Researchers have found that lack of sleep raises the risk of metabolic syndrome -- a set of symptoms including high cholesterol, high blood pressure, a large waist measurement and problems controlling blood sugar.

This metabolic syndrome is actually an early warning of diabetes and heart disease, and can be counteracted with a healthier lifestyle and drugs, according to the researchers.

In the first study, a team at University of Pittsburgh School of Medicine found that sleep duration affects symptoms associated with heart disease -- in fact, it has an impact on the balance of hormones that control appetite and the feeling of fullness after a meal.

They came to the conclusion after investigating the sleep patterns of 1,214 adults between 30-54 years of age. The team found that 29 per cent of people who slept less than six hours a night met the criteria for metabolic syndrome, compared to 24 per cent for those who slept between six and seven hours a night.

The risk was lowest in people who had seven to eight hours sleep a night.

"This relationship was strongest in the group of men and women who slept less than six hours per night. On average, the odds of having the metabolic syndrome were nearly doubled in men and women who slept less than six hours, compared to those who slept between seven and eight hours per night," lead researcher Martica Hall was quoted by The Daily Telegraph.

The second research was carried out by a team at Warwick Medical School in Coventry, which reviewed 39 studies on the link between obesity and lack of sleep in a total of 30,000 children and 600,000 adults.

In children, seven of the 11 studies showed a consistent association between lack of sleep and obesity while all the studies on adults showed a link.

According to Francesco Cappuccio, who led the Warwick team, "There is a striking consistent overall association, in both obese children and adults had a significantly increased risk of being short sleepers compared to normal individuals.