Is milk production impaired by dieting during lactation?

To determine the feasibility of a weight-loss program during lactation, 33 healthy, well-nourished, breast-feeding women were enrolled. Twenty-two women completed the 10-wk study, losing a mean (+/- SD) of 4.8 +/- 1.2 kg. Mean energy intake during the study was nearly 2.25 MJ (538 kcal) below the mean daily baseline intake of 9.64 +/- 2.48 MJ (2303 +/- 592 kcal). The sum of three maternal skinfold thickness, waist, and hip measurements were significantly smaller (P = 0.0001) at study completion. Mean daily milk production was 759 +/- 142 mL/d at baseline and 802 +/- 189 mL/d at week 10. The infants gained an average of 21 g/d, or 1.48 +/- 0.40 kg overall. The mean percent fat of milk at baseline and 10 wk was 4.06 +/- 2.15 and 4.00 +/- 2.56, respectively. The mean daily nitrogen content of milk at baseline and study completion was 1.82 +/- 0.32 and 1.62 +/- 27 g/L. These findings suggest that modest weight loss by healthy breast-feeding women does not adversely affect either quantity or quality of milk consumed by their infants.