Sleep deprivation also led to increased blood levels of ghrelin – a hormone that increases hunger – the following morning.
However, there was no correlation between individual ghrelin levels and food purchasing, suggesting that other mechanisms – such as impulsive decision making – may be more responsible for the increased purchasing.
The study was devised by researchers who were curious as to whether sleep deprivation might impair or alter an individual’s food purchasing choices based on its established tendency to impair higher-level thinking and to increase hunger.
“We hypothesised that sleep deprivation's impact on hunger and decision making would make for the ‘perfect storm’ with regard to shopping and food purchasing – leaving individuals hungrier and less capable of employing self-control and higher-level decision-making processes to avoid making impulsive, calorie-driven purchases,” said author Colin Chapman.
On the morning after one night of total sleep deprivation, as well as after one night of sleep, Chapman and his colleagues gave 14 normal- weight men a budget (around £40).
The participants were instructed to purchase as much as they could out of a possible 40 items, which included 20 high-calorie foods and 20 low-calorie foods.
Before the task, the men were given a standardised breakfast to minimise the effect of hunger.
‘Significantly more calories’
Sleep-deprived men purchased significantly more calories (+9%) and grammes (+18%) of food than they did after one night’s sleep. The researchers also measured blood levels of ghrelin, finding that the hormone’s concentrations were higher after total sleep deprivation. However, this increase did not correlate with food buying.
“Our finding provides a strong rationale for suggesting that patients with concerns regarding caloric intake and weight gain maintain a healthy, normal sleep schedule,” said Chapman.
Follow-up studies are needed to address whether these sleep deprivation-induced changes in food purchasing behaviour also exist under partial sleep deprivation. Additional research should also investigate sleep deprivation's potential impact on purchasing behaviour in general, as it may lead to impaired or impulsive purchasing in a variety of other contexts, said the authors.