ESPE Yearbook of Paediatric Endocrinology

To read the full abstract: Sci Rep 2018; 8(1):369

The effect of improving socio-economic conditions on growth has been well described in Europe in the 19^th and 20^th centuries. For instance, in Norway, height increased by 0.3 cm every 10 years between 1830-1875 and then by 0.6 cm every 10 years between 1875-1930. However, the respective roles of nutrition and physical activities has not been clarified.

The authors present their work as an almost pure natural experiment of the role of physical activity on growth in children. Indeed, over 20 years, in a small remote community in South East Mexico, major changes took place, including introduction of mechanised farming, road access to the community and availability of running water. This led to a decrease in physical activity (e.g. less work on the farm) and to an increase in sedentarity (e.g. more time at school) in the children of this community. The authors however acknowledge that calorie intake, which was not measured, likely increased, although nutrition remained largely traditional with little influence of market food. Their main conclusion is that reduced physical activity was associated with greater increases in weight and height. The most likely interpretation was that those calories that are not burned by physical activity become available for growth and for fat deposition. There are however several important points to remember. First, in contrast to populations in high-income countries, overweight and obesity were virtually non-existent in this small Mexican community. Hence, these results may not apply to high-income countries where caloric intake is usually much greater than the minimum required for growth. Second, energetic trade-offs may not be the only explanation for the effect of physical activity on growth. For instance, physical activity also affects body composition, sleep, mental health and, relevant to the pediatric endocrinologist, hormone secretion. Third, the changes observed over 20 years (water, electricity, roads) may have other consequences that indirectly affect growth, such decreased infectious load (see 13.24). Finally, only prepubertal children were studied, so that the effect of physical activity on growth can not be extrapolated to adult height and weight. Nevertheless, this study emphasizes the need for additional studies on the likely multifactorial effects of physical activity on growth.