Evening eating, BMI, and waist-to-height ratio among preschoolers

Chrononutrition, a broad concept examining the aspect of time in eating, has gained attention in research relating to overweight and obesity. Eating that happens later in the day is one aspect of chrononutrition that has been associated with overweight/obesity in some studies. Furthermore, it has been suggested that these associations may differ depending on chronotype, which describes individual differences in circadian rhythms. Late eating might be differently associated with weight status in people with earlier chronotypes compared to later chronotypes. Thus far, this research has focused mainly on adults. Therefore, we wanted to examine 1) associations of timing of eating in the evening with body mass index z-score (BMI z-score) and waist-to-height ratio (WHtR) among preschool-aged children, and 2) whether the associations differ depending on the child’s chronotype.

We used data from 672 children who were 3–6 years old (DAGIS survey 2015–2016). BMI z-score, and WHtR were calculated from weight, height and waist circumference measured from the children. BMI z-score describes BMI in children and WHtR is used as a measure of abdominal obesity. Timing of eating in the evening was examined with three variables: 1) clock time of the last eating occasion (last time the child ate that day), 2) time between the last eating occasion and sleep onset, and 3) percentage of total daily energy intake consumed within two hours before sleep onset. These variables were formed using food record data reported by parents and sleep data from accelerometers the children wore. Midpoint of sleep (a clock time) on the weekend was used as a measure of chronotype.

We found that eating closer to sleep onset (variable 2) and consuming larger proportion of the day’s energy intake close to sleep onset (variable 3) were associated with higher waist-to-height ratio. Chronotype did not influence any of the studied associations. These results suggest that the association between later eating and overweight/obesity seen in some previous studies may be present already in young children. Moreover, because the clock time of the last eating occasion had no associations, how close to one’s bedtime one eats might be more relevant than at what clock time one eats. This might relate to the role of individual circadian rhythms since sleep timing is one marker of circadian rhythms. However, more research is needed to draw stronger conclusions.

Association of the timing of evening eating with BMI Z-score and waist-to-height ratio among preschool-aged children in Finland
Rahkola J, Lehtimäki A-V, Abdollahi AM, Merikanto I, Vepsäläinen H, Björkqvist J, Roos E, Erkkola M, Lehto R. British Journal of Nutrition.