According to scientists, intense exercise for just two and a half minutes a day could help keeps the pounds off.

A study shows that concentrated effort can burn as many as 200 extra calories, provided the spurts are broken up with longer periods of easy recovery.

It is the latest evidence to support High Intensity Training (HIT), whereby a number of short bursts of intense exercise are teamed with short recovery breaks in between.

Although HIT is not new, recent research suggests it can deliver the same physical benefits as traditional endurance training.

Researcher 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 fitted into a smaller period of time, they may give it a go.”

Official guidelines state adults should do 150 minutes of moderate, or 75 minutes of vigorous, exercise a week.

During the three-day study, five healthy men, all between the ages of 25 and 31, lived in a sealed off room so that their oxygen, carbon dioxide and water levels could be monitored to calculate how many calories they burnt.

They were also given a diet precisely tailored to meet their energy requirements. For two of the days, they spent most of their time in sedentary activities, such as using a computer.

On the last day they performed five 30-second sprint workouts at high resistance on a stationary bicycle.

Each burst was separated by a four-minute period of recovery in which the men pedaled slowly with little resistance.

The results found the volunteers burned an extra 200 calories on average over the workout day.

Although the researchers cannot prove the technique leads to weight loss, it suggests that intense, but brief, bursts of exercise could help people maintain their weight.

Kyle Sevits, of Colorado State University, which conducted the research, said burning an extra 200 calories a couple of times a week could combat average weight gain of a couple of pounds each year.

“Motivating yourself can be very hard. The way this could work in the real world is with the guidance of a personal trainer,” he added.

Experts believe HIT improves insulin sensitivity, which is important for keeping blood glucose levels stable, possibly because it uses more muscles than conventional aerobic training.

It may also help to break down stored glucose in muscles.

But scientists warn not everyone responds to this form of training because genes play a part in determining whether you gain any benefit.

“Anyone with medical conditions should seek medical advice before undertaking it,” they added.