MATERNAL ENERGY-BALANCE AND LACTATION PERFORMANCE OF MESOAMERINDIANS AS A FUNCTION OF BODY-MASS INDEX

The effect of maternal energy balance in conjunction with body energy reserves on lactation performance has not been fully elucidated in hum ans. Energy balance was computed from changes in weight and body compo sition over 6 mo postpartum in 21 Otomi Indian women with relatively l ow postpartum body mass indexes (BMIs; in kg/m(2), 21.4 +/- 0.9) and 1 9 with relatively high BMIs (25.7 +/- 1.9). Body fat was determined by deuterium dilution. Milk production was estimated by 24-h test weighi ng. Macronutrient content of human milk was measured by standard techn iques. In both groups weight declined over the 6 mo postpartum (P = 0. 04). In the lower BMI group only, body fat (kg, % of wt) decreased sig nificantly (P = 0.04). Milk fat concentration was positively correlate d with body fat at 3 and 6 mo (r = 0.32 and 0.40; P = 0.04 and 0.01, r espectively). Energy balance was not associated with milk production o r composition, nutrient secretion into milk, or infant growth velocity , except at 6 mo, when energy balance was positively correlated with m ilk energy and fat concentration in the lower BMI group (r = 0.55; P = 0.01). Fat concentration was lower in the lower BMT group (P = 0.04). Because of the inverse correlation between milk production and milk f at at 3 and 6 mo (r = -0.47 and -0.43, respectively; P = 0.01), fat se cretion into milk did not differ between groups. Infant growth velocit ies did not differ significantly between groups. In conclusion, negati ve energy balance in conjunction with lower energy reserves did not ad versely affect lactation performance or infant growth in this populati on of Otomi Indians.