Spending half of your eight-hour working shift standing can require up to 13 percent more energy compared to working while being seated all the time.
Baker IDI Heart and Diabetes Institute Professor David Dunstan led the study, measuring the energy expenditure of 20 desk-based workers over two weeks while standing and sitting in a work environment.
During an average five-day working week, the extra energy used standing for four hours a day equated to a 45-minute brisk walk, Prof Dunstan said.
"If people change their workplace environment and they were also meeting their regular exercise goals, it would have a positive effect on their health," he said.
Prof Dunstan said much of the extra energy use came from the contraction of muscles used to keep the body upright.
Recent research found people who spend most of their days sitting - at work, on the bus or train and while watching TV - may not ward off heart disease, even if they exercise for 30 minutes a day as recommended.
Workers who don't have height-adjustable workstations should take a break, stand up and move every 20-30 minutes.