There is an association between sleep duration and body weight. However, the cause and effect are not fully understood and confounding variables could be present. For example, stress is known to disrupt energy balance and also disrupt sleep and so the possibility arises that it is stress that drives weight gain through sleep deprivation. This is interesting because populations in Western nations are exposed to ever higher amounts of mental stress, and at the same time grow ever fatter. However, the association between sleep and body weight is made more complex because it is the sleep quality, particularly the amount of slow wave sleep, that may drive bodyweight changes rather than actual sleep duration. In addition, the very different requirements for sleep between individuals make correlations difficult to interpret. That being said, it has been reported that changes to energy metabolism do occur with reductions in the normal duration of sleep, and these changes to metabolisms are consistent with the ability to cause weight gain and obesity.
For example, in one recent study1, researchers investigated the association between disrupted sleep patterns and energy metabolism in health subjects. Fifteen healthy men, were randomly assigned in a crossover fashion (all subjects received both treatments in a random order) to either a normal undisturbed nights sleep, or to a night of sleep disturbance that reduced their normal sleep quality. Analysis of the results showed that during undisturbed sleep, both sleep quality and the restorative slow wave sleep were associated with total energy expenditure, activity-induced energy expenditure. When sleep was disturbed, the amount of slow wave sleep, REM sleep and total sleep time reduced and this caused reductions in total energy expenditure and activity-induced energy expenditure. The reductions in sleep quality were associated with a higher energy energy intake and a disruption to normal energy balance. Generally undisturbed sleep produced higher oxidation rates for carbohydrates, and disturbed sleep shifted substrate utilisation towards fat oxidation.
Therefore it can be shown that changes to the quality of sleep cause changes to the normal energy metabolism pathways and this may in some way explain body weight changes seen in those who chronically have too little sleep. This study is interesting because those who normally had the highest sleep quality were adversely affected more by sleep disruption. Both REM sleep and slow wave sleep seem to be the most restorative stages of sleep and it is disturbances to these stages that are likely have the greatest effects on the degree of sleep quality. Previous studies have suggested that fragmentary sleep characterised by low amounts of REM and slow wave sleep are one of the possible causes of obesity, and the results of this study support that contention. The shift in energy substrate utilisation is interesting because it suggests a hormonal shift in those exposed to fragmentary and disturbed sleep patterns. This suggests that dietary changes in those exposed to sleep deprivation may offset some of the detrimental effects.
Dr Robert Barrington’s Nutritional Advice: Sleep is a very important aspect of human health. Recommendations as to the amount of sleep are pointless as everyone requires different amounts. However, it is important to maintain high quality undisturbed sleep. As a guide, you should wake refreshed and rejuvenated.
RdB
