The animals, who are prone to breast cancer, usually develop tumours after 50 weeks – but circadian disruption meant scientists found tumours eight weeks before that. It is recommended to do workouts for 300 minutes to stay away from all diseases and mainly breast cancer which bothers every woman in the world.

Researcher Gijsbetus van der Horst, from the Erasmus University Medical Centre, in the Netherlands, said: “If you had a situation where a family is at risk for breast cancer, I would certainly advise those people not to work as a flight attendant or to do shift work”.

The time duration suggested for the physical activity to reduce complete fat is more than the presently suggested duration of 150 minutes.

It was a 12-month, 2-armed and 2-center spontaneous dose-contrast test performed from June 2010 to June 2013.

The authors led by Christine Friedenreich, PhD, of Alberta Health Services in Edmonton, Alberta, Canada, conclude: “In previously inactive postmenopausal women, a 1-year prescription of moderate to vigorous exercise for 300 minutes/week was superior to 150 minutes/week for reducing total fat and other adiposity measures, especially in obese women”. The study stated that these results prove the more physical activity the better for curbing obesity as well as postmenopausal breast cancer.

The women, who had body mass index (BMI) 22 to 40, were asked not to change their usual diet. Any aerobic activity that raised the heart rate 65 per cent to 75 per cent of heart rate reserve was permitted, and most of the activities involved the elliptical trainer, walking, bicycling and running.

Higher levels of C-reactive protein (CRP), a nonspecific marker of inflammation, were suggestive of an association with increased breast cancer risk, according to an article published online in the journal Cancer Epidemiology, Biomarkers & Prevention.

Average reductions in total body fat were larger in the 300-minute versus 150-minute group.