No matter how much sleep you get over the weekend, it seems like you always wake up for work on Monday morning feeling tired as ever. Well, there’s actually an explanation for it.

According to Dr Paul Kelley of Oxford University, forcing staff to get up early and start work before 10am is making employees ill.

He believes our natural body clocks are completely out of sync with normal nine-to-five workings hours, posing a serious threat to performance mood and mental health.

Experiments studying circadian rhythms have shown that the average 10-year old will not fully focus on academic work before 8:30am. Similarly 16-year-old should start at 10am for best results and University students should start at 11am.

Once a former head teacher, Dr Kelley changed his schools’ start time to 10am and saw an increase in grades, by 19 per cent. He believes that companies should to the same with their employees.

“Staff should start at 10am,” he told the British Science Festival in Bradford.

“We’ve got a sleep-deprived society. It is hugely damaging on the body’s systems because you are affecting physical emotional and performance systems in the body.”

“Your liver and your heart have different patterns and you’re asking them to shift two or three hours. This is an international issue. Everybody is suffering and they don’t have to.”

Studies indicate that most people between the ages of 10-55 are missing out on 2-3 hours of sleep each day because natural sleep patterns are misaligned with the standard 9am start.

Sleep deprivation has been show to have significant effects on health. Lack of sleep has been found to affect performance, attention and long-term memory and to encourage drug and alcohol use.

It also leads to anxiety, frustration, anger, impulsive behaviour, weight gain, high blood pressure, lower immunity, stress and mental health conditions.

Dr Kelley says there is a need for a huge societal change to move work and school starting time to fit with the natural body clock of humans.