Lack of sleep combined with free access to food increases calorie consumption, leading to fat accumulation, especially in the abdominal area.
A new discovery from a randomised controlled crossover study led by Naima Covassin, PhD, a cardiovascular medicine researcher at Mayo Clinic, found that lack of sleep led to a 9% increase in total abdominal fat area and an 11% increase in abdominal visceral fat, compared to control sleep. Visceral fat is deposited deep inside the abdomen around the internal organs.
The findings are published in the Journal of the American College of Cardiology and was funded by the National Heart, Lung and Blood Institute.
Lack of sleep and weight gain: finding the connection
Lack of sleep is a growing problem and is often a result of shift work, social media, and technology used during traditional sleep hours. But how does this lead to increased unhealthy abdominal fat? The research team designed a randomised controlled study to find answers.
The study participants were 12 healthy people who did not classify as obese, each spending two 21-day sessions in the inpatient setting. Participants were randomly assigned to the control (normal sleep) group or restricted sleep group during one session and the opposite during the next session, after a three-month washout period. Each group had access to food throughout the study. During the study, researchers monitored energy intake, energy expenditure, body weight, body composition, fat distribution and circulating appetite biomarkers.
The first four days were an acclimation period. During this time, all participants were allowed nine hours in bed to sleep. For the following two weeks, the restricted group was allowed four hours of sleep and the control group maintained nine hours. This was followed by three days and nights of recovery with nine hours in bed for both groups.
Analysing the findings of the study
Lack of sleep led to the participants consuming 300 extra calories per day, eating approximately 13% more protein and 17% more fat compared to the acclimation stage. That increase in consumption was highest in the early days of lack of sleep 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 CT scan and would otherwise have been missed, especially since the increase in weight was quite modest — only about a pound,” Dr Covassin said. “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.”
Dr Somers said 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 diabe