Randomized trial of the short-term effects of dieting compared with dieting plus aerobic exercise on lactation performance

Megan A. McCrory, Laurie A. Nommsen-Rivers, Paul A. Molé, Bo Lönnerdal, Kathryn G. Dewey

Research output: Contribution to journalArticlepeer-review

92 Scopus citations


Background: Limiting postpartum weight retention is important for preventing adult obesity, but the effect of weight loss on lactation has not been studied adequately. Objective: We evaluated whether weight loss by dieting, with or without aerobic exercise, adversely affects lactation performance. Design: At 12 ± 4 wk postpartum, exclusively breast-feeding women were randomly assigned for 11 d to a diet group (35% energy deficit; n = 22), a diet plus exercise group (35% net energy deficit; n = 22), or a control group (n = 23). Milk volume, composition, and energy output; maternal weight, body composition, and plasma prolactin concentration; and infant weight were measured before and after the intervention. Results: Weight loss averaged 1.9, 1.6, and 0.2 kg in the diet, diet + exercise, and control groups, respectively (P < 0.0001) and was composed of 67% fat in the diet group and nearly 100% fat in the diet + exercise group. Change in milk volume, composition, and energy output and infant weight did not differ significantly among groups. However, there was a significant interaction between group and baseline percentage body fat: in the diet group only, milk energy output increased in fatter women and decreased in leaner women. The plasma prolactin concentration was higher in the diet and diet + exercise groups than in the control group. Conclusions: Short-term weight loss (≃1 kg/wk) through a combination of dieting and aerobic exercise appears safe for breast-feeding mothers and is preferable to weight loss achieved primarily by dieting because the latter reduces maternal lean body mass. Longer-term studies are needed to confirm these findings.

Original languageEnglish (US)
Pages (from-to)959-967
Number of pages9
JournalAmerican Journal of Clinical Nutrition
Issue number5
StatePublished - May 1999


  • Adipose tissue mobilization
  • Aerobic exercise
  • Body composition
  • Breast milk
  • Energy expenditure
  • Energy intake
  • Lactation
  • Obesity
  • Prolactin
  • Weight loss
  • Women

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Food Science


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