Decreasing trend in lean body mass in young Japanese adult women associated with their birth weight

Abstract Despite a 30-year decline in birth weight since 1976 in Japan, the health effects of this decline after a period of growth remain unclear. Lean body mass (LBM) at age 20–21 years was measured annually for 14 years in women with birth years from 1987 to 2001, a period in which a notable birth weight decline was observed in Japan. The birth weight of the participants was obtained from data recorded in the original Japanese Maternal and Child Health Handbook. The participants’ birth weight and the LBM at age 20–21 years significantly decreased during the 14 years of examination; however, fat mass did not decrease during this period. The participants’ LBM significantly correlated with their birth weight. These results suggest that the trend in declining birth weight is manifested as a trend in declining LBM 20 years later. Because low LBM is a risk factor for the development of lifestyle-related diseases such as type 2 diabetes and atherosclerosis, a future increase in these diseases among Japanese women may be anticipated.