A randomized trial of the effects of dieting vs dieting with exercise on lactation performance

M. A. McCrory, L. A. Nommsen-Rivers, P. A. Mole, B. Lonnerdal, K. G. Dewey

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2 Scopus citations


To improve guidelines for weight loss during lactation, the impact of caloric restriction vs caloric restriction with aerobic exercise was studied in healthy, well-nourished exclusively breastfeeding women for 11 d (n = 60; final n=69 by Feb '97). At baseline, subjects were 12 ± 4 wk postpartum, age 32 ± 5 y and 32 ± 6 % fat. Baseline energy needs were determined by 4-d diet (weighed) and activity records (+ indirect calorimetry). The women were then randomly assigned to either a) a diet group (D; energy deficit of 35%); b) a diet plus exercise group (D/E; net energy deficit of 35%, 60% of this by caloric restriction and 40% by additional exercise); or c) a control group (C). All women exercised at least 2 d/wk during baseline; this level was maintained throughout the intervention in the D and C groups. The D/E group exercised 60-90 min/d for 9/11 d during the intervention. Breast milk volume (4-d of test-weighing) and maternal body composition (densitometry) were assessed prior to and during the intervention. Breast milk samples were obtained by 24-h alternate breast expression. Weight loss in the D and D/E groups was 1.9 and 1.6 kg, respectively, compared with only 0.2 kg in the C group (p<0.001). Maternal % body fat decreased by 1.0, 2.1, and 0.6 in the D, D/E and C groups, respectively (p=0.01). Fat-free mass decreased by 0.6 kg in the D group, but increased by 0.5 kg in the D/E group and 0.3 kg in the C group (p=0.006). Change in milk energy output did not differ significantly (+6, 17, and +14 kcal/d; p=0.32), nor did infant weight gain (205, 237, and 66 g; p=0.15) among the D, D/E and C groups, respectively. These results indicate that short-term weight loss of up to about 1.2 kg/wk is compatible with lactation, but that to preserve lean tissue this weight loss should be achieved by a combination of caloric restriction and a high level of aerobic exercise.

Original languageEnglish (US)
JournalFASEB Journal
Issue number3
StatePublished - 1997

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Cell Biology


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