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6 Anthropometry Paola Primatesta and Vasant Hirani
Obesity, a major risk factor for cardiovascular disease, diabetes, hypertension and premature death1,2,3,4,5 is increasing in the industrialised countries6,7 and is rapidly increasing worldwide.8 Poor diets together with sedentary lifestyles have been shown to be the main causes in the development of obesity.9,10 In the context of a survey on minority ethnic groups, the way obesity is assessed is of particular relevance, given the differences in body shape between the minority ethnic groups. A widely accepted measure of obesity is body mass index (BMI), a measurement which allows for differences in weight due to height, in accordance with the World Health Organisation (WHO) International Standards for the classification of obesity in adults.11 There is nevertheless a lack of evidence of the validity of this measure for an ethnically diverse population or evidence of a suitably applicable method for classification of specific groups in the population.12 BMI does not distinguish between mass due to body fat and mass due to muscular physique and does not take account of the distribution of fat. Therefore the use of this measure alone may not give an exhaustive picture of the minority ethnic groups in terms of their risk of chronic disease such as cardiovascular disease and diabetes. Informants who may not be defined as obese using BMI may still have a high degree of central obesity with the associated health risks.13 A measure of central obesity is waist-hip ratio (WHR). Central obesity has been generally recognised as a risk factor in relation to chronic diseases5,14 of which diabetes has a much higher prevalence amongst all minority ethnic groups than in the white population.15,16,17 The link between generalised obesity (as measured by BMI) and central obesity (as assessed by WHR) may be stronger in some minority ethnic groups than others (eg in Whites and Black Caribbeans than in South Asians), therefore both need to be investigated to assess minority ethnic group differences. Variations in body shape amongst different minority ethnic groups have been observed in a recent survey of minority ethnic groups.18 The findings suggested that Afro-Caribbean men and women were both taller and heavier than the Asians, though on average WHRs were lower. Other studies have provided data on distribution of body fat and obesity among ethnic minorities,19,20,21,22 but the findings were limited to specific groups (mainly Black Caribbeans and South Asians) and specific geographic areas. The 1999 Health Survey provides a large-scale representative sample to investigate differences between these and other minority ethnic groups and to look at subgroups of the South Asian population in England. The anthropometric measures presented in this chapter for adults (aged 16 and over) focus on measurements of height and weight, used to calculate body mass index (BMI); and of waist and hip, used to calculate waist-hip ratio (WHR). Methods and definitions are first presented. The distributions of these measurements in minority ethnic groups are then reported and the associations of socio-economic variables (social class of head of household and equivalised household income) with raised BMI, obesity and WHR are examined. 6.2 Methods and definitions of measurement Full details of the protocols for carrying out the measurements are contained in Volume 2, Appendix B and are briefly summarised here. Height and weight were measured by the interviewer and waist and hip circumferences by the nurse. Height Height was measured by interviewers, using a portable stadiometer with a sliding head plate, a base plate and three connecting rods marked with a metric measuring scale. Informants were asked to remove shoes. One measurement was taken, with the informant stretching to the maximum height and the head positioned in the Frankfort plane. The reading was recorded to the nearest millimetre. Weight Weight was measured by interviewers, using a Soehnle electronic scale with a digital display. Informants were asked to remove shoes and any bulky clothing. A single measurement was recorded to the nearest 100 g. Informants who were pregnant, chairbound, or unsteady on their feet were not weighed. Informants who weighed more than 130 kg were asked for their estimated weights because the scales are inaccurate above this level: these estimated weights were included in the analysis. In the analysis of height and weight, data from those who were considered by the interviewer to have unreliable measurements, for example those who had excessive clothing on, were excluded from the analysis. Body Mass Index (BMI) The Body Mass Index (BMI), defined as weight (kg)/height (m2), has been used to date in the Health Survey series. BMI was calculated for all informants for whom a valid height and weight measurement
was recorded. Adult informants were classified into the following BMI
groups:
Moreover, the obese category can be split further to identify those with morbid obesity (BMI greater than 40 kg/m2), a group at high risk of morbidity and mortality.23 Where the obese group was large enough this category was also analysed (see Section 6.3.3). Waist and hip Waist was defined as the midpoint between the lower rib and the upper margin of the iliac crest, and was measured by nurses using a tape with an insertion buckle at one end. Hip was defined as the widest circumference around the buttocks below the iliac crest. Both measurements were taken twice, using the same tape, and were recorded to the nearest even millimetre. Those whose two waist or hip measurements differed by more than 3 cm had a third measurement taken. The mean of the two valid measurements was used in the analysis. For waist and hip measurements all those who reported that they had a colostomy or ileostomy, or were chairbound or pregnant, were excluded from the measurement. All those with measurements considered unreliable by the nurse, for example due to excessive clothing or movement, were excluded from the analysis. Waist-hip ratio Waist-hip ratio (WHR) was defined as the waist circumference divided by the hip circumference (both in metres). WHR is a measure of deposition of abdominal fat (central obesity). Unlike BMI there is no consensus about appropriate WHR criterion levels.24 It has been suggested that cut-off points such as those in use in earlier surveys in this series may not be appropriate for use in all minority ethnic groups, because of variations in body shapes.25,26 However, there are as yet no accepted WHR cut-off points for minority ethnic groups, and for consistency the same cut-off values as in the 1994 and 1998 reports have been used: a raised WHR has been taken to be 0.95 or more in men and 0.85 or more in women. WHR was calculated for all informants for whom a valid waist and hip circumference measurement was recorded by the nurse who visited them. The response rates for these measurements are presented in Table 6.1. 6.3.1 Height Men were generally taller than women: this was true in all minority ethnic groups and in the general population. The mean observed height in men aged 16 and above ranged from 165.9 cm (Bangladeshi) to 174.2 cm (Black Caribbean). The mean height of men in the general population was 174.6 cm. After adjusting for age Bangladeshi, Chinese, Indian and Pakistani men were significantly shorter than their counterparts in the general population, whereas Black Caribbean and Irish men were about the same height as the general population. Mean observed height in women varied from 153.3 cm (in Bangladeshi women) to 162.8 cm (in Black Caribbean women). This latter group was taller than the general population, where the mean height was 161.1 cm. Age standardisation confirmed that Black Caribbean women were on average significantly taller than those in the general population, while all other groups (except for the Irish) were significantly shorter than their counterparts in the general population. Height decreased with age in both sexes and in all minority ethnic
groups. 6.3.2 Weight As in the general population, in all minority ethnic groups in both sexes weight increased from age 16-34 to age 35-54 and then decreased. The only exceptions were Black Caribbean women, where weight continued to increase in the oldest group, and Indian women, where it remained about the same. In general men were heavier than women. The observed mean weight in men of all minority ethnic groups was lower than in the general population: it varied from 65.5 kg among Bangladeshi men to 80.8 kg among Irish men, while the general population had a mean weight of 81.2 kg. After age adjustment this tendency was confirmed: men from all minority ethnic groups, with the exception of those of Black Caribbean origin, were significantly lighter than the general population. The variation in weight between minority ethnic groups was greater among women than among men. Women in the general population had a mean weight of 68.4 kg, while those of Bangladeshi origin were the lightest (56.6 kg) and those of Black Caribbean origin were the heaviest at 74.0 kg. These differences were reduced after age was adjusted for, but even after age standardisation women in all minority ethnic groups (with the exception of women of Black Caribbean and Irish origin) were significantly lighter than those in the general population. Consistently with findings reported elsewhere,18 Black Caribbeans, both men and women, were thus found to be, on average, taller and heavier than men and women of Asian origin. Men's BMI Mean observed BMI in men varied from 23.8 kg/m2 among Bangladeshis to 26.7 kg/m2 in the Irish. It was below 25 kg/m2 (the threshold for overweight) in Bangladeshi and Chinese men, at about the overweight threshold among Indian and Pakistani men and above the overweight threshold in Black Caribbean and Irish men, and in the general population. The observed prevalences of overweight and obesity reflected this pattern. Among Bangladeshis the prevalence of obesity was 5.4%, about half the prevalence among the other South Asian groups. Chinese men also showed a low prevalence of obesity, at 6.2%, while the Irish had the highest: a fifth of them (20.4%) were obese. These observed findings were confirmed after adjusting obesity prevalence for age. Age-adjusted obesity risk ratios showed levels of obesity to be about the same for Black Caribbean men (risk ratio 1.02) and Irish men (1.04) as for the general population, but lower for Pakistani men (0.74) and Indian men (0.66) and still lower for Chinese men (0.38) and Bangladeshi men (0.32). Bangladeshis were thus about three times less likely to be obese than the general population. They were also significantly less likely to be obese than Indian and Pakistani men. The observed prevalence of morbid obesity was less than 1% in men in all minority ethnic groups with the exception of Irish men (1.2%). (Data not shown.) Women's BMI Among women, obesity prevalence was high for Black Caribbean women (risk ratio
1.49) and Pakistani women (1.56), and low only for Bangladeshi (0.50)
and Chinese women (0.20).
In women the differences between the highest and the lowest rates (both observed
and standardised) were much larger than in men. Compared with women
in general, Black Caribbean and Pakistani women were more likely to
be obese (about 50% more likely), while Chinese and Bangladeshis were
much less likely to be obese: Bangladeshi women were only three-fifths
as likely as the general population to be obese, and Chinese women were
five times less likely than the general population to be obese. Compared with women in general, Black Caribbean women were twice as likely to have morbid obesity, but no difference was observed for Pakistani women, the other group with the highest obesity prevalence. (Data not shown.)
Comparison between the sexes In the general population, mean BMI for women was about the same as for men, but a higher proportion of women than men were obese (BMI>30 kg/m2). In some minority ethnic groups (Indian, Pakistani and, in particular, Black Caribbean) women had higher mean BMI than men. In the South Asian and Black Caribbean groups, the prevalence of obesity was higher among women than men, the difference between the sexes being much greater than in the general population. (It should be noted that these comparisons between the sexes are not age-standardised.) Variations in BMI by age group Patterns of variation in mean BMI and in obesity prevalence by age group varied between men and women. In men, observed mean BMI was lowest among those aged 16-34, peaked at age 35-54, then decreased in all minority ethnic groups with the exception of Irish men, among whom, as in the general population, it continued to increase with age. As in the general population, mean BMI increased with age in women of all minority ethnic groups, and was therefore highest among those aged 55 and over. The prevalence of obesity in men increased with age in the Irish, Indian and Chinese groups, while it peaked at 35-54 in all other minority ethnic groups and the general population. In women the prevalence of obesity increased with age, with the exception
of Bangladeshi and Chinese women, the latter showing relatively low
rates at all ages. The increase with age was particularly marked among
Black Caribbean and Indian women: obesity increased from 19.5% in the
16-34 age group to 51.9% in those aged 55 and over among Black Caribbean
women and from 9.2% to 35.8% among Indian women.
6.3.4 Waist-hip ratio Raised waist-hip ratio denotes a waist-hip ratio (WHR) of more than 0.95 for men or 0.85 for women, and is referred to below as central obesity (in contrast with general obesity, derived from BMI). Men's WHR In men, both observed mean WHR and the observed prevalence of raised WHR were highest among the Indian and Irish groups, and lowest among the Chinese group. More than a third (36.1%) of Indian men were centrally obese compared to less than a fifth of Chinese men (17.9%). After age standardisation, men in all South Asian groups were about half again as likely as the general population to be centrally obese. Their risk ratios for raised WHR were not very different from each other (Indian 1.48, Pakistani 1.54, Bangladeshi 1.33). Black Caribbean and Chinese men were less likely to show raised WHR (risk ratios 0.62 and 0.76) than either Asians or the general population. Irish men's raised WHR was not significantly different from that of the general population. Prevalence of raised WHR (men>0.95, women>0.85) Black General
Women's WHR Among women of all minority ethnic groups the observed prevalence
of raised WHR was higher than in the general population. In particular,
one third or more of Bangladeshi (42.8%), Pakistani (32.9%) and Black
Caribbean women (33.0%) showed raised WHR. After age standardisation,
women from all minority ethnic groups were more likely to be centrally
obese than women in general, risk ratios ranging from 1.37 for Irish
women to 3.63 for Bangladeshi women. Bangladeshi women were thus more
than three times as likely to be centrally obese as the general population. Comparison between the sexes Mean waist-hip ratio was higher in men than in women in all minority ethnic groups. Variations in WHR by age group Mean WHR and raised WHR increased with age in both sexes and in all minority
ethnic groups. Relationship between BMI and WHR BMI and WHR were highly correlated, in all minority ethnic groups and both sexes. However, the correlation coefficients were higher in men than in women and among women the correlation was higher among Black Caribbean than South Asian groups. (Data not shown.) The two indices showed different patterns of variation between minority ethnic groups. The prevalence of generalised obesity (BMI>30 k/gm2) was lower for South Asian and Chinese men than for Black Caribbean and Irish men, for both of whom it was at about the same level as in the general population. In contrast, the prevalence of central obesity, as assessed by raised WHR, was relatively high among South Asian men. Only Chinese men were low on both measures. Black Caribbean men had the same generalised obesity as the general population, but lower central obesity. Among women, the prevalence of generalised obesity was high for Black Caribbean women (risk ratio 1.49) and Pakistani women (1.56), and low only for Bangladeshi (0.50) and Chinese women (0.20). But women's levels of central obesity (raised WHR) in all six minority ethnic groups were well above that of the general population, with risk ratios from 1.37 for Irish women to 3.63 for Bangladeshi women. Of the South Asian groups, Pakistanis and Indians (both men and women) showed a higher prevalence of generalised obesity than Bangladeshis. For men, levels of central obesity were similar for all three groups, but Pakistani and Bangladeshi women had a higher prevalence of central obesity than Indian women. 6.4 Obesity, by socio-economic variables 6.4.1 Social class of head of household BMI In men the observed differences in BMI by social class of head of household were generally small in all minority ethnic groups. The largest difference was among Bangladeshis, where mean BMI was 22.8 kg/m2 in non-manual and 24.1 kg/m2 in manual social classes. As observed for mean BMI, the prevalence of obesity among Indians and Pakistanis was higher in men in non-manual (13.2% and 13.0% respectively) than manual social classes (10.5% and 11.8%) while in Black Caribbean, Bangladeshi and Chinese men the reverse was apparent; for example, among Black Caribbean men the prevalence of obesity was 17.2% in non-manual and 19.6% in manual classes; and among Chinese men it was 5.6% and 7.4% respectively. After standardisation no significant differences in the prevalence of obesity were seen between men of non-manual and manual social classes of the same minority ethnic group. Women showed more of a difference by social class than men, for both BMI and
obesity: in all minority ethnic groups the observed mean BMI and the
prevalence of obesity were higher in the manual than in the non-manual
social classes. The difference in the prevalence of obesity between
the non-manual and manual social classes was largest in Black Caribbean
women (25.8% in non-manual, 36.9% in manual classes) and Bangladeshi
women (3.1% and 11.5% respectively). After age standardisation the prevalence
of obesity was still higher in manual than in non-manual social classes
in most minority ethnic groups (for example, it was about 60% greater
in Black Caribbean women in the manual social classes and about 40%
greater in those in the non-manual social classes in comparison to the
general population) although the differences were only significant for
Bangladeshi women at the 95% significance level. Waist-hip ratio Both men and women of most minority ethnic groups had a higher prevalence of mean WHR in manual social classes than in non-manual social classes. A similar pattern was observed for raised WHR in almost all minority ethnic groups, with the exception of Indian men and Bangladeshi women where the reverse was true. The largest difference in the prevalence of raised WHR between manual and non-manual social classes was among Black Caribbean and Bangladeshi men where the increase was more than three times, from 6.7% to 25.2% in Black Caribbean and from 10.2% to 31.9% in Bangladeshi men. After age standardisation, the risk of raised WHR was higher in manual
social classes in both men and women, and the pattern remained generally
similar to the observed findings. The exceptions were among Indian,
Chinese and Irish men, where social class had no significant association
with the prevalence of raised WHR. 6.4.2 Equivalised household income BMI In men, mean observed BMI increased with income in all minority ethnic groups with the exception of Bangladeshis (but not in the general population) so that it was highest in the highest income tertile. The prevalence of obesity showed a less clear pattern, although for some groups, such as Black Caribbean men, there was a clear gradient, with prevalence increasing with income, from 9.8% in the lowest tertile to 23.4% in the highest tertile. After standardisation, the prevalence of obesity among men of Black Caribbean origin was still higher among men in the highest income tertile than among those in the lowest, but the differences were no longer significant. Among men in the other minority ethnic groups the differences were much smaller. For women, those in the lowest income tertile had the highest prevalence of
obesity. For example, the prevalence of obesity among Indian women more
than doubled from 18.0% in the highest income tertile to 37.4% in the
lowest income tertile. However, this pattern was partly explained by
the different age distribution in the groups: after age standardisation,
most minority ethnic groups showed smaller differences by income tertiles. Waist-hip ratio In men there was no clear pattern in mean observed WHR by income. The prevalence of raised WHR was generally higher in men in the lowest income tertile than in those in the highest. After age standardisation, an inverse gradient in raised WHR was apparent, with men in the lowest income tertile at highest risk. Among women an inverse association with income was shown in both observed
mean and raised WHR, so that generally the prevalence of raised WHR
was higher in women in the lowest income tertile than in those in the
highest. Age standardisation generally confirmed the observed findings.
References and notes 1 Pi-Sunyer FX. The medical hazards of obesity. Ann Intern Med 1993; 119:655-660. 2 Franz MJ. Managing obesity in patients with comorbidities. J Am Diet Assoc 1998; 98 Suppl 2:S39-S43. 3 Effective Health Care. The prevention and treatment of obesity. NHS Centre for Reviews and Dissemination, University of York. Churchill Livingstone 1997; 3:2. 4 Gensini GF, Comeglio M, Colella A. Classical risk factors and emerging elements in the risk profile for coronary artery disease. Eur Heart J 1998; 19 Suppl A:A53-61. 5 Pi-Sunyer FX. Health implications of obesity. Am J Clin Nutr 1991; 53 Suppl 6:1595S-1603S. 6 Seidell JC. Obesity in Europe: scaling an epidemic. Int J Obes 1995; 19 Suppl 3:S1-S4. 7 Primatesta P et al. Risk factors for cardiovascular disease. Chapter 3 in Erens B, Primatesta P (eds) Health Survey for England 1998, The Stationery Office, London, 1999. 8 World Health Organisation. Obesity: preventing and managing the global epidemic. Report of a WHO consultation, Geneva, 3-5 Jun 1997. Geneva: WHO, 1998. (WHO/NUT/98.1.) 9 Prentice AM, Jebb SA. Obesity in Britain: gluttony or sloth? BMJ 1995; 311(7002):437-9. 10 James WP. A public health approach to the problem of obesity. Int J Obes Relat Metab Disord 1995; 19:S37-45. 11 World Health Organisation. Measuring Obesity. Classification and description of anthropometric data. Report on a WHO consultation on the epidemiology of obesity. Copenhagen, Denmark: WHO Regional Office for Europe, Nutrition Unit; 1988. 12 Report of a WHO Expert Committee. Physical Status: The use and interpretation of Anthropometry. WHO Technical Report Series, No.854. 1985. 13 Allied Dunbar, Health Education Authority, Sports Council. Allied Dunbar National Fitness Survey: A report on activity patterns and fitness levels. Main findings. (p.74) Sports Council, Health Education Authority, London, 1992. 14 Kannel WB, Cupples LA, Ramaswami R, Stokes J, Kregor BE, Higgins M. Regional obesity and risk of cardiovascular disease; the Framingham Study. J Clin Epidemiol 1991; 44:183-190. 15 Stevens A, Raftery J. Health care needs assessment. Radcliffe Medical Press, Oxford, 1994, Vol.1, p.48. 16 Kissebah AH, Vydelingum N, Murray R, Evans DJ, Hartz AJ, Kalkhoff RK, et al. Relation of body fat distribution to metabolic complications of obesity. J Clin Endocrinol Metab 1982; 54:254-60. 17 McKeigue PM, Shah B, Marmot MG. Relation of central obesity and insulin resistance with high diabetes prevalence and cardiovascular risk in south Asians. Lancet 1991; 337:382-6. 18 Black and minority ethnic groups in England: the second health & lifestyles survey. Health Education Authority, London, 2000. 19 Wang J, Thornton JC, Russell M, Burastero S, Heymsfield S, Pierson RN Jr. Asians have lower body mass index (BMI) but higher percent body fat than do whites: comparisons of anthropometric measurements. Am J Clin Nutr 1994; 60:23-8. 20 Dhawan J, Bray CL, Warburton R, Ghambhir DS, Morris J. Insulin resistance, high prevalence of diabetes, and cardiovascular risk in immigrant Asians. Genetic or environmental effect? Br Heart J 1994; 72:413-21. 21 McKeigue PM, Marmot MG, Adelstein AM. Diet and risk factors for coronary artery disease in Asians in north-west London. Lancet 1985; 2:1060-90. 22 Miller GJ, Kotecha S, Wilkinson WH, et al. Dietary and other characteristics relevant for coronary heart disease in men of Indian, West Indian and European descent in London. Atherosclerosis 1988; 70:63-72. 23 NHS Consensus Development Conference. Gastrointestinal surgery for severe obesity. Nutrition 1996; 12:397-402. 24 Molarius A, Seidell JC. Selection of anthropometric indicators for classification of abdominal fatness - a critical review. Int J Obes 1998; 22:719-727. 25 Croft JB, Keenan NL, Sheridan DP, Wheeler FC, Speers MA. Waist-to hip ratio in a biracial population: measurement, implications, and cautions for using guidelines to define high risk for cardiovascular disease. Am Diet Assoc 1995; 95:60-64. 26 C Bouchard, GA Bray, and VS Hubbard.
Basic and clinical aspects of regional fat distribution. Am J
Clin Nutr 1990; 52:946-950. 6.1 Response to anthropometric measurements, by minority ethnic group 6.2 Height, by minority ethnic group 6.3 Height, by age within minority ethnic group 6.4 Weight, by minority ethnic group 6.5 Weight, by age within minority ethnic group 6.6 Body mass index (BMI), by minority ethnic group 6.7 Body mass index (BMI), by age within minority ethnic group 6.8 Body mass index (BMI), by social class of head of household within minority ethnic group 6.9 Body mass index (BMI), by equivalised household income tertile within minority ethnic group 6.10 Waist-hip ratio (WHR), by minority ethnic group 6.11 Waist-hip ratio (WHR), by age within minority ethnic group 6.12 Waist-hip ratio (WHR), by social class of head of household within minority ethnic group 6.13 Waist-hip ratio (WHR), by equivalised household income tertile within minority ethnic group
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