Time poor and overworked Generation Yers are exercising less and becoming overweight earlier than their Baby Boomer parents were at the same age, a study by the University of Sydney has shown.

Using studies from the last four National Health Surveys between 1990 to 2005, researchers looked at the effects of generation and age on the duration and kilojoules expended in leisure time physical activity over the period.

Associate Professor in Clinical Nutrition and Dietetics Margaret Allman-Farinelli, from the School of Molecular and Microbial Biosciences at the University of Sydney, said the results showed Generation Y, was turning into 'Generation Y bother'.

“The results indicate that younger Australians are living increasingly more sedentary lifestyles than their predecessors, with less time spent in physical exercise than people of retirement age,” Allamn-Farinelli said.

The study, published in the British Journal of Nutrition, showed that Generation Y males are exercising far less than previous generations were at the same age, largely due to working longer hours.

The results also revealed that women in their twenties are doing the least amount of exercise, spending only a little over fifteen minutes per day in leisure time physical activity.

Health authorities recommend at least 30 minutes of physical activity on most days to maintain a healthy weight, with double that time needed to combat overweight and obesity.

Despite the decline in physical activity in younger generations, the study revealed a peak in the number of older Australians engaged in physical activities, with the majority of retirees reaching the recommended 30 minutes of exercise per day.

"These people are less time-poor and can actually concentrate on their health," Allman-Farinelli said.

The findings justify the rising obesity and overweight figures amongst younger Australians, of whom nearly 38 per cent aged 18-24 are overweight.

The complications that arise from obesity, such as cardiovascular disease, diabetes and cancer, cost Australia an estimated $58 billion per year.