"From growth in height to growth in breadth": the changing body shape of Swiss conscripts since the late 19th century and possible endocrine explanations

Abstract

Because Swiss conscription has been mandatory and standardized since 1875 and measurement procedures for height and weight have not changed, recruitment data (representative for 80-100% of the living young men) provide a solid foundation for a detailed study of changes of young men in Switzerland over the past 140 years. The average Swiss body height increased markedly by 15 cm between the 1870s and the 1970s (birth years). Improvements in living conditions are likely to have been among the main environmental determinants of this increase, but there are other likely candidates, all of which worked via the endocrine system. First, widespread iodine deficiency at the end of the 19th century helps to account for an overrepresentation of very short conscripts, for the low level of average height in Switzerland in general as well as for the tremendous regional variation in average height. Second, the doubling of annual per capita milk consumption between 1875 and 1900 was probably a key factor in the height increase, operating directly on IGF-1 concentration. Third, public-health measures, such as the iodine-deficiency prophylaxis via weekly iodine tablets for schoolchildren and via iodized table salt, introduced in the 1920s, may have been largely responsible for the dramatic increase in height during the interwar period. Since the 1970s (birth years), the positive height trend slowed down, body shape in Switzerland has evolved from growth in height to growth in breadth. Precisely how today's complex of genetic, epigenetic, environmental, and endocrine factors limiting height growth and promoting body breadth and excess weight operates has yet to be completely understood.