Written by Cheryl Lovelady, Ph.D., M.P.H., R.D.
The American College of Obstetricians and Gynecologists recommends women resume physical activity after delivery as soon as it is physically and medically safe (1). In addition, the American Academy of Pediatrics recommends that all women breastfeed their infants during the first year of life (2). Therefore, the effect of exercise on milk volume and composition, and consequently infant growth and health, must be considered. Results of studies with lactating women suggest that exercise improves aerobic fitness, plasma lipids and insulin response and does not affect breast milk composition and volume, or infant growth (3, 4). In these studies, the following exercise protocol was used:
- Exercise began at four to six weeks postpartum, after women received medical clearance from their physicians.
- Exercise sessions were initially 15 minutes, then were increased by two minutes every day until women were exercising (walking, jogging or aerobic dancing) for 45 minutes per day, four to five days per week. Since the physiological changes of pregnancy continue for four to six weeks postpartum, women should begin exercising gradually.
In addition to the benefits of aerobic exercise, we recently reported the beneficial effects of resistance training on bone mineral density in lactating women (5). During lactation, approximately 200 mg of calcium is transferred to breast milk each day. This results in a three to nine percent loss of bone mineral density in the lower lumbar spine. Bone mass usually returns to prepregnancy levels when the infant is weaned, but not in all women. We randomly assigned exclusively breastfeeding, sedentary women at four weeks postpartum to either an exercise group which consisted of aerobic exercise and resistance exercise three days per week or a sedentary group. After 16 weeks, the exercise group lost 4.8 percent of their lumbar spine bone mineral density, compared to seven percent in the sedentary group.
While exercise improves health status, exercise alone – without calorie restriction – does not promote weight (3, 4). Therefore, we investigated the effect of a ten-week energy restriction and exercise program on infant growth in overweight, exclusively breastfeeding women at four weeks postpartum (6). Our results suggest that once lactation is established, overweight women may restrict energy intake by 500 kcal per day to promote a weight loss of 0.5 kg per week without affecting infant growth. While these studies have determined the safety and efficacy of moderate exercise and calorie restriction during lactation, further research is needed to determine the most effective way to implement these lifestyle changes during the postpartum period.
Additional information on exercise postpartum:
ACSM Roundtable Consensus Statement: Impact of Physical Activity During Pregnancy and Postpartum on Chronic Disease Risk
Guidelines and tips from the American Pregnancy Association
Information from kidshealth.org
1. American College of Obstetricians and Gynecologists Committee. Opinion no. 267: Exercise during pregnancy and the postpartum period. Obstet Gynecol. 2002;99:171-3.
2. American Academy of Pediatrics. Breastfeeding and the use of human milk. Ped. 1997;100:1035-39.
3. Lovelady CA, Nommsen-Rivers LA, McCrory MA, Dewey KG. Effects of exercise on plasma lipids and metabolism of lactating women. Med Sci Sports Exerc. 1995;27:22-8.
4. Dewey K.G., Lovelady C.A., Nommsen-Rivers L.A., McCrory M.A., and B. Lonnerdal. A randomized study of the effects of aerobic exercise by lactating women on breast-milk volume and composition. N. Engl. J. Med. 1994; 330:449-453.
5. Lovelady, C.A., Bopp, M.J., Colleran, H.L., Mackie, H.K., and L. Wideman. Effect of exercise training on loss of bone mineral density during lactation. Med Sci Sports Exer 2009;41:1902-07.
6. Lovelady CA, Garner KE, Moreno KL, Williams JP. The effect of weight loss in overweight, lactating women on the growth of their infants. N Eng J Med. 2000;342:449-53.