The research team, led by Hannah Lundh of the Centre for Physical Activity in Region Västra Götaland and colleagues at the University of Gothenburg, recruited 39 children aged 6 to 12 who had been referred to outpatient paediatric clinics for obesity treatment, along with one parent each. The children, 19 of them girls, had a mean age of 9.7 years and a mean body mass index standard deviation score of 3.0, indicating severe obesity relative to Swedish reference populations. Their parents, 20 of them mothers, averaged 42.2 years of age. Fifty-seven percent of the parents were born in Sweden, 16 percent in other European countries, and 27 percent outside Europe, giving the sample a broadly diverse socioeconomic and cultural profile.

Each child-parent pair wore a small Axivity AX3 accelerometer on an elastic belt around the waist, positioned over the right hip close to the body’s centre of mass, for seven consecutive days and nights. The devices sampled movement at 50 Hz with an acceleration range of plus or minus 8 g, and participants kept diaries of bedtime, waking time, cycling, water activities and strength training to help researchers identify sleep and non-wear periods. A valid day required at least 10 hours of wear time, and a valid week required at least two such days — a deliberately lenient threshold that sensitivity analyses showed made no difference compared with the traditional four-day requirement, but which maximised the number of pairs that could be included.

The data processing was where the study distinguished itself technically. Rather than applying conventional low-pass filters that can misclassify vigorous movement as noise, the team used the 10 Hz Frequency Extended Method, which has been shown in calibration work to capture higher-intensity activity more faithfully. Data were reduced into 3-second epochs, a window short enough to register the brief, sporadic bursts that characterise children’s movement. Perhaps most notably, the researchers set the cut-point for moderate-to-vigorous physical activity at 4 metabolic equivalents rather than the traditional 3 METs, arguing that 3 METs corresponds to a slow walking pace of just 3 to 4 kilometres per hour and shows minimal association with cardiometabolic health, whereas clinically meaningful benefits begin around 4 METs, roughly a brisk walk of 4 to 5 kilometres per hour. Cut-points of 52 mg and 388 mg for children and 39 mg and 331 mg for adults marked the boundaries between light activity and moderate-to-vigorous activity.

The headline numbers were sobering. Children spent an average of 9.8 hours per day in sedentary behaviour and just 0.7 hours — about 42 minutes — in moderate-to-vigorous activity, with another 3.9 hours in light activity. Their parents sat even longer, averaging 12.3 sedentary hours daily, with only 0.3 hours of moderate-to-vigorous activity and 3.4 hours of light activity. Only six of the 39 children, or 15 percent, met the World Health Organization recommendation of at least 60 minutes of moderate-to-vigorous activity per day for ages 5 to 17. Among parents, the picture was bleaker still: just two of 38, or 5 percent, achieved the adult guideline of 150 minutes of moderate activity per week.

The central analytical question was whether children’s and parents’ behaviours tracked together within each pair. Using intraclass correlation coefficients in two-way mixed-effect models, the team found a statistically significant but weak correlation for sedentary time, with an ICC of 0.14 and a p-value of 0.017. By the conventional interpretation scheme of Koo and Li, any value below 0.5 counts as weak, so the shared sitting habit was real but modest. The correlation for light activity was stronger, at 0.24, but fell just short of significance with a p-value of 0.050. For moderate-to-vigorous activity, the correlation was weaker still, at 0.11, and clearly non-significant. Bland-Altman plots visualising the within-pair differences showed enormous variability: some pairs moved in near lockstep, while others diverged dramatically.

Interestingly, the generations differed systematically in how they spent their days. Children accumulated significantly more moderate-to-vigorous activity than their parents — a mean paired difference of roughly 27 minutes per day — while parents sat significantly more than their children. This inversion of the intuitive picture, in which adults might be expected to be the more active party, underscores how deeply sedentary adult lifestyles can become even in families actively engaged with paediatric obesity services. It also suggests that children in this clinical population, despite falling far short of guidelines, remain more physically capable of spontaneous movement than their parents.

The sedentary finding carries particular weight because it contradicts much of the existing parent-child literature. Previous systematic reviews, covering predominantly healthy, non-obese children, have generally reported weak to moderate positive associations between parent and child physical activity, and a large meta-analysis found a small effect of parental modelling on children’s activity. Only one of the 65 studies across two major reviews had examined accelerometer-measured associations in an obese paediatric population. The Swedish authors suggest several reasons their results may diverge: earlier studies often relied on self-report, which is prone to bias; many used the lower 3 METs threshold, inflating apparent activity levels; and crucially, previous cohorts tended to include younger children, aged 2 to 10, who are more dependent on their parents and more likely to share their activities. Children aged 6 to 12, by contrast, increasingly move in school and peer contexts their parents never see.

The study’s limitations are candidly acknowledged. The cross-sectional design rules out any causal inference — sitting together may reflect shared environment, modelling, genetic predisposition, or all three. The sample of 39 pairs fell short of the original target of 60, partly because of pandemic-related staffing problems, and no formal power calculation was performed, so a larger sample might have detected significant correlations that here hovered near the threshold of significance, particularly for light activity. The team did not collect parents’ body mass index, which likely influenced parental activity levels given the genetic component of obesity, nor did they record living arrangements, meaning some children may have spent the measurement week with the non-participating parent. Selection bias is also possible, since families with positive attitudes toward activity may have been more willing to enrol.

Still, the implications for treatment are concrete. The WHO recommends family-based, multi-professional interventions as first-line treatment for childhood obesity, and the Swedish physical activity on prescription model places parental involvement at its core. If sedentary time is the one behaviour where parent and child genuinely mirror each other, the authors argue, then interventions for this population might profitably begin by targeting sitting time together — a change that over time could open the door to increased activity — while recognising that role modelling through parental exercise may matter more for some families than others. Facilitating access to activity opportunities, initiating outings and offering encouragement may ultimately prove more powerful levers than a parent’s own workout routine. Larger samples, other settings and longitudinal designs, the researchers conclude, are needed to untangle whether shared sedentary habits are cause, consequence or coincidence in the trajectory of childhood obesity.

Subject of Research: Parent-child associations in accelerometer-measured physical activity and sedentary behaviour among children with obesity

Article Title: Physical activity and sedentary behaviour amongst children with obesity – exploring cross-sectional associations between child and parent

Article References: Lundh, H., Arvidsson, D., Greven, C., Fridolfsson, J., Börjesson, M., Boman, C., Lauruschkus, K., Lundqvist, S., Melin, K., & Bernhardsson, S. (2025). Physical activity and sedentary behaviour amongst children with obesity – exploring cross-sectional associations between child and parent. Journal of Activity, Sedentary and Sleep Behaviors, 4(1), Article 2. https://doi.org/10.1186/s44167-025-00072-0

Image Credits: AI Generated

DOI: 10.1186/s44167-025-00072-0

Keywords: childhood obesity, physical activity, sedentary behaviour, accelerometry, parent-child dyads, moderate-to-vigorous physical activity, paediatric health care, Sweden, family-based intervention, intraclass correlation, WHO guidelines, behavioural modelling