A new study claims extremes in sleep duration are related to increases in abdominal fat in young adults.

The research published in the March 1 issue of the journal SLEEP shows that African-American and Hispanic young adults with short or long sleep durations had greater increases in belly fat over a five-year period compared with those who reported sleeping six to seven hours a night.

Results show that in participants younger than 40 years of age, both short and long sleep durations were associated with significant increases in body mass index (BMI), as well as in subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) fat accumulation. Compared with people who reported a nightly sleep duration of six to seven hours, those with a self-reported sleep duration of five hours or less per night had an average BMI increase over a five-year period that was 1.8 kg/m2 higher, and greater accumulations of SAT (42 cm2) and VAT (13 cm2); and those who reported sleeping eight hours or more had a BMI increase that was 0.8 kg/m2 higher, as well as greater accumulations of SAT (20cm2) and VAT (6 cm2). No significant relationship existed between sleep duration and abdominal fat change in participants older than 40 years of age.