Lean body mass of well-nourished women is preserved during lactation

Am J Clin Nutr. 1998 Feb;67(2):292-300. doi: 10.1093/ajcn/67.2.292.


To determine whether the lean body mass of well-nourished women was mobilized to support milk protein output during lactation, the body composition of 10 lactating and 10 nonlactating women was examined longitudinally at 6-wk intervals between 6 and 24 wk postpartum and at 52 wk postpartum, and that of 10 nulliparous women was examined at equivalent intervals, by using clinical anthropometry and whole-body potassium counting. Milk production was determined at 6-wk intervals during the period of exclusive breast-feeding (6-24 wk postpartum) by the test-weighing procedure. Milk composition was determined by chemical analysis. Dietary intakes were determined at 6-wk intervals between 6 and 24 wk postpartum from 3-d food records with use of a nutrient database. Lean body mass was maintained in women who exclusively breast-fed their infants during the first 6 mo postpartum while consuming dietary protein in amounts that exceeded those of their nonlactating counterparts by 55%. The high protein intakes were sustained throughout lactation despite a progressive reduction by 32% of milk protein output. Lean body mass was preserved throughout lactation in well-nourished women, suggesting that the metabolic needs of milk protein production were met solely by higher protein intakes of the lactating women.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adipose Tissue / physiology
  • Adult
  • Body Composition
  • Body Mass Index
  • Dietary Proteins / administration & dosage
  • Dietary Proteins / metabolism*
  • Female
  • Humans
  • Lactation / metabolism*
  • Longitudinal Studies
  • Milk Proteins / metabolism
  • Milk, Human / chemistry
  • Muscles / physiology*
  • Nutritional Status
  • Parity
  • Postpartum Period / metabolism


  • Dietary Proteins
  • Milk Proteins