Accumulating evidence suggests that getting less than the recommended minimum 7 hours sleep each night may be a risk factor for metabolic diseases, such as diabetes.
There is also evidence to suggest that getting too little sleep, or poor sleep, may be linked to weight gain. However, the observational nature of these studies makes it hard to gauge whether a lack of sleep causes obesity or the other way around.
A research team led by King's College London carried out a 4-week trial with 42 poor sleepers aged 18 to 64 who usually got between 5 and 7 hours of sleep a night. All the participants were either normal weight or overweight but not obese.
Half of the group underwent a 'sleep hygiene' programme that involved a 45-minute appointment with a consultant with the aim of extending their sleep by between 1 and 1.5 hours a night. This involved avoiding alcohol before bed, avoiding caffeine before bed, maintaining a regular sleep-wake routine, and not watching the clock at night.
Participants kept sleep and food diaries and wore wrist motion sensors to detect how long they slept for.
Volunteers in the other group continued with their pattern of getting insufficient sleep.
The study found that 86% of participants in the sleep extension group increased the amount of time they spent in bed. Half of them also increased sleep duration – ranging from 52 minutes to almost 90 minutes. Three of the participants achieved a weekly average of more than 7 hours sleep a night.
There was some evidence that sleep quality deteriorated in the sleep extension group, which the researchers attribute to a change of routine.
Less sugar, fat and carbs
They found that extending sleep resulted in a 9.6g reduction in the reported intake of free sugars compared to those in the other group. This equates to approximately one third of the UK dietary guidelines' daily allowance.
Free sugars are sugars that are added to foods by manufacturers or in cooking at home, as well as sugars in honey, syrups, and fruit juice.
Sleep extension is a feasible lifestyle intervention in free-living adults who are habitually short sleepers: a potential strategy for decreasing intake of free sugars? A randomized controlled pilot study, Khatib H et al, American Journal of Clinical Nutrition
King's College London
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