Sydneysiders have the lowest levels of physical activity among residents in Australia's capital cities, with a lack of recreational facilities partly blamed for keeping people on the couch.
But the full range of factors that led some people to exercise more than others was not well understood, Adrian Bauman from Sydney University's school of public health said.
Professor Bauman led a review of more than 1000 papers on physical activity in a paper published in international medical journal The Lancet today.
Most existing studies have been conducted in a few affluent countries, Professor Bauman said.
"Inactivity is a much greater health threat than obesity, yet many existing studies tend to be focused on higher income countries, look at small groups of people that don't represent the broader population and consider only a few factors that lead to physical activity," he said.
"Future studies need to include larger populations and examine not just age, sex, and motivation to exercise, but also factors outside of the health sector such as urban planning, transportation systems, local policies and social environment."
Such studies were vital to prevent diseases related to inactivity including cardiovascular disease, diabetes, obesity, colon cancer, high blood pressure and osteoporosis, he said.
A number of studies found lighting and aesthetics, such as in parks and ovals, could boost activity levels by as much as 50 per cent and that access to ovals, bike lanes and bike storage facilities were also important – reasons that Perth and Canberra were the nation's most active cities, Professor Bauman said.
Those who were male, young, wealthy and had family and social support were among the most likely to exercise, the review found, while Professor Bauman said the elderly and some migrant groups were among the least active.
"Interestingly, we found poorer people were much more likely to walk to public transport or the entire way to work, and were more active once there, while affluent groups are doing more physical activity in their leisure time but spent more time sitting down throughout the day."
The review pointed to new evidence suggesting some people were genetically predisposed to being physically active, while evolutionary factors and obesity might account for inactivity, but Professor Bauman said such factors only accounted for about 5 per cent of predisposition to exercise.
"Not enough to be used as an excuse," he said.
His review is part of a series on physical activity in The Lancet.
The series include a paper from Boston University that found a lack of physical activity was responsible for about 5.3 million of the 57 million deaths globally in 2008 and that the burden of physical inactivity and shortening of life expectancy was similar to that caused by tobacco smoking.
"We're not suggesting lycra – we're just suggesting going for a 30-minute walk every day," he said.