George T. H. Ellison

Inter- and intraindividual variation in daily energy expenditure of the pouched mouse (Saccostomus campestris)

1. We measured the simultaneous energy expenditure of five male and six female pouched mice (Saccostomus campestris), over 3 consecutive days, using the doubly labelled water (DLW) technique. The aim was to assess the interindividual scaling of daily energy demands and also the repeatability of measures of daily energy expenditure when using doubly labelled water. 2. Individual mice were housed in cages, given free access to food and water and were kept in a natural photoperiod (February at 26°S) at a mean temperature of 26.5°C (daily range 25-28°C). 3. Males were significantly heavier than the females, as is typical in this species. Mean energy expenditure (Watts) (single-pool model) over 3 days, across individuals, was positively related to body mass (reduced major axis scaling exponent b = 1.96) and to change in body mass over the 3 days

Do the psychosocial and behavioral changes that accompany motherhood influence the impact of pregnancy on long-term weight gain ?

The aim of the present study was to assess whether the psychosocial and behavioral changes that occur during and after pregnancy influence long-term weight gain. The study examined 74 mothers enrolled in the Antenatal Care (ANC) Project (a randomized controlled trial of antenatal care based in South London), all of whom had volunteered to take part in a subsequent follow-up study. Data on body weight at the beginning of pregnancy; lifestyle and behavior during pregnancy; antenatal care and obstetric history; together with measures of postnatal depression and parenting stress following pregnancy were taken from the existing ANC Project database. Additional measurements of height and weight together with information on a variety of lifestyle changes and psychosocial characteristics, were gathered during semi-structured interviews at each mothers home, two and a half years after their children had been born. The results show that pregnancy-related weight gains are not simply the result of retaining weight that is gained during pregnancy, but that they also originate from gaining additional weight in the postpartum period. Mothers who felt they ate more after their children were born, had significantly greater long-term weight gains (2.78 (1.42) kg) than those who felt that they had not increased their food intake (-1.15 (0.76) kg; t = 2.49, p = 0.016). Similarly, mothers who felt they had greater access to food postpartum, had significantly greater long-term weight gains (1.70 (0.87) kg) than those who felt they did not have greater access to food (-1.37 (1.13) kg; t = 2.18, p = 0.032). There was some evidence that the lifestyle changes which accompany pregnancy and motherhood increase some womens vulnerability to eating disorder psychopathology. Mothers who felt they did less exercise after pregnancy than they did before, were also at greater risk of long-term weight gain (p = 0.028), as were mothers with low numbers of supportive individuals (p = 0.033). Neither the stress of parenting nor maternal depression were significantly associated with an increased risk of long-term weight gain (p > 0.05).

The impact of pregnancy on the long-term weight gain of primiparous women in England

OBJECTIVES: To investigate the impact of pregnancy on long-term weight gain of primiparous mothers in England, and to identify potential risk factors for maternal obesity. DESIGN: A retrospective, repeat-pregnancy study which examined the change in maternal body weight from the beginning of the first successful pregnancy to the beginning of the second. SUBJECTS: Two hundred and forty-three mothers, all of whom had been weighed during the first trimester of their first and second pregnancies, and none of whom had fallen pregnant less than 12 months after the birth of their first child. MEASUREMENTS: Sociodemographic, behavioural, medical, obstetric and perinatal data, together with antenatal measurements of maternal body weight and height, were extracted from each mother’s obstetric notes. A comprehensive survey of weighing scales used at all antenatal clinics was undertaken. RESULTS: After accounting for the effect of ageing, there was no significant long-term increase in mean maternal body weight following the first pregnancy (95% Confidence Intervals: −0.82–0.28 kg). While most mothers (70.8%) gained 1.0 kg or less, 24.7% gained more than 1.54 kg. Even after accounting for the maximum error in clinic scales, 14.8% of the mothers gained 1.54 kg or more in association with their first pregnancy. Mothers with higher BMIs at the beginning of their first pregnancy, who gained more weight during pregnancy, gave birth to heavier babies and had longer intervals between their pregnancies, gained significantly more weight from one pregnancy to the next. CONCLUSIONS: Pregnancy has little impact on the mean weight gain of primiparous women from England, who have a low prevalence of obesity (BMI≥26.0, 25.5%). Nevertheless, pregnancy may be associated with a permanent increase in maternal body weight simply because it is a period of positive energy balance during which some women gain excessive weight. Other factors, such as prepregnant BMI, determine whether long-term weight gain actually occurs.

The standardization of race and ethnicity in biomedical science editorials and UK biobanks

As the search for human genetic variation has become a priority for biomedical science, debates have resurfaced about the use of race and ethnicity as scientific classifications. In this paper we consider the relationship between race, ethnicity and genetics, using insights from science and technology studies (STS) about processes of classification and standardization. We examine how leading biomedical science journals attempted to standardize the classifications of race and ethnicity, and analyse how a sample of UK genetic scientists used the concepts in their research. Our content analysis of 11 editorials and related guidelines reveals variations in the guidance on offer, and it appears that there has been a shift from defining the concepts to prescribing methodological processes for classification. In qualitative interviews with 17 scientists, the majority reported that they had adopted socio-political classification schemes from state bureaucracy (for example, the UK Census) for practical reasons, although some scientists used alternative classifications that they justified on apparently methodological grounds. The different responses evident in the editorials and interviews can be understood as reflecting the balance of flexibility and stability that motivate standardization processes. We argue that, although a genetic concept of race and ethnicity is unlikely to wholly supplant a socio-political one, the adoption of census classifications into biomedical research is an alignment of state bureaucracy and science that could have significant consequences.

Is there an independent association between parity and maternal weight gain

The independent associations between parity and maternal body mass index (BMI), and between parity and maternal weight gain, were investigated using a combination of cross-sectional and longitudinal analyses based on a retrospective, repeat-pregnancy study that examined the change in maternal body weight from the beginning of one pregnancy to the beginning of the next. A group of 523 multiparous women who had been weighed regularly during pregnancy, and none of whom had fallen pregnant less than 12 months after the birth of their previous child, were examined. Sociodemographic, behavioural, medical, obstetric and perinatal data, together with antenatal measurements of maternal body weight and height, were abstracted from each mothers obstetric notes. Parity was found to be independently associated with maternal BMI (p < 0.001), gestational weight gain (p < 0.001) and interpregnancy weight gain (p = 0.032). Women of different parities were found to be at differential risk of long-term weight gain for two reasons. First, primiparous women are at risk of long-term weight gain because they gain the most weight during pregnancy, and high gestational weight gain is in itself a risk factor for long-term weight gain. Second, women of higher parity (4+) are at risk of long-term weight gain because they gain more weight in association with pregnancy, irrespective of the amount of weight they gain during their pregnancies. For women of parity 3 or less, the association between maternal body weight and parity appears to be the result of cumulative weight gained during successive pregnancies. For women of greater parity, the association between maternal body weight and parity is partly the result of cumulative excess gestational weight gained during successive pregnancies, and partly the result of gaining more weight from the beginning of one pregnancy to the next at later pregnancies.

Practical Approaches for Estimating Prepregnant Body Weight

Measurements of prepregnant body weight have important research and clinical applications. In practice, however, they are not always recorded; even when they are, this information is not always readily available. For this reason, researchers and clinicians have to rely on retrospective estimates of prepregnant weight, which can be estimated using: 1) maternal self-reports, 2) retrospective extrapolation, or 3) standardized estimates that correct for weight gained during early pregnancy. The aim of the present study was to examine the relative merits of these three approaches. Maternal self-reports tend to be unreliable and biased, being influenced by a variety of sociodemographic characteristics that generally underestimate true prepregnant body weight. Estimates of prepregnant weight based on retrospective extrapolation are vulnerable to measurement error, transient fluctuations in body weight, and incorrectly assume that the rate of weight gain is constant throughout pregnancy. Standardized estimates that correct for weight gained during early pregnancy incorrectly presume that there is little interindividual variation in gestational weight gain and that weight gain is similar for each woman in consecutive pregnancies. Because none of these techniques can provide a precise measure of prepregnant weight, researchers have little alternative but to recruit and weigh women before they become pregnant, although measurements of body weight recorded during the first trimester of pregnancy may provide a reasonable indication of prepregnant weight. For clinicians, self-reports of prepregnant weight or measurements recorded early in pregnancy are probably sufficiently accurate for practical purposes whenever recent, accurate measurements of prepregnant weight are unavailable.

‘Population profiling’ and public health risk: When and how should we use race/ethnicity?

The limited reliability of race/ethnicity and the sensitivity surrounding its use to stereotype, discriminate and rationalize difference suggest it should not be used in population profiling for public health risk. However, race/ethnicity is crucial for assessing the risk of discrimination along the lines of race/ethnicity, and it can be the best available proxy for important unmeasured variables. Nonetheless, generating any data disaggregated by race/ethnicity can fuel the use of biological reductionism or cultural essentialism to explain inequalities in health. To maximize the benefits and minimize the disadvantages of using race/ethnicity this commentary suggests that: (1) race/ethnicity should primarily be used to assess the risk and impact of discrimination; (2) race/ethnicity should only be used as a proxy for variables that cannot be measured and when it is the most reliable proxy available; and (3) the use of race/ethnicity may be desensitized by emphasizing how categorization and discrimination are ultimately responsible for the utility of race/ethnicity as a proxy for related variables. These suggestions accept that race/ethnicity will continue to be used in population profiling, but that its use could be refined and reframed. To this end, the commentary explores the dilemma faced by the South African National Blood Service (SANBS), which was criticized for using race/ethnicity to identify blood donors at increased risk of undetectable HIV infection. While race/ethnicity might not have been the only reliable proxy for undetectable HIV infection, its use might have been more palatable had the SANBS explained how the utility of race/ethnicity reflected the legacy of apartheid and its enduring impact on the differential spread of HIV.

Principles for research on ethnicity and health: the Leeds Consensus Statement.

Background: There is substantial evidence that health and health-care experiences vary along ethnic lines and the need to understand and tackle ethnic health inequalities has repeatedly been highlighted. Research into ethnicity and health raises ethical, theoretical and methodological issues and, as the volume of research in this area grows, so too do concerns regarding its scientific rigour and reporting, and its contribution to reducing inequalities. Guidance may be helpful in encouraging researchers to adopt standard practices in the design, conduct and reporting of research. However, past efforts at introducing such guidance have had limited impact on research practice, and the diversity of disciplinary perspectives on the key challenges and solutions may undermine attempts to derive and promote guiding principles. Methods: A consensus building Delphi exercise—the first of its kind in this area of research practice—was undertaken with leading academics, practitioners and policymakers from a broad range of disciplinary backgrounds to assess whether consensus on key principles could be achieved. Results: Ten key principles for conducting research on ethnicity and health emerged, covering: the aims of research in this field; how such research should be framed and focused; key design-related considerations; and the direction of future research. Despite some areas of dispute, participants were united by a common concern that the generation and application of research evidence should contribute to better health-care experiences and health outcomes for minority ethnic people. Conclusion: The principles provide a strong foundation to guide future ethnicity-related research and build a broader international consensus.

Racial Categories in Medicine: A Failure of Evidence-Based Practice?

Race and ethnicity are imprecise markers of the genotypic and sociocultural determinants of health, argue the authors.

Climatic adaptation of body size among pouched mice (Saccostomus campestris: Cricetidae) in the southern African subregion

Morphological variation was studied among 209 pouched mice (Saccostomus campestris, Peters, 1846) from 104 localities in the southern African subregion. Climatic variables for these localities were generated using a climatic surface model developed with data from existing meteorological stations. These estimates of temperature, rainfall and seasonal variability were strongly correlated with latitude, so that the different climatic factors covaried. External measurements (body, tail and ear length) and body mass were strongly correlated with condylo-basal skull length which was taken as a more reliable measure of body size. Geographical variation in body size was significantly correlated with latitude, temperature and seasonality although these correlations appeared to be largely the result of a positive relationship between size and rainfall. In contrast, emperature apparently had little effect on morphology as there were no clear correlations between temperature and the size of appendages (tail or ear length). Rainfall might be more important than ambient temperature as a factor influencing body size in small fossorial and semi-fossorial mammals which spend most of their lives in warm subterranean microhabitats. Meanwhile, the smaller body size of pouched mice from localities with lower rainfall may represent anadaptation to reduce total energy requirements in arid and semi-arid areas where primary production and food availability is low.