Background and Objectives: Shorter sleep is associated with higher weight in children, but little is known about the mechanisms. The aim of this study was to test the hypothesis that shorter sleep was associated with higher energy intake in early childhood.
Methods: Participants were 1303 families from the Gemini twin birth cohort. Sleep duration was measured using the Brief Infant Sleep Questionnaire when the children were 16 months old. Total energy intake (kcal per day) and grams per day of fat, carbohydrate and protein were derived from 3-day diet diaries completed by parents when children were 21 months old.
Results: Shorter nighttime sleep was associated with higher total energy intake (P for linear trend=0.005).Children sleeping <10 h consumed around 50 kcal per day more than those sleeping 11–<12 h a night (the optimal sleep duration for children of this age). Differences in energy intake were maintained after adjustment for confounders. As a percentage of total energy intake, there were no significant differences in macronutrient intake by sleep duration. The association between sleep and weight was not significant at this age (P=0.13).
Conclusions: This study provides the first evidence that shorter nighttime sleep duration has a linear association with higher energy intake early in life. That the effect is observed before emergence of associations between sleep and weight indicates that differences in energy intake may be a mechanism through which sleep influences weight gain.
Alex’s Notes: There are many studies examining how sleep duration and quality affect food intake and its physiological regulators in adults. Just two weeks ago we learned that sleep restriction increases caloric intake from junk food, and Carl has done numerous interviews about how inadequate sleep is linked to early death and how sleep enhances performance. Not surprisingly, we also have previously learned that vigorous physical activity enhances sleep and reduces stress above what can be achieved with moderate-intensity exercise.
Regardless of the above, few studies have examined this relationship between sleep and health in children. In one exception involving 8274 Japanese 6 to 7 year olds, those who slept less than eight hours per night were almost three times more likely to be overweight than those who slept for greater than ten hours per night, and sleep duration significantly influenced weight gain from 3 to 6 years. To expand on this relationship, the current study aimed to see how sleep interacted with energy intake in VERY young children.
This study analyzed data from 1303 families with twins in the UK, and identified five groups of sleep duration with dietary intake recorded by the parents of the children for three days (including one weekend day). Yes, I know that food logs are infamous for inaccuracies, but the children were an average of 20 months old; how much variety do you think their diet has?
Night-time sleep duration did not affect daytime napping, but
“Total energy intake was significantly higher in shorter-sleeping groups, with a linear association across sleep durations (P=0.005), with children who slept <10 h a night consuming an average of 105 kcal per day (95% CI: 17–193 kcal per day) more than those sleeping for >13 h a night.”
The increased calories were from carbohydrates and fats, not protein, and this statistical significance remained after adjustment for confounding variables. Given that no association between sleep and weight was noted, it is unlikely that bigger children simply ate more.
Now, both too much and not enough sleep can be detrimental, at least in adults. Given this, the “optimal” sleep time for these toddlers was deemed to be 11-12 hours per night. Thus, compared to this optimal amount, sleeping for less than ten hours resulted in a 50 kcal increase in daily energy intake, which may not seem like much, but is the equivalent of about 5% the total caloric intake of the subjects.
So while it is not possible to tell whether the increased energy intake was a physiological effect of shorter sleep or the result of shorter-sleeping children being awake longer and having more time to eat, we can be sure that sleeping less in childhood leads to greater energy intake in the form of carbohydrates and fats. One interesting perspective is that a longer duration of wakefulness carries a metabolic cost that initiates a series of bio-behavioral changes designed to encourage energy intake and conservation. This wouldn’t be surprising given how plastic our body is during this critical time of development.