A new procedure to assess the energy requirements of lactation in Gambian women

The influence of energy metabolism on postpartum weight retention

BACKGROUND

Profiling postpartum energy metabolism may assist in optimizing weight management following childbirth.

OBJECTIVES

The aims of this study were to profile total energy expenditure (TEE), resting energy expenditure (REE), exercise energy expenditure, sleep energy expenditure, and respiratory quotient in women at 3 and 9 mo postpartum (3M-PP, 9M-PP, respectively), and to examine the association between energy metabolism and postpartum weight retention (PPWR).

METHODS

In this cohort study, 1-h REE (measured in a whole body calorimetry unit, WBCU) and body composition (BC, measured by dual-energy X-ray absorptiometry) were measured at 3M-PP and 9M-PP (n = 49). Cardiorespiratory fitness [measured by the predicted maximal volume of oxygen consumption (p$\dot{V}$O2 max), n = 47] and 24-h TEE (WBCU, n = 43) were assessed only at 9M-PP. Women were stratified as high (>4.8 kg) or low (≤ 4.8 kg) weight retainers. Two-way mixed repeated-measures ANOVA and longitudinal regression models were applied. Linear regression was used to generate an equation at 3M-PP from the BC data, to predict the REE at 9M-PP.

RESULTS

The fat mass at 3M-PP was positively associated with PPWR at 3M-PP (mean ± SE β: 0.09 ± 0.03; P = 0.005) and 9M-PP (β: 0.11 ± 0.04; P = 0.008), and negatively associated with REE at 3M-PP (β: -0.16 ± 0.02; P < 0.001) and TEE at 9M-PP (β: -0.15 ± 0.03; P < 0.001). REE was negatively associated with PPWR (β: -0.74; 95% CI: -1.29, -0.19; P = 0.0087). REE was 2 kcal/kg higher in low- vs. high-retainers at 3M-PP, and REE and TEE were both 4 kcal/kg higher in low- vs. high-retainers at 9M-PP. Low-retainers demonstrated an increase in REE greater than expected for changes in BC. PPWR was negatively associated with TEE (β: -0.08 ± 0.02; P = 0.0009) and p$\dot{V}$O2 max (β: -0.02 ± 0.01; P = 0.047); p$\dot{V}$O2 max was 7 mL · kg-1 · min-1 higher in low- vs. high-retainers (P = 0.047).

CONCLUSIONS

Energy metabolism, BC, and cardiorespiratory fitness may be associated with weight regulation and its trajectory during the postpartum period. This provides the foundation for future strategies to promote appropriate postpartum weight management.

Validation of three predictive equations for basal metabolic rate in adults

Objective

To cross-validate three predictive set of equations for basal metabolic rate (BMR) developed by Schofield (Schofield database), Henry (Oxford database) and Cole (Oxford database) using mean values for age, weight, height and BMR of published studies.

Design

Literature review of studies published from 1985 to March 2002.

Setting

All studies selected used appropriate methods and followed conditions that met the criteria established for basal metabolism, were performed in healthy adults, and were not part of the Schofield or Oxford database.

Subjects

A total of 261 groups of men and women from 175 studies were selected and categorised in three age groups (18.5–29.9, 30.0–59.9, ≥60 years old) and three body mass index (BMI) groups (normal weight, overweight and obese).

Results

Linear regression and concordance correlation analysis showed that the three sets of equations had the same association and agreement with measured BMR, across gender, age, and BMI groups. The agreement of all equations was moderate for men and poor for women. The lowest mean squared prediction errors (MSPRs) were given by Henry equations in men and Cole equations in women. Henry and Cole equations gave lower values than Schofield equations, except for men over 60 years of age. Henry equations were the most accurate in men. None of the three equations performed consistently better in women.

Conclusion

These results support the use of Henry equations in men with a wide range of age and BMI. None of the proposed predictive equations seem to be appropriate to estimate BMR in women.

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

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. Fat-free 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.

Total energy expenditure and physical activity level of lactating Mesoamerindians

Energy-sparing mechanisms may be elicited to meet increased energy requirements imposed by lactation on women who reside in poor, rural communities in developing countries. The objectives of this study were to measure total energy expenditure and its components, basal and activity energy expenditure, and to investigate their relationships with lactation performance in a total of 40 rural Mesoamerindians stratified according to postpartum body mass index. Total energy expenditure and fat-free mass were measured by the doubly labeled water method, and basal metabolic rate was determined by indirect calorimetry at 3 and 6 mo postpartum. Physical activity level was taken as the ratio of total energy expenditure to basal metabolic rate. Milk energy output, which is not included in total energy expenditure, was computed from 24-h milk intake (test-weighing) and energy concentration of milk (bomb calorimetry). Anthropometric measurements revealed negligible mobilization of tissue stores. Mean (+/- SD) total energy expenditures were 8912 +/- 1296 kJ/d and 9253 +/- 1298 kJ/d for the lower and higher body mass index groups, respectively. Adjusted for fat-free mass, total energy expenditure was higher in the lower body mass index group (P = 0.05). Adjusted for fat-free mass, basal metabolic rate did not differ between groups. Physical activity level was significantly higher in the lower body mass index group (P = 0.03). Lactation performance did not differ between groups and was not associated with total energy expenditure or its components. Despite the maintenance of energy balance and heightened energy requirements of lactation, energy-sparing mechanisms were not evident in these lactating Mesoamerindians.