Children who are allowed to stay up late at weekends are more likely to be obese, according to a study published today.
Those who are told to go to bed early on weekend nights get a chance to catch up on the sleep they do not get throughout the week, and tend to be thinner, found the report published in the American journal Pediatrics.
Academics monitored 308 children from four to 10 years old, measuring the body mass index (BMI) of each and examining their sleep patterns using wrist movement sensors.
The children averaged eight hours per night throughout the week - less than is recommended - with no significant differences between the fatter and thinner children.
However, at weekends the obese children had shorter and more irregular sleep patterns, found researchers at Chicago University.
Those with poorer weekend sleep patters had worse health in terms of higher insulin levels - that can lead to Type II diabetes over a prolonged period - higher levels of 'bad' (LDL) cholesterol, and higher levels of C-reactive protein, that has been linked with heart disease in later life.
The authors found: "Obese children were less likely to experience “catchup” sleep on weekends and the combination of shorter sleep duration and more-variable sleep patterns was associated with adverse metabolic outcomes."
Lack of sleep is believed to lead to increased production of ghrelin, a hormone produced in the stomach, and the reduced release of a hormone called leptin in fat cells.
Too much ghrelin and too little leptin have been shown to result in a larger appetite.
The authors concluded: "Public health campaigns aiming to educate families regarding the benefits of longer and more-regular sleep may lead to decreased obesity and metabolic dysfunction trends for our children."
The American Academy of Sleep Medicine recommends that pre-school children get between 11 and 13 hours of nightly sleep, while school-age children should get 10 to 11 hours per night.