Chubby Owls and Skinny Larks?

One of the recurring topics at the Obesity Summit was the importance of sleep in terms of its effects on ingestive behaviour, metabolism and other important parameters.

Now a study by Kelly Baron and colleagues from Northwestern University, Chicago, published in OBESITY, adds an additional dimension to this discussion, i.e. the importance of sleep timing.

As regular readers may recall, I have previously posted the results of animal studies demonstrating the impact of timing of feeding in energy homeostasis – feeding mice during the day (their night) leads to more weight gain than feeding them the same amount of calories during the night (their day).

In their study, Baron and colleagues now evaluated the role of sleep timing in dietary patterns and BMI in 52 (25 females) volunteers who completed 7 days of wrist actigraphy and food logs.

Participants were classified as having normal sleep times if midpoint of sleep was between 1:00 am to 5:29 am, and participants were classified as having late sleep times if midpoint of sleep was 5:30 am or later, which is past the 50th percentile of sleep times in the population (4:00 am)

Late sleepers also consumed more calories at dinner and after 8:00 PM, had higher fast food, full-calorie soda and lower fruit and vegetable consumption.

Not surprisingly, therefore, higher BMI was associated with shorter sleep duration, later sleep timing, caloric consumption after 8:00 PM, and fast food meals.

In addition, calories consumed after 8:00 PM predicted BMI after controlling for sleep timing and duration, suggesting that eating after 8:00 PM may increase the risk of obesity, independent of sleep timing and duration.

If these associations are indeed causally related (which will need to be demonstrated in intervention trials), two important clinical recommendations could emerge:

Get at least half your night’s sleep before 5.30 am and get your day’s supply of calories before 8.00 pm.

Wonder if anyone has experienced changes in their eating behaviour and/or weight with changes in sleep timing or not eating after 8.00 pm.

As for me, I probably just need to figure out which time zone actually counts for me – after all, it is always before 8.00 pm somewhere.

Edmonton, Alberta

Baron KG, Reid KJ, Kern AS, & Zee PC (2011). Role of Sleep Timing in Caloric Intake and BMI. Obesity (Silver Spring, Md.) PMID: 21527892