Teenagers who are either underweight or obese are likely to have fewer children in adulthood, a study by the University of Helsinki has found. Both obesity and an abnormally low body weight are related to reproductive difficulties, and obesity raises the risk of a number of pregnancy complications.
For the study, researchers used data on nearly 1,300 Finnish men and women who were part of a larger study that has tracked their health since 1980. All were between the ages of three and 18 at the study’s outset, and had their body mass index (BMI) measured in adolescence. The study found that adults who had been underweight as teenagers had 10-16% fewer children, compared with those who had a normal BMI in adolescence. Men and women who had been obese as teens had 32-38% fewer children.
Liisa Keltikangas-Jarvinen, who conducted the study, found that there was a long-term effect of teenage BMI, independent of adulthood BMI. This was particularly true of women. For women, an abnormally low BMI can disrupt the menstrual cycle, while obesity can lead to fertility problems. Obesity can, for example, contribute to polycystic ovary syndrome, a cause of infertility.