Carbohydrate intolerance that develops or is first recognized during pregnancy is labeled gestational diabetes mellitus. This form of diabetes can significantly affect the mother and fetus during pregnancy and increases the risk of adverse pregnancy-related outcomes. Women who are diagnosed with gestational diabetes have a significant risk of recurrent gestational diabetes in subsequent pregnancies, and a significant number develop type 2 diabetes as they age. The current treatment strategy is to control blood glucose levels through diet and, when needed, insulin therapy. Although insulin therapy has a positive effect on pregnancy outcomes in these patients, it does not address the main issue of insulin resistance.

Exercise programs can benefit patients with diabetes. Aerobic exercise has been shown to decrease insulin needs in patients with gestational diabetes. However, certain exercises may become more difficult to perform in the later stages of pregnancy. The use of resistance exercise might solve some of these issues. In patients with type 2 diabetes, resistance exercise has been shown to improve insulin sensitivity, glucose disposal rate, and glycemic control. Brankston and associates evaluated the effect of circuit-type resistance training on the need for insulin in women with gestational diabetes mellitus.

The trial involved patients who had gestational diabetes mellitus based on established criteria. Inclusion criteria were maternal age between 20 and 40 years, gestational age between 26 and 32 weeks, body mass index below 40 kg per m², being a nonsmoker, and not being involved in a routine exercise program. Participants were assigned randomly to diet alone or diet plus resistance exercise. All participants received dietary instructions on the intake of carbohydrates, proteins, fats, and total calories. The diet-plus-exercise group also was trained in a progressive physical conditioning program by an experienced instructor.

The program involved eight exercises, performed in a circuit manner with a short rest between each station, to be done three times per week. The program started with two sets of 15 repetitions and increased over time. Glucose monitoring was done with portable glucose monitors and performed per protocol. Insulin therapy was started on the basis of established standards and titrated until glycemic control was obtained. The primary outcome assessed was the requirement of insulin in the participants.

Thirty-two women with gestational diabetes mellitus participated in the study. There were no significant differences with regard to physical characteristics between the diet-alone and diet-plus-exercise groups. The two groups did not differ in regard to which patients required insulin therapy. The average number of exercise sessions per week in the diet-plus-exercise group was two. The amount of insulin prescribed was significantly lower and the latency between the first clinic visit and initiation of insulin therapy was longer in the diet-plus-exercise group. The subgroup in the diet-plus-exercise group with a body mass index of more than 25 kg per m² had a significantly lower incidence of insulin use when compared with the same subgroup in the diet-alone group. The two groups were similar when evaluating the gestational age at birth, rate of cesarean deliveries, or fetal birth weight.

The authors conclude that resistance exercise training may help to avoid the use of insulin therapy in overweight women with gestational diabetes mellitus. In addition, exercise can reduce the need for insulin and prolong the latency period to insulin use in these patients.