Adjustments in energy expenditure and substrate utilization during late pregnancy and lactation

Abstract

Background: Metabolic adjustments occur during pregnancy and lactation to support fetal growth and milk synthesis; however, the effect of body composition and hormonal milieu on these changes is poorly understood. Objective: We hypothesized that energy metabolism changes during pregnancy and lactation to support fetal growth and milk synthesis, and that body composition and hormonal milieu influence these alterations. Design: We measured energy expenditure, body composition, and hormone, metabolite, and catecholamine concentrations in 76 women (40 lactating, 36 nonlactating) at 37 wk gestation and 3 and 6 mo postpartum. Total energy expenditure (TEE), basal metabolic rate (BMR), sleeping metabolic rate (SMR), and minimal SMR (MSMR) were measured with room calorimetry. Fatfree mass (FFM) and fat mass were estimated with a 4-component model. Results: TEE, BMR, SMR, and MSMR were 15-26% higher during pregnancy than postpartum after being adjusted for FFM, fat mass, and energy balance. TEE, SMR, and MSMR were higher in lactating than in nonlactating women. Fasting serum insulin, insulin-like growth factor I, fatty acids, and leptin, and 24-h urinary free norepinephrine, epinephrine, and dopamine correlated positively with TEE, BMR, SMR, and MSMR. In nonlactating women, the respiratory quotient decreased over time, carbohydrate oxidation decreased, and fat oxidation increased. Substrate utilization was not influenced by body composition, fasting serum hormones, or 24-h urinary catecholamines. Conclusions: These results indicate increased energy expenditure and preferential use of carbohydrates during pregnancy and lactation. Elevated respiratory quotient and carbohydrate utilization during pregnancy continue during lactation, consistent with preferential use of glucose by the fetus and mammary gland. Am J Clin Nutr 1999;69:299-307.

Energy intake and expenditure of free-living, lactating Colombian women in an urban setting

“…These results are similar to those found in a study of Guatemalan women (Schutz et al, 1980) using the HR method, as well as those found in studies of Swedish (Forsum et al, 1992). North American (Butte et al, 1999), and Gambian women (Singh et al, 1989) using the doubly labeled water method.…”

“…Butte et al, (1999) did, however, report a significantly higher fasting basal respiratory exchange ratio, which they assumed to be linked to the preferential use of glucose by the mammary gland for synthesis of the carbohydrate and protein components of milk.…”

Repeated measurements of energy intake, energy expenditure and energy balance in lactating Bangladeshi mothers

“…Some authors have found a decrease in BMR during lactation (Butte et al, 1997) or during seasonal food shortage (Ategbo et al, 1995) in malnourished women (Ferro-Luzzi et al, 1997), but the apparent decrease disappeared when adjustment was made for body composition. Recent studies have described an enhanced carbohydrate utilization (Butte et al, 1999) and a 5% increase in muscular ef®ciency during lactation (Spurr et al, 1998). The present study was not able to address adaptive effects in relation to lactation.…”

“…Some studies have found a weight loss, corresponding to a fat mass reduction (Forsum et al, 1992;Motil et al, 1998;Butte et al, 1999), and others no change (van Raaij et al, 1990;Goldberg et al, 1991;Lovelady et al, 1995), because of increased energy intake to compensate for lactation. In the present study the women lost weight between 3.5 and 5.5 months postpartum, most of which was fat-free mass, but there was also a reduction in suprailiac skinfold thicknesses.…”

“…Recently, attention has focussed on lactating women and a number of studies have investigated their energy expenditure and body composition (Goldberg et al, 1991;Adair & Popkin, 1992;Forsum et al, 1992;Guillermo-Tuazon et al, 1992;Piers et al, 1995;Dewey, 1998;Butte et al, 1997Butte et al, ,1999Krebs et al, 1997;Motil et al, 1998;Spurr et al, 1998). However there have been few longitudinal studies beyond 6 months post-partum (cf Lawrence et al, 1986) and most of the subjects were well-nourished mothers (van Raaij et al, 1990;Adair & Popkin, 1992;Motil et al, 1998).…”