Energy requirements during pregnancy based on total energy expenditure and energy deposition

Walking for health in pregnancy: assessment by indirect calorimetry and accelerometry

The purpose of this study was to examine RT3 accelerometer activity counts and activity energy expenditure of 36 pregnant women at 20 and 32 weeks' gestation during treadmill walking and free-living conditions. During treadmill walking, oxygen consumption was collected, and activity energy expenditure was estimated for a 30-min walk at a self-selected walking pace. The number of min it would take a pregnant woman to meet exercise recommendations (i.e., kcal/week) were calculated. Preliminary activity count cut points at a self-selected walking pace were then estimated and applied in interpreting free-living data. For the treadmill walking condition, the self-selected walking pace significantly decreased from 20 to 32 weeks' gestation. Additionally, few women (< 12% each day) met physical activity guidelines in the free-living condition. Encouraging pregnant women to walk for 30-40 min per day at a self-selected walking pace may be an appropriate public health recommendation.

Overweight and obesity doubled over a 6-year period in young women living in poverty in Mexico

OBJECTIVE

To document the changes in BMI and the prevalence of overweight and obesity in young women living in poverty in a semi-urban community in Mexico.

METHODS AND PROCEDURES

Women who had previously participated in a longitudinal research study (1997-2000) were re-assessed in 2005. Anthropometric measurements were obtained using standard procedures, and socio-demographic questionnaires were administered. Total and annual rate of change in BMI and change in the prevalence of overweight and obesity (BMI > or = 25.0 and > or =30.0) were estimated.

RESULTS

Mean age in 2005 was 30.0 +/- 5.7 years (n = 683) and time between recruitment and follow-up was 6.4 +/- 1.0 years. Mean change in BMI was +3.6 +/- 2.7 (range -8.2 to +14.6). In 2005, 500 (73.2%) women were overweight, up from 263 (38.5%) in the original assessment. The prevalence of obesity tripled over the follow-up period (from 9.8% to 30.3%). The mean annual rate of change in BMI was +0.6 (+/-0.4). After adjustment for age and parity at baseline, an annual rate of change of BMI above the sample median (>0.5) was associated with lower levels of formal education.

DISCUSSION

The annual increase in the prevalence of overweight and obesity in this sample is double that which was reported at a national level in Mexico. An understanding of the determinants of this rapid increase among the women living in poverty in Mexico is urgently needed.

[A Longitudinal study of body composition and basal metabolic rate during pregnancy in a black population of Kinshasa, Democratic Republic of Congo (RDC)]

OBJECTIVE

A longitudinal study of body composition and basal metabolic rate during pregnancy in a black population of Kinshasa.

MATERIALS AND METHODS

Body composition and basal metabolic rate were determined by bioimpedance, and energy intake was evaluated using the 24 h recall method at 20, 34 and > 37 weeks of gestation in 76 black, Congolese women. The subjects had to be healthy, and to deliver term, singleton infants after a normal pregnancy.

RESULTS

At 20 weeks of pregnancy, the 76 women, aged 28.5+/-6.4 years, had a body weight of 61.1+/-7.7 kg, a body mass index of 23.0+/-3.8 kg/m(2), a fat mass of 36.6+/-6.8% and a basal metabolic rate of 1399+/-84 kcal/24 h. Subsequently, increases in body weight (+6.5 kg), fat-free mass (+ 5.1 kg), body water (+4.4 l) and basal metabolic rate (+297 kcal/24 h) (P < 0.0001) were observed. The increase in fat mass (+1.4 kg) was less pronounced. Energy intake was stable.

CONCLUSION

Changes in body composition during pregnancy in Congolese black women are comparable to those reported in other populations. Pre- and per-gravidic fat mass is higher in congolese women than in Caucasian women.

Activity levels in pregnant New Zealand women: relationship with socioeconomic factors, well-being, anthropometric measures, and birth outcome

Activity during pregnancy has health implications for mother and child. The aim of this prospective cohort study was to examine changes in activity levels during pregnancy; the influence of socioeconomic factors and well-being on activity, and the influence of activity on maternal anthropometric measures and birth outcome. Twenty-four hour activity diaries were collected for 3 d in months 4 and 7 of pregnancy in 197 volunteers. Anthropometric measures and questionnaires to determine personal details were collected at these times and 2 months post-partum. Health records were used to supply infant measures. The time spent on each activity category was calculated, and used to calculate overall daily metabolic equivalents (METs). Low socioeconomic (SES) group 24 h activity levels were significantly higher than for high SES or welfare groups (p = 0.013). Activity declined throughout pregnancy in all groups (p = 0.002). Women with children had higher 24 h activity, spending 41% more time walking and (or) on housework than nulliparous women (p = 0.013). Reduced well-being was associated with lower levels of activity. Sleep and lying down time influenced 2 month post-partum body mass (upper quartile gained 2.54 kg, lower quartile lost 0.24 kg, p < 0.001). Mean infant gestational age increased with increasing 24 h activity (p = 0.047). No infants were born prematurely to mothers who spent more than 190 min/d walking or doing housework activities in month 4. Probability of infant admission to the neonatal intensive care unit (NICU) declined with time spent walking or doing housework in month 4 (p = 0.007). Mean (SE) birth weight was 3883 (+/-165) g in the 10% of women spending less than 530 min sleeping or lying down per day, compared with 3413 (+/-104) g in the 10% of women spending 725 min or more sleeping or lying down. Socioeconomic factors were therefore important influences on activity levels during pregnancy. Inactivity, especially in early pregnancy, was associated with more maternal weight retention at 2 months post-partum and a greater probability of admission to NICU and premature delivery.

Obesity in neurobiology

Obesity reflects an imbalance between energy uptake and expenditure that is mediated by behavior. Obesity is a growing epidemic and a major risk factor for neurobiological diseases like stroke, dementia, intracranial hypertension and sleep disorders. Conversely, obesity can also be induced by neurobiological disorders and drugs. The etiology of obesity is complex and includes biology, behavior and environment. Physicians are faced with the need to manage obesity while strategies for prevention and sustained weight reduction are limited. Present treatment options comprise lifestyle modification, diet, pharmacotherapy and bariatric surgery. Considerable headway has been made into elucidating the neurobiological underpinnings of obesogenic behavior. There is now a growing understanding of the metabolic, hormonal and behavioral circuitries that contribute to the complex and redundant system for energy balance. Changing the net balance of this system to prevent or reduce obesity requires multimodal and long-term interventions.

Energy Metabolism During Human Pregnancy

This review summarizes information regarding how human energy metabolism is affected by pregnancy, and current estimates of energy requirements during pregnancy are presented. Such estimates can be calculated using either increases in basal metabolic rate (BMR) or increases in total energy expenditure (TEE). The two modes of calculation give similar results for a complete pregnancy but different distributions of energy requirements in the three trimesters. Recent information is presented regarding the effect of pregnancy on BMR, TEE, diet-induced thermogenesis, and physical activity. The validity of energy intake (EI) data recently assessed in well-nourished pregnant women was evaluated using information regarding energy metabolism during pregnancy. The results show that underreporting of EI is common during pregnancy and indicate that additional longitudinal studies, taking the total energy budget during pregnancy into account, are needed to satisfactorily define energy requirements during the three trimesters of gestation.

Assessment of physical activity and energy expenditure in epidemiological research of chronic diseases

Physical inactivity has emerged as an important risk factor for a number of diseases, but the typically crude exposure assessments in epidemiological studies, with entailing variation in measurement accuracy, may be a source of heterogeneity contributing to inconsistent results among studies. Consequently, the choice of method for the assessment of physical activity in epidemiological studies is important. Good methods increase our chances of avoiding misclassification and may enhance our understanding of the association between physical activity and health. Since physical activity is also a potential confounder of other lifestyle-health relationships, good methods may enhance our ability to control for confounding. But despite a steadily increasing selection of methods to choose from, no method is suitable for every situation and every population. Although the questionnaire is the most widely used method in epidemiological studies, and laboratory methods are mainly used for validation purposes, improved technology may change our ways of assessing physical activity in the future. This paper describes different methods to measure physical activity and energy expenditure from the epidemiological perspective, and attempts to address the concepts related to the measurement of physical activity.

Management of obesity in pregnancy

Maternal pregravid obesity is a significant risk factor for adverse outcomes during pregnancy. In early pregnancy there is an increased risk of spontaneous abortion and congenital anomalies. In later gestation maternal metabolic manifestations of the metabolic syndrome, such as gestational hypertensive disorders and diabetes, become clinically recognized because of the increased insulin resistance in obese compared with nonobese women. In women with pregestational glucose intolerance, hypertension, central obesity, and lipid disorders, the physiologic changes in pregnancy increase the risk of problems previously not routinely encountered during pregnancy. These include chronic cardiac dysfunction, proteinuria, sleep apnea, and nonalcoholic fatty liver disease. At parturition the obese patient is at an increased risk of cesarean delivery and associated complications of anesthesia, wound disruption, infection, and deep venous thrombophlebitis. For the fetus there are short-term risks of fetal macrosomia, more specifically obesity, and long-term risks of adolescent components of the metabolic syndrome. Although preliminary results of bariatric surgery are encouraging, the procedure is expensive and not for all obese women, and we recognize that long-term follow-up data on offspring of obese women who have undergone bariatric surgery before pregnancy are lacking. In the interim, we need to encourage obese women to lose weight before conception, using lifestyle changes if possible. During pregnancy, weight gain should be limited to Institute of Medicine guidelines (currently under review) and encouragement given for physical activity.

Energy requirements during pregnancy and lactation

Objective

To estimate the energy requirements of pregnant and lactating women consistent with optimal pregnancy outcome and adequate milk production.

Design

Total energy cost of pregnancy was estimated using the factorial approach from pregnancy-induced increments in basal metabolic rate measured by respiratory calorimetry or from increments in total energy expenditure measured by the doubly labelled water method, plus energy deposition attributed to protein and fat accretion during pregnancy.

Setting

Database on changes in basal metabolic rate and total energy expenditure during pregnancy, and increments in protein based on measurements of total body potassium, and fat derived from multi-compartment body composition models was compiled. Energy requirements during lactation were derived from rates of milk production, energy density of human milk, and energy mobilisation from tissues.

Subjects

Healthy pregnant and lactating women.

Results

The estimated total cost of pregnancy for women with a mean gestational weight gain of 12.0 kg, was 321 or 325 MJ, distributed as 375, 1200, 1950 kJ day-1, for the first, second and third trimesters, respectively. For exclusive breastfeeding, the energy cost of lactation was 2.62 MJ day-1 based on a mean milk production of 749 g day-1, energy density of milk of 2.8 kJ g-1, and energetic efficiency of 0.80. In well-nourished women, this may be subsidised by energy mobilisation from tissues on the order of 0.72 MJ day-1, resulting in a net increment of 1.9 MJ day-1 over non-pregnant, non-lactating energy requirements.

Conclusions

Recommendations for energy intake of pregnant and lactating women should be updated based on recently available data.

Plasma adiponectin concentrations in non-pregnant, normal and overweight pregnant women

AIMS

Adiponectin is an adipokine that has anti-diabetic, anti-atherogenic, anti-inflammatory and angiogenic properties. This hormone has been implicated in both the physiological adaptation to normal pregnancy and in obstetrical complications. The aims of this study were to determine normal maternal plasma concentrations of adiponectin throughout gestation and to explore the relationships between plasma adiponectin concentration, pregnancy, and maternal overweight.

METHODS

A cross-sectional study was designed to include normal pregnant (normal weight and overweight; 11-42 weeks of gestation), and non-pregnant women. Plasma adiponectin concentration was determined by immunoassay. Non-parametric statistics were used for analysis.

RESULTS

(1) Adiponectin was detectable in the plasma of all patients; (2) there was no significant differences in the median adiponectin concentration between pregnant and non-pregnant women; (3) plasma adiponectin concentrations were negatively correlated with gestational age only among normal weight pregnant women; and (4) overweight patients had significantly lower plasma adiponectin concentrations than normal weight women.

CONCLUSIONS

Consistent with the increased insulin resistance and weight gain that occur in pregnancy, adiponectin concentrations were negatively correlated with gestational age. The results of this study and the nomogram herein presented, can serve as the basis to explore the relationship between adiponectin and pregnancy complications and facilitate the clinical use of this important adipokine.

Resistin: a hormone which induces insulin resistance is increased in normal pregnancy

AIMS

Resistin, a newly discovered adipokine, is thought to play a key role in the regulation of insulin resistance. The objectives of this study were to develop a nomogram of maternal plasma concentrations of resistin from 11 weeks of gestation to term and to determine whether resistin concentrations differ between normal and overweight pregnant women.

METHODS

In this cross-sectional study, plasma concentrations of resistin were determined in normal pregnant women of normal body mass index (BMI 18.5-24.9; n=261), overweight pregnant women (BMI > or =25; n=140), and non-pregnant women of normal BMI (n=40). Blood samples were collected once from each woman between the first trimester and term. Percentiles for resistin concentration were determined for five pre-specified windows of gestational age. Plasma resistin concentration was determined by immunoassay. Non-parametric statistics were used for analysis.

RESULTS

The median maternal plasma concentration of resistin between 11 to 14 weeks of gestation in women of normal weight was significantly higher than non-pregnant women; the plasma concentration of resistin increased with gestational age.

CONCLUSIONS

Normal pregnant women have a higher median plasma concentration of resistin than non-pregnant women and the concentration of this adipokine increases with advancing gestation. Alterations in the maternal plasma concentration of resistin during pregnancy could contribute to metabolic changes of pregnancy.

Blood ketone monitoring: a comparison between gestational diabetes and non-diabetic pregnant women

AIM

To measure ketonemia in a control population of pregnant women and in a population of women with gestational diabetes (GDM). To define a normal ketonemia threshold for the controls and to determine whether or not this value could play a role in the clinical management of women with GDM.

METHOD

Fifty-six women with a normal OGTT and 49 women with GDM were included and monitored from the 25th to the 37th week of pregnancy. Control subjects agreed to perform glycaemia and ketonemia self-monitoring 3 times a day. In addition, women with GDM were asked to measure their postprandial glycaemia. Glycaemia and ketonemia measurements were performed using Optium meters. Subjects kept a 24-hour food record twice a week.

RESULTS

The mean ketonemia was lower in the control group than in the GDM group (0.01+/-0.10 vs. 0.04+/-0.009 mmol/l; P<0.001). Ketonemia values measured before the midday meal and prior to the evening meal were lower for control subjects than for GDM patients (P=0.002 and P=0.005). Fasting ketonemia was unrelated to ketonuria in the GDM group, whereas there was a correlation in the control group (P=0.006). At least one chronic increase in ketonemia levels was observed in 47% of the women with GDM, compared with only 12% of controls. The lowest levels of evening glycaemia correlated with the highest levels of ketonemia; women with GDM reported lower food and carbohydrate intakes than controls (P<0.001).

CONCLUSION

This work has enabled the establishment of ketonemia reference standards in non-diabetic pregnant women. If ketonemia does indeed indicate overly restrictive dietary behavior, this parameter could be employed for monitoring adherence to the nutritional recommendations for GDM.

Maternal obesity, metabolism, and pregnancy outcomes

About one third of all pregnant women in the United States are obese. Maternal obesity at conception alters gestational metabolic adjustments and affects placental, embryonic, and fetal growth and development. Neural tube defects and other developmental anomalies are more common in infants born to obese women; these defects have been linked to poor glycemic control. Preeclampsia, a gestational disorder occurring more frequently in obese women, appears to be due to a subclinical inflammatory state that impairs early placentation and development of its blood supply. Fetal growth and development during the last half of pregnancy depends on maternal metabolic adjustments dictated by placental hormones and the subsequent oxygen and nutrient supply. Maternal obesity affects these metabolic adjustments as well. Basal metabolic rates are significantly higher in obese women, and maternal fat gain is lower, possibly in response to altered leptin function. The usual increase in insulin resistance seen in late pregnancy is enhanced in obese mothers, causing marked postprandial increases in glucose, lipids, and amino acids and excessive fetal exposure to fuel sources, which in turn increases fetal size, fat stores, and risk for disease postnatally. Impaired glucose tolerance, gestational diabetes, and hyperlipidemia are more common among obese mothers. To date, little attention has been given to the role of diet among obese women in preventing these problems. However, studies of women with impaired glucose tolerance show that replacing refined carbohydrates and saturated fat with complex, low-glycemic carbohydrates and polyunsaturated fatty acids improves metabolic homeostasis and pregnancy outcomes. Thus, current dietary guidelines regarding the amount and type of carbohydrates and fat for nonpregnant women seem appropriate for pregnant women as well.

Total serum vitamin C concentration in pregnant women: implications for a healthy pregnancy

OBJECTIVES: total serum vitamin C (L-ascorbic acid) concentration was measured in 90 pregnant women, 30 in each trimester (age range 18-35 years) and a control group of age-matched non-pregnant women. METHODS: total serum vitamin C concentration was measured using the 2.4-dinitrophenylhydrazine method which involves the conversion of vitamin C to dehydroascorbic acid in the presence of copper (II) ions and subsequent measurement of the resulting bis-hydrazone at 540nm. RESULTS: the total vitamin C concentration in the first trimester was 2.55 ± 0.82 mg/dl and 2.32 ± 0.40 mg/dl and 0.77 ± 0.10 mg/dl in the second and third trimesters respectively. Relative to serum total vitamin C concentration in the controls (3.15 ± 0.13 mg/dl) these values are significantly lower (p < 0.05). CONCLUSIONS: low serum vitamin C in pregnancy may indicate utilization of this vitamin to mop up the excess reactive oxygen species and maintain its normal homeostasis. Therefore, Vitamin C supplementation during pregnancy is recommended in order to boost the body's low vitamin C level and prevent the predisposition to low birth weight babies, premature delivery and pre-eclamsia all of which are known to be associated with sub-optimal vitamin C levels during pregnancy.

Regulation of maternal metabolism by pituitary and placental hormones: roles in fetal development and metabolic programming

This review outlines the regulation of maternal metabolism by hormones, cytokines and growth factors, highlighting recent studies that implicate disordered somatolactogen signalling in the pathogenesis of perinatal growth failure and the development of the metabolic syndrome.

Activity pattern and energy expenditure due to physical activity before and during pregnancy in healthy Swedish women

Human pregnancy is associated with increased requirements for dietary energy and this increase may be partly offset by reductions in physical activity during gestation. Studies in well-nourished women have shown that the physical activity level (PAL), obtained as the total energy expenditure (TEE) divided by the BMR, decreases in late pregnancy. However, it is not known if this decrease is really caused by reductions in physical activity or if it is the result of decreases in energy expenditure/BMR (the so-called metabolic equivalent, MET) for many activities in late pregnancy. In the present study activity pattern, TEE and BMR were assessed in twenty-three healthy Swedish women before pregnancy as well as in gestational weeks 14 and 32. Activity pattern was assessed using a questionnaire and heart rate recording. TEE was assessed using the doubly labelled water method and BMR was measured by means of indirect calorimetry. When compared to the pre-pregnant value, there was little change in the PAL in gestational week 14 but it was significantly reduced in gestational week 32. Results obtained by means of the questionnaire and by heart rate recording showed that the activity pattern was largely unaffected by pregnancy. The findings support the following conclusion: in a population of well-nourished women where the activity pattern is maintained during pregnancy, the increase in BMR represents approximately the main part of the pregnancy-induced increase in TEE, at least until gestational week 32.

Biomedical Research on Health and Performance of Military Women: Accomplishments of the Defense Women's Health Research Program (DWHRP)

In 1994, Congress provided dollar 40 M for biomedical research on issues of importance for military women. This supported 104 intramural and 30 extramural studies and launched an era of research to narrow the knowledge gap on protection and enhancement of health and performance of military women. Projects addressed issues specific to female physiology (e.g., gynecological health in the field, maternal malaria), problems with higher prevalence for women (e.g., marginal iron deficiency, stress fracture), and issues of drug and materiel safety that had only been extrapolated from studies of men (e.g., chemical agent prophylaxis, fatigue countermeasures). Several important assumptions about female physiology and occupational risks were found to be astoundingly wrong. Hormonal changes through the menstrual cycle were less important to acute health risks and performance than predicted, exercise did not increase risk for amenorrhea and consequent bone mineral loss, and women tolerated G-forces and could be as safe as men in the cockpit if their equipment was designed for normal size and strength ranges. Data on personal readiness issues, such as body fat, physical fitness, nutrition, and postpartum return to duty, allowed reconsideration of standards that were gender appropriate and not simply disconnected adjustments to existing male standards. Other discoveries directly benefited men as well as women, including development of medical surveillance databases, identification of task strength demands jeopardizing safety and performance, and greater understanding of the effects of psychosocial stress on health and performance. This surge of research has translated into advances for the welfare of service women and the readiness of the entire force; relevant gender issues are now routine considerations for researchers and equipment developers, and some key remaining research gaps of special importance to military women continue to be investigated.

Pregnancy-related changes in physical activity, fitness, and strength

PURPOSE

The objective was to examine the pregnancy-related changes in physical activity, fitness, and strength in women of varying body mass indices (BMI).

METHODS

Women (N = 17 low BMI, N = 34 normal BMI, and N = 12 high BMI, mean age +/- SD = 30.7 +/- 4.1 yr) were studied before pregnancy (0 wk) and postpartum (6 and 27 wk) for body composition and for physical activity, fitness, and strength. Physical activity was assessed by questionnaire, fitness by a maximal oxygen consumption (VO2) test on a cycle ergometer, and strength by the one-repetition maximum test. Data were analyzed by repeated measures ANOVA testing for time and BMI group.

RESULTS

Total physical activity differed qualitatively, but not quantitatively, with time. Significant time effects were observed for maximal workload, heart rate, respiration rate, ventilation, VO2, respiratory exchange ratio, and strength. VO2max, adjusted for weight, dropped by approximately 385 mL x min(-1) from 0 to 6 wk postpartum (P < 0.0001) and by approximately 234 mL x min(-1) from 0 to 27 wk postpartum (P < 0.01). The high-BMI group had a lower VO2max (adjusted for weight or fat-free mass) than the normal-BMI group (P < 0.05). Strength decreased for the leg press by 24% (P < 0.02) and for the latissimus pull down by 8% (P < 0.01) from 0 to 6 wk postpartum, and then increased by 44 and 12%, respectively (both P < 0.05), by 27 wk postpartum.

CONCLUSION

Relative to prepregnancy performance, fitness and strength declined in the early postpartum period but improved by 27 wk postpartum.

Changes in basal metabolic rate during pregnancy in relation to changes in body weight and composition, cardiac output, insulin-like growth factor I, and thyroid hormones and in relation to fetal growth

BACKGROUND

The total energy cost of pregnancy is largely due to an elevated basal metabolic rate (BMR). Large variations in the BMR response to pregnancy have been reported, but the factors associated with this variability are incompletely known.

OBJECTIVE

The objective was to identify factors associated with variability in the BMR response to pregnancy.

DESIGN

In 22 healthy women, BMR, body weight (BW), total body fat (TBF), fat-free mass (FFM), circulatory variables, serum concentrations of insulin-like growth factor I (IGF-I), and thyroid hormones were measured before pregnancy and in gestational weeks 14 and 32. BMR and BW were also measured in gestational weeks 8, 20, and 35. Fetal weight was estimated in gestational week 31.

RESULTS

In gestational week 14, the increase in BMR correlated significantly with the corresponding increase in BW and with the prepregnancy percentage of TBF. Together these variables explained approximately 40% of the variability in the BMR response. In gestational week 32, the increase in BMR correlated significantly with the corresponding changes in BW, TBF, FFM, IGF-I, cardiac output, and free triiodothyronine. The increase in BW in combination with fetal weight or with the elevated concentration of IGF-I in serum explained approximately 60% of the variability in the increase in BMR.

CONCLUSIONS

Weight gain and the prepregnancy percentage of TBF-ie, factors related to the maternal nutritional situation-are important factors with regard to the variability in the BMR response to pregnancy. Thus, it is important to consider the nutritional situation before and during gestation when assessing pregnancy energy requirements.