The dieter's dream of losing weight without the need for hard exercise may have come true as a new study has found that exercising for less than three minutes can burn off 200 calories.

Researchers at the Colorado State University and the University of Colorado Anschultz Medical Campus found that a 150-second burst of exercise can use up the rough calorie equivalent of four fingers of Kit Kat choclate or a large glass of wine.

The calories are burnt only if the exerciser does sprint interval training, which involves short bursts of energy between long periods of recovery, said the research team.

They compared energy expenditure of study participants on two different days. On one day the participants undertook sedentary activities such as watching TV or using a computer. On the other day they took part in a sprint interval workout.

The workout involved pedalling as fast as possible on a stationary bike for five 30-second intervals, separated by four-minute periods of slow pedalling.

Findings showed that on the sprint interval day, participants burnt, on average, an extra 200 calories from doing just 2.5 minutes of intense exercise.

Study leader Kyle Sevits said: "Research shows that many people start an exercise programme but just can't keep it up.

"The biggest factor people quote is that they don't have the time to fit in exercise. We hope if exercise can be fit into a smaller period of time, then they may give exercise a go and stick with it.

"Burning an extra 200 calories from these exercises a couple of times a week can help keep away that pound or two."

According to government guidelines, people aged between 19 and 64 should spend at least two-and-a-half hours a week doing moderate exercise in bouts of 10 minutes or more. Alternatively, they can do 75 minutes of vigorous exercise over a week.