced by fat. This has particular implications for muscle weakness and potential osteoporosis later in life," she said.

"It seems that the modern sedentary lifestyle and poor diet of this group have contributed to this new trend at a population level.

"Global and Australian estimates of obesity have been based on Body Mass Index. Yet, as a measure of body weight for height, this technique doesn't account for different body types. It doesn't distinguish between fat, muscle or bone, which contribute to body weight differently for men and women, and for different age groups."

Obesity has nearly doubled, globally, over the past three decades, with women bearing the brunt of the trend. Approximately one in three women and one in five men are obese - and an estimated two thirds of the adult population are either overweight or obese.

"Using BMI has been simple to measure and easy to calculate, so it has become an entrenched means of gauging whether people are over-weight or obese. However, we have discovered that it is not accurate, especially in the case of both young and elderly men," Professor Pasco said.

"We knew that the BMI overestimates obesity in muscular body builds and underestimates obesity in the elderly, but the underestimation of obesity in young men is a new finding."

Professor Pasco and her colleagues say that, as a result of the findings, instead of using one "cut off" threshold for defining obesity, different sex and age-specific BMI "cut off" values should be used by health professionals, to achieve more accurate estimates for the different groups. This would improve risk assessment for disease, morbidity and mortality, and help in population health management.

"We have an obesity epidemic on our hands. We need the most accurate information possible so that we can address this issue and encourage people to improve their diet and lifestyle," Professor Pasco said.

The results of the study were recently published in the open access journal BMC Obesity

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