Studies have claimed major health benefits for standing for much of the day as opposed to sitting. The difference is marked, explains Michael Mosley.

Guess how many hours a day you spend sitting? Fewer than eight? More than 10? A recent survey found that many of us spend up to 12 hours a day sitting on our bottoms looking at computers or watching television. If you throw in the seven hours we spend sleeping then that adds up to a remarkable 19 hours a day being sedentary.

Sitting down as much as this is clearly bad for us and some studies suggest that those who sit all day live around two years less than those who are more active. Most of us are guilty of excess sitting. We sit at work, in the car and at home, moving only to shift from one seat to another.

Even if you exercise on a regular basis that may not be enough. There is mounting evidence that exercise will not undo the damage done by prolonged sitting. Our technology has made us the most sedentary humans in history.

So why is sitting so damaging? One thing it does is change the way our bodies deal with sugar. When you eat, your body breaks down the food into glucose, which is then transported in the blood to other cells.

Glucose is an essential fuel but persistently high levels increase your risk of diabetes and heart disease. Your pancreas produces the hormone insulin to help get your glucose levels back down to normal, but how efficiently your body does that is affected by how physically active you are.

We wanted to see what would happen if we took a group of people who normally spend their day sitting in an office and ask them to spend a few hours a day on their feet instead.

Standing while you are working may seem rather odd, but it is a practice with a long tradition. Winston Churchill wrote while working at a special standing desk, as did Ernest Hemingway and Benjamin Franklin.

So with Dr. John Buckley and a team of researchers from the University of Chester we conducted a simple experiment. We asked 10 people who work at an estate agents to stand for at least three hours a day for a week.

Our lucky volunteers had mixed feelings about how they would get on.

"It'll be different, but looking forward to it, yes…"

"I think my feet might hurt - I'll have to wear sensible shoes…"

"The small of my back, it's going to hurt…"

"I'm worried that I'm not going to be able to stand up for all that time…[Laughs nervously]"

We asked all the volunteers to wear an accelerometer - a movement monitor - to record just how much moving about they were doing. They also wore heart rate monitors and had glucose monitors that measured their blood sugar levels constantly, day and night.

The evidence that standing up is good for you goes back to at least the 1950s when a study was done comparing bus conductors (who stand) with bus drivers (who don't). This study, published in the Lancet, showed that the bus conductors had around half the risk of developing heart disease of the bus drivers.

Since then prolonged sitting has not only been linked to problems with blood glucose control, but also a sharp reduction in the activity of an enzyme called lipoprotein lipase, which breaks down blood fats and makes them available as a fuel to the muscles. This reduction in enzyme activity leads to raised levels of triglycerides and fats in the blood, increasing the risk of heart disease.

We had good reason to believe that standing would make a difference to our volunteers, but we were also a little anxious as to how they would get on. This was the first time an experiment like this had been conducted in the UK. Would our volunteers stick to it?

They did. One woman with arthritis even found that standing actually improved her symptoms.

The Chester researchers took measurements on days when the volunteers stood, and when they sat around. When they looked at the data there were some striking differences. As we had hoped, blood glucose levels fell back to normal levels after a meal far more quickly on the days when the volunteers stood than when they sat.

There was also evidence, from the heart rate monitors that they were wearing, that by standing they were burning more calories.

"If we look at the heart rates," John Buckley explains, "we can see they are quite a lot higher actually - on average around 10 beats per minute higher and that makes a difference of about 0.7 of a calorie per minute."

Now that doesn't sound like much, but it adds up to about 50 calories an hour. If you stand for three hours a day for five days that's around 750 calories burnt. Over the course of a year it would add up to about 30,000 extra calories, or around 8lb of fat.

"If you want to put that into activity levels," Dr Buckley says, "then that would be the equivalent of running about 10 marathons a year. Just by standing up three or four hours in your day at work."

Dr Buckley thinks that although going out and doing exercise offers many proven benefits, our bodies also need the constant, almost imperceptible increase in muscle activity that standing provides. Simple movement helps us to keep our all-important blood sugar under control.

We can't all stand up at work but the researchers believe that even small adjustments, like standing while talking on the phone, going over to talk to a colleague rather than sending an email, or simply taking the stairs, will help.