Lack of sufficient sleep combined with free access to food increases calorie consumption and fat accumulation – especially unhealthy fat inside the belly. These were the findings from a study from the Mayo Clinic in Rochester, Minnesota, in the United States. Not getting enough sleep led to a nine per cent increase in total abdominal fat area and an 11 per cent increase in abdominal visceral fat – the fat deposited deep inside the abdomen around internal organs that is strongly linked to cardiac and metabolic diseases. The findings were published in the Journal of the American College of Cardiology . Lack of sufficient sleep is often a behaviour choice, and this choice has become increasingly pervasive. More than one-third of adults in the US routinely do not get enough sleep , in part because of shift work, and smart devices and social networks being used during traditional sleep times. Also, people tend to eat more during longer waking hours without increasing physical activity. “Our findings show that shortened sleep – even in young, healthy and relatively lean subjects – is associated with an increase in calorie intake, a very small increase in weight, and a significant increase in fat accumulation inside the belly,” says Dr Virend Somers, a professor of cardiovascular medicine, and the study’s principal investigator. The secret to a good night’s sleep: listen to your body clock Normally, fat is deposited under the skin, Somers says, but the inadequate sleep appears to redirect fat to the more dangerous visceral compartment. “Importantly, although during recovery sleep there was a decrease in calorie intake and weight, visceral fat continued to increase. This suggests that inadequate sleep is a previously unrecognised trigger for visceral fat deposition, and that catch-up sleep, at least in the short term, does not reverse the visceral fat accumulation. “In the long term, these findings implicate inadequate sleep as a contributor to the epidemics of obesity , cardiovascular and metabolic diseases,” says Somers. Twelve healthy people who were not obese each spent two 21-day sessions taking part in the study. They were randomly assigned to the normal sleep group (the control group) or restricted sleep group during one session, and the opposite during the next session, after a three-month period in between. Each group had access to free choice of food throughout the study. Researchers monitored and measured how many calories they ate and drank ; energy expenditure; body weight; body composition; fat distribution, including visceral fat or fat inside the belly; and appetite biomarkers. For the acclimation period in the first four days, all participants were allowed nine hours in bed to sleep. For the following two weeks, the restricted sleep group was allowed four hours of sleep and the control group continued with nine hours. This was followed by three days and nights of recovery with nine hours in bed for both groups. What saves your health, money and the planet? A whole food plant-based diet The participants consumed more than 300 extra calories per day during sleep restriction, eating around 13 per cent more protein and 17 per cent more fat, compared to the acclimation stage. That increase in consumption was highest in the early days of sleep deprivation and then tapered off to starting levels during the recovery period. Energy expenditure stayed mostly the same throughout. “The visceral fat accumulation was only detected by CAT scan and would otherwise have been missed, especially since the increase in weight was quite modest – only about a pound [0.45kg],” says cardiovascular medicine researcher Naima Covassin, who led the study. “Measures of weight alone would be falsely reassuring in terms of the health consequences of inadequate sleep. Also concerning are the potential effects of repeated periods of inadequate sleep in terms of progressive and cumulative increases in visceral fat over several years.” Somers says behavioural interventions, such as increased exercise and healthy food choices, need to be considered for people who cannot easily avoid sleep disruption, such as shift workers. More study is needed to determine how these findings in healthy young people relate to people at higher risk, such as those who are already obese, or have metabolic syndrome or diabetes . Like what you read? Follow SCMP Lifestyle on Facebook , Twitter and Instagram . You can also sign up for our eNewsletter here .