Body, Baby, and Breastfeeding: the effects of exercise on milk supply

Joanna Hess PT, DPT, PRC, WCS

tilt shift lens photo of infant s hand holding index finger of adult
Photo by Dominika Roseclay on Pexels.com

Breastfeeding, for all its two-way benefits, requires the mother to share her body and she often ends up feeling like the health of the baby comes at the cost of her well-being—physical, mental, and social. Physical activity improves all three realms for the mother but activity may be postponed because of the assumption that it will negatively affect the baby’s growth. Can a mother have it all–breastfeed a growing baby and get return to pre-baby weight? Multiple studies and reviews show that moderate physical activity and weight loss does not negatively impact milk supply or infant growth.

Should intentional weight loss be considered during the postpartum period?

Yes, for most mothers. At one year postpartum, about one in six women retains 10 pounds or more of weight gained during pregnancy. The weight gain during and after pregnancy often stays with the mother into post-childbearing years setting up for metabolic diseases and orthopedic complications (10). While moderate physical activity itself is not sufficient for postpartum weight loss (6), physical activity remains an integral part of restoring the body’s set point in conjunction with dietary modifications. Moderate physical activity influences maternal health not only through weight control but also mental wellbeing, bone health (9), functional tolerance, sleep quality, and establishing family patterns of recreation. Breastfeeding itself requires high levels of energy, 300-600 kcal/day (5), and is associated with improved postpartum weight management long-term over 24 months (2), but not short term within 3 months (4).

Does exercise for intentional weight loss affect milk supply?

No, for most mothers. However, when breastmilk is the sole source of nutrition, a fussy baby protesting or rejecting a feed can be worrisome. Multiple studies have shown that exercise is not related to decreased milk supply, milk quality, or infant growth (1, 3, 6). Some studies show that over time, moderate exercise is related to increased milk supply (7). Some babies show a distaste for post-exercise breast milk. Lactic acid produced in vigorous levels of exercise may be associated with a decreased acceptance of breastmilk (8), but it resolves within 30-60 minutes of exercise (1, 13). Weight loss in most situations, but particularly while breastfeeding, should not exceed 0.75-1 pound/week (6, 9, 12). Wait until milk supply is established for more aggressive caloric restriction.

  • Intensity: Most studies evaluate moderate exercise intensity, roughly measured as the ability to talk, but not sing during the activity. Depending on the mother’s fitness level, the activity varies from walking to jogging. Vigorous activity is cautioned mainly because of the lactic acid buildup that is associated with poorer baby nursing.
  • Duration and frequency: 45 minutes, 5 days/week for cardiovascular. 30 minutes, 3-4 day/s week for resistance training (6).

If not exercise, what else affects milk supply?

Despite the normalcy and frequency of breastfeeding, we have yet to fully understand the complexity of the mechanism to regulate calories and nutrition, to replenish based on need, and what can increase or decrease milk supply. While baby’s quantity and quality of nursing most directly affects supply, more subtle influences like maternal food and liquid intake, exercise, sleep quantity and quality, cortisol slopes (11) also contribute to short term milk supply fluctuations.

Anything else before squeezing into the WunderUnders?

  • Fatigue. At 6 weeks postpartum, the majority of mothers do not yet have their normal level of energy (9) making additional activity difficult and almost incomprehensible to include into long days. Physical activity is only one part of wellness in the postpartum period.
  • Fussy baby. Full breasts contribute to uncomfortable and leaky exercise. If possible, feed your baby before heading off to exercise. Clean off the sweat after exercise, wait for 30 minutes if your baby seems fussy after exercise.
  • Good fitting bra. The balance of support for comfort and managing compression to protect milk ducts is the goal for your sports bra. Take off your bra when feeding to allow for complete emptying of the breasts and maintaining supply.
  • Hydration. Although hydration is more important for mother thirst than milk supply, increase fluid intake during and after exercise by about 1 liter (5). Attend to the thirst signal.
  • Baby and mother health. Although studies show that physical exercise does not detrimentally affect infant growth nor maternal health, consult with your healthcare practitioner if baby or mother aren’t following expected patterns.

A postpartum exercise plan should be a gradual and systematic return to previous level of activity. The physical therapists at Beyond Basics Physical Therapy safely guide women through this postpartum period to address multiple factors in recovery and return to fitness.

REFERENCES

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2 da Silva MD, Oliveira Assis AM, Pinheiro SM, de Oliveira LP, da Cruz TR. Breastfeeding and maternal weight changes during 24 months post‐partum: a cohort study. Maternal & child nutrition. 2015 Oct;11(4):780-91.

3 Daley AJ, Thomas A, Cooper H, Fitzpatrick H, McDonald C, Moore H, Rooney R, Deeks JJ. Maternal exercise and growth in breastfed infants: a meta-analysis of randomized controlled trials. Pediatrics. 2012 Jul 1;130(1):108-14.

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8 Mortensen K, Kam R. Exercise and breastfeeding. Breastfeeding Review. 2012 Nov;20(3):39.

9 Mottola MF. Exercise in the postpartum period: practical applications. Current sports medicine reports. 2002 Dec 1;1(6):362-8.

10 Nascimento SL, Pudwell J, Surita FG, Adamo KB, Smith GN. The effect of physical exercise strategies on weight loss in postpartum women: a systematic review and meta-analysis. International Journal of Obesity. 2014 May;38(5):626.

11 Straub H, Simon C, Plunkett BA, Endres L, Adam EK, Mckinney C, Hobel CJ, Thorp JM, Raju T, Shalowitz M. Evidence for a complex relationship among weight retention, cortisol and breastfeeding in postpartum women. Maternal and child health journal. 2016 Jul 1;20(7):1375-83.

12 Thein-Nissenbaum J. The postpartum triathlete. Physical Therapy in Sport. 2016 Sep 1;21:95-106.

13 Wright KS, Quinn TJ, Carey GB. Infant acceptance of breast milk after maternal exercise. Pediatrics. 2002 Apr 1;109(4):585-9.