Regular exercise is not only vital for maintaining a healthy weight, but it also has another positive impact -- physical activity allows people to keep burning calories even at rest, a new study has claimed.

An international team, led by Sydney University, has carried out the study and found that regular exercise switched on metabolism and energy burning cells, which, in turn, raises the body's ability to burn calories while at rest.

The study found even low levels of physical activity, such as a daily brisk walk for 30 minutes, is vital to turn on the right molecular switches so that cells can metabolise and burn energy effectively.

Lead researcher Prof Frank Seebacher said the bodies of mammals, including humans, were designed to be exercising regularly.

"Our research using a mammal model shows a sedentary lifestyle is doubly bad and may lead to weight gain because energy is not used up by muscular activity and metabolic signalling is disrupted, which reduces the body's ability to burn energy," he said.

In humans and other mammals, the metabolism of a resting body will increase as ambient temperatures decrease below 30 to 35 degrees Celsius. This means that resting bodies will burn more energy at cooler conditions, below 30 degrees Celsius. So, in theory, human bodies should be stimulated to burn energy at everyday 'cold' temperatures.

However, the results of the study, showed in tests using wild native Australian bush rats that cold conditions did stimulate a rise in metabolism -- but not in the absence of exercise.

"Rats that had exercised for half an hour a day did show a metabolic response to cold, and burnt more energy as expected. But in rats that did not exercise, lowering the air temperature even down to a chilly 12 degrees Celsius did not stimulate their metabolism and energy consumption at all," Prof Seebacher said.

According to the researchers, this study is the first of its kind to show the interaction between exercise and temperature on cellular metabolism and shows that physical activity has a subtle effect on our body's energy expenditure by opening up a number of cryptic genes that control the rate of cellular metabolism.

"To take advantage of the metabolic boost we receive at temperatures below 30 degrees Celsius, we need to do some light exercise every day. In other words, you don't need to take exercise seriously, just regularly," Prof Seebacher said.