Objective: Pregnancy and exercise have opposite effects on fat mass and insulin resistance. We therefore designed this study to test the hypotheses that exercise during pregnancy alters the pregnancy- associated increases in the levels of tumor necrosis factor alpha and leptin and that the changes in tumor necrosis factor alpha and leptin concentrations during pregnancy continue to reflect changes in fat mass.
Study design: The levels of tumor necrosis factor alpha and leptin were measured longitudinally in a control group of physically active women, a group of women who performed endurance exercises >/=4 times a week throughout pregnancy, and a group of women who initially performed endurance exercises but then stopped exercising during midpregnancy. Exercise was monitored, and longitudinal estimates of maternal total mass and fat mass were obtained.
Results: Tumor necrosis factor alpha levels were lower during pregnancy in the women who exercised, and the same was true for leptin levels. When women stopped exercising, however, both tumor necrosis factor alpha and leptin concentrations rose at rates comparable to those seen in the physically active control group. Changes in leptin concentration but not those in tumor necrosis factor alpha concentration correlated with the pregnancy-associated increases in total body and fat mass.
Conclusions: Regular weight-bearing exercise during pregnancy suppresses the pregnancy-associated changes normally seen in both tumor necrosis factor alpha and leptin. The decrease in leptin reflects decreased fat accretion, and we speculate that the changes in tumor necrosis factor alpha may reflect a change in insulin resistance.