Exercise protects against glucose intolerance in individuals with a small body size at birth

Background. Small body size at birth is a risk factor for Type 2 diabetes. We investigated whether regular exercise is related to lower rates of glucose intolerance in individuals with a small body size at birth and whether birth size affects exercise habits in adulthood. Methods. Five hundred subjects aged 65–75 years with data on birth measurements underwent an oral glucose tolerance test. They reported their weekly exercise frequency and intensity and yearly physical leisure time activity. Results. Frequent (≥3/week) or moderate weekly exercise and yearly physical activity were all related to lower rates of glucose intolerance. This effect was, however, dependent on birth size, being strongest among subjects with a small body size at birth (birth weight ≤3000 g and/or ponderal index ≤26 kg/m3). Among men, frequency (P = 0.033) and intensity (P = 0.030) of exercise as well as yearly physical activity (P = 0.005) correlated inversely with birth size. Conclusions. Subjects predisposed to Type 2 diabetes due to a small birth size are strongly protected from glucose intolerance by regular exercise. Although a small body size at birth is related to a smaller muscle mass in adulthood, men born thin exercised more in adulthood than those not born thin. In these elderly subjects this might indicate the survival of the fittest.