An international team has found that working at night and sleeping during the day affect the body's natural rhythms and slows down the rate it burns energy resulting in increased risks from obesity, diabetes and even heart disease.

"In the long run, the physiological impact of shift work on several markers involved in the regulation of body weight – leptin, insulin, cortisol – seems to contribute to the increased risk for development of diabetes, cardiovascular disease and obesity," said lead author Frank Scheer.

For their study, researchers, led by Harvard Medical School, took 10 volunteers and subjected them in a laboratory to the equivalent of working various shift patterns during a ten-day period.

The volunteers, which included five women and slept and ate across all hours of the day and night, were monitored for alterations in heart rate and body temperature which all suggested a slowing of the metabolic rate.

They also showed changes to levels in certain hormones important to feelings of stress and well being. The disrupted patterns caused three patients with no history of diabetes to show signs similar to people susceptible to developing it.