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Biomedical subjects

N G Norgan

Publications and source records attributed to N G Norgan.

At least 19 recordsLinked to original sources
PubMed2005

Laboratory and field measurements of body composition.

OBJECTIVE: This background paper was prepared in response to a request to review the concepts related to measurement of body composition, to discuss laboratory and field methods of assessing body composition and to discuss the practical applications of the methods--how they might be used singly or in combination to provide data for a selected population. DESIGN: The common laboratory and field methods are described and discussed, with particular attention to the assumptions involved and the applicability of the methods to the different population groups. Most measurements of body composition are made in the field, at the bedside or clinic as opposed to in the laboratory. The laboratory methods have a role to play in their own right, in research into new concepts, models and methods. However, they are particularly important in establishing the accuracy of the field methods. SETTING: Field, bedside and laboratory studies. SUBJECTS: Children, adults, the elderly, ethnic groups. RESULTS: Laboratory estimates of body compositions are best performed by multi-component methods or by 2-component methods adjusted for to the populations under investigation. There is a scarcity of data for most of the populations in the world. CONCLUSIONS: Energy requirements based on body weight are an approximation since they do not take into account differences in body composition, which will better determine the true requirements. The measurement of body composition occurs in many branches of biology and medicine. It is used in the assessment of nutritional and growth status and in disease states and their treatment. Energy stores, skeletal muscle and protein content can be determined and changes monitored. In human energetics, body composition is widely used for the standardisation of other variables, such as basal metabolic rate (BMR), in the assessments of ethnic and environmental differences and of variability and adaptation to different levels of nutrition. Choosing a method is very problematic. Users want simple, inexpensive, rapid, safe accurate methods to measure body composition but speed and simplicity come at the expense of accuracy. Recommendations are made for age, sex, and in some cases, fatness and ethnic specific methods.

Adaptation, Physiological↗
PubMed2000

Long-term physiological and economic consequences of growth retardation in children and adolescents.

The application of a lifespan perspective in human biology in recent years has shown that a number of early environmental factors influencing human growth and development have long-term biological or psycho-social consequences. Human growth is characterized by prolonged infancy, an extended childhood phase and high rates of growth during the adolescent growth spurt. It is unlikely that these characteristics would have evolved without having advantages, and curtailments have the potential for disadvantage. The present paper examines the evidence for long-term physiological and economic consequences of growth retardation in children and adolescents. The emphasis is the biological and economic imperatives of survival, subsistence, reproduction and production rather than aspects of metabolic competence. Many of the consequences of growth retardation are determined by the direct effect on body size, but many other consequences arise from the conditions that cause the growth retardation. Catch up of retarded growth can occur, but does not usually do so because of the continued presence of the retarding agents. Basal metabolism and physical work capacity are usually commensurate with the size of the individual; mechanical efficiency of physical work is unchanged, but falls in activity levels may occur along with a reduction in the pace of activity. Growth retardation in childhood is associated with a higher disease and mortality risk in adulthood, with decreased productivity and employment and promotion prospects. Studies are showing that relative deprivation and the accumulation of socially patterned exposures are important in some societies. Height and growth retardation have proved invaluable in reflecting these factors, but the next generation of studies may require more discriminating indices.

Adolescent↗
PubMed2000

The accuracy of body weight and height recall in middle-aged men.

OBJECTIVE: To determine the accuracy of recalled height and weight, and calculated body mass index (BMI), over a 27-37 y period. DESIGN: Comparison of measured height and weight with recalled height and weight 27-37 y later. PARTICIPANTS: Two hundred and twenty-five men measured aged 18-24 y as physical education students at Loughborough Training College, UK, between 1958 and 1967. RESULTS: Initial body weights were over-estimated by 3.1 +/- 4.5 kg and heights by 1.1 +/- 1.8 cm, on average. Some 42% (95) of recalls were within 2.5 kg and 79% (178) within 2.5 cm, resulting in 58% (130) of the differences in BMI calculated from recalled and actual heights and weights to be within 1 kg/m2. However, 29% (66) of recalls were more than 5 kg and 8% (19) more than 10 kg from the measured values. Weight errors (actual-recalled) were negatively related (r = -0.43, P < 0.001) to weight gain over the 27-37 y interval. CONCLUSIONS: Middle-aged men who were formerly physical education students recalled their previous height and weight well, in most cases, 27-37 y later. The bias from recalled data would be to underestimate weight gain by 3 kg and BMI by 1 kg/m2, on average. Errors of more than 5 kg in 29% of participants and of more than 10 kg in 8% would be expected to interfere seriously with attempts to show epidemiological relations between early weight based on recall and subsequent outcomes.

Bias↗
PubMed1997

The beneficial effects of body fat and adipose tissue in humans.

Body fat and adipose tissue are considered to have beneficial effects when they promote or protect the present and future function. These effects do not occur at absolute amounts or percentages of the body weight but rather they are context specific. Body fat stores are the major energy stores of the body and are important determinants of survival in starvation or undernutrition. Reproduction features highly as a biological function. Humans are alone in having major sex-specific fat stores and patterns of fat distribution and these have been linked with the onset and maintenance of menstruation, with mate selection and sexual signalling, and with favourable pregnancy and lactation outcomes. To survive and reproduce good physical and psychological health are advantageous attributes. Work metabolism, bone health and, possibly immune function and energy balance itself, are related in functionally beneficial ways to fat content and distribution.

Adipose Tissue↗
PubMed1995

Evaluation of near infra-red interactance for assessment of subcutaneous and total body fat.

OBJECTIVE: Near infra-red interactance (NIRI) has been used for assessment of total body fatness, but its relationship with composition at the measurement site is not clear. This study examines the relationship of interactance with subcutaneous adipose tissue and muscle thickness as well as total body fat content. DESIGN: (i) Validation of NIRI by comparison with subcutaneous tissue thicknesses from ultrasound. (ii) Cross-validation of techniques for estimation of body fat content. SETTING: Laboratory. SUBJECTS: (i) 54 young adults (27 male and 27 female) and (ii) 63 middle-aged men. INTERVENTIONS: Measurements of subcutaneous adipose tissue thickness and muscle thickness using ultrasound, near infra-red interactance (Futrex 5000) and skinfold thicknesses were made at five sites in young adults. In middle-aged men total body fat was assessed by densitometry, NIRI and skinfold thickness. Measurements were made in duplicate by a single trained observer. RESULTS: Interactance measurements were related to subcutaneous adipose tissue thickness, although the relationship varied according to measurement site r = 0.09 at anterior thigh to 0.78 at biceps; P = 0.31 to < 0.0001). Muscle thickness explained additional variance in interactance only at biceps in women. Subcutaneous adipose tissue thickness correlated better with skinfold thickness (r = 0.56 to 0.92; P = 0.002 to < 0.0001) than with interactance. Mean difference in fat mass from densitometry +/- 95% limits of agreement was -1.61 +/- 7.68 kg for NIRI and -2.84 +/- 6.56 kg for skinfold thickness in middle-aged men. NIRI tended to underestimate higher (and overestimate lower) levels of fatness. CONCLUSIONS: NIRI performed no better than skinfolds in assessment of either subcutaneous or total body fat.

Adipose Tissue↗
PubMed1995

The effect of standardising the body mass index for relative sitting height.

The body mass index (BMI) has become a universal index of energy nutritional status in adults even though it is influenced by many factors other than energy stores. One of these is variation in height caused by variation in the length of the trunk and legs. Such variations occur between and within populations. In the British population, with a sitting height/stature (SH@S) ratio at the mode of population values, adjustment of BMI for SH/S ratio caused BMI to change by 1 kg/m2 or more in 33% of women and 10% of men and by 2 kg/m2 in 5% of women and 1% of men. The possible effects of shape, as evinced by SH/S ratios should be borne in mind when describing individuals or populations as overweight or obese in epidemiological studies and in decisions of clinical management.

Adult↗
PubMed1994

Interpretation of low body mass indices: Australian aborigines.

Low body mass index (BMI, kg/m2) has been proposed as a practical measure of energy undernutrition although it has some well-known limitations. Some reports have suggested that those Australian Aborigines living a largely traditional way of life have low BMI without compromised health status and may have paradoxically high levels of subcutaneous adipose tissue. The evidence for low BMI in Australian Aborigines is reviewed from the mean data of 1,174 individuals in 26 groups of adults and from the individual data of 349 of these individuals, collected before 1970. Three of the nine groups of women had mean BMI less than 18.5 kg/m2 and 4% of the individual men and 14% of the individual women had values less than 16 kg/m2, a value regarded as indicating severe chronic energy deficiency. Skinfold thicknesses were greater than expected from the BMI, suggesting paradoxically high subcutaneous fatness. The contribution of long-leggedness to low BMI was estimated from the regression of BMI on the sitting height to stature ratio (SH/S). For the 26 groups, this was estimated to be 2 kg/m2, r2 = 31%. The relationship was weaker with the individual data, r2 = 15%. Body shape as evinced by low SH/S does contribute to low BMI in these Australian Aborigines. Single cut-offs of BMI are not applicable to all population groups and allowance may have to be made for body form when using BMI to assess nutritional status.

Adolescent↗
PubMed1994

The influence of a 1-year programme of brisk walking on endurance fitness and body composition in previously sedentary men aged 42-59 years.

This study examined the influence of a 1-year brisk walking programme on endurance fitness and the amount and distribution of body fat in a group of formerly sedentary men. Seventy-two males, aged 42-59 years, body mass index 25.2 (0.3) kg.m-2 [mean (SEM)], were randomly allocated to either a walking group (n = 48) or control group (n = 24). Brisk walking speed was evaluated using a 1.6-km track walk. Changes in endurance fitness were assessed by measuring blood lactate concentration and heart rate during submaximal treadmill walking. Body composition was determined by hydrostatic weighing and anthropometry; energy intake was assessed from 7-day weighed food inventories. Differences in the response of walkers and controls were examined using two-way analyses of variance. Forty-two walkers (87.5%) completed the study and averaged 27.9 (1.4%) min.day-1 of brisk walking (range 11-46). Brisk walking speed averaged 1.95 (0.03) m.s-1 and elicited approximately 68 (1) % of maximum heart rate. Heart rate and blood lactate concentration during submaximal treadmill walking were significantly reduced in the walkers after 3, 6 and 12 months and the oxygen uptake at a reference blood lactate concentration of 2 mmol.l-1 was increased by 3.2 ml.kg-1.min-1 (14.9%) in the walkers at 6 months (P < 0.01). Although skinfold thicknesses at anterior thigh and medial calf sites decreased significantly for the walkers, the response of the two groups did not differ significantly for other body composition variables or for energy intake.

Adult↗
PubMed1994

Population differences in body composition in relation to the body mass index.

This paper examines the relationships between body mass index (BMI) and body composition in different population groups where low BMIs might be expected to occur and assesses the extent to which BMIs are influenced by size and shape. The relationship between BMI and fat as a percentage of body weight is approximately linear although theoretically a curvilinear relationship is to be expected. However, by allowing for a variable composition of weight differences, an approximately linear theoretical relationship is obtained. There are few direct data (e.g. from densitometry, hydrometry etc.) on body composition in the groups in question and to examine the relationships indirect data were used. The regression coefficients of fat-free mass on BMI for 285 samples of Africans, people of Asian origin, Indo-Mediterraneans and Pacific people were not significantly different in the various groups of each sex; % fat on BMI was similarly related in four groups of women. Intercept terms were all significantly different. Using the sitting height-to-stature ratio (SH/S) as an index of body shape in 158 groups, the regression coefficient of BMI on SH/S was 0.90 kg/m2 per 0.01 SH/S. Mean SH/S lies between 0.50 and 0.55 in most populations so that shape could affect BMI by 5 kg/m2 and influence markedly the interpretation of BMI. However, allowing for SH/S is not straightforward as there is as much variation within as between groups. In conclusion, low BMI approximates to low weight, fat mass and fat-free mass. There are differences in the relationships of BMI to body composition but over the range 20-25 kg/m2 these may not be important in epidemiological studies. To interpret BMI in terms of body composition in more detail it is necessary to take into account sex, age, shape and ethnicity.

Adipose Tissue↗
PubMed1994

The value of arm circumference measurements in assessing chronic energy deficiency in Third World adults.

OBJECTIVE: To assess the usefulness of mid-upper arm circumference (MUAC) as a substitute for body mass index (BMI: kg/m2) or an additional measure of adult nutritional state. DESIGN: Variously sampled adults aged 18-60 years from selected regions of five African countries, India, China and Papua New Guinea were measured. SUBJECTS: 2421 men and 3248 women were measured for their heights, weights and MUAC. Of these, 1569 men and 1905 women also had their triceps skinfold thickness measured, thus allowing additional estimates of muscle area circumferences and fat areas in the arm. RESULTS: MUAC and BMI were highly correlated in each national group; each group's MUAC differed from the overall mean MUAC at any BMI value by < 10%. Women's MUACs were smaller than men's at equivalent BMIs. Increases in MUAC with age were statistically significant but trivial. Muscle and fat measurements showed similar increases with BMI; a larger muscle mass in men explained their greater MUACs but muscle differences alone did not explain national variations in MUAC. The -1 SD MUAC value, taken as an independent measure of peripheral tissue wasting, readily distinguished those with a BMI < 16.0 from those with a BMI > 18.5; intermediate grades of BMI were poorly specified by MUAC values. CONCLUSION: MUAC values of 23.0 cm in men and 22.0 cm in women are useful cut-off points for simple screening of nutritional state. In combination with BMI it may provide a more refined classification of CED. This new combined classification scheme may be a better means of discriminating the at-risk underweight adults from those who are thin but not at risk.

Adolescent↗
PubMed1993

Brisk walking and serum lipoprotein variables in formerly sedentary men aged 42-59 years.

1. The purpose of this study was to examine the influence of brisk walking on serum lipoprotein variables. 2. Seventy-two apparently healthy but physically inactive men (aged 42-59 years) were recruited. These men were normotensive non-smokers without a history of dyslipidaemia. Subjects were randomly allocated on a 2 to 1 basis into either a walking group (n = 48) or a control group (n = 24). Walkers followed a self-monitored programme of brisk walking for 1 year, whereas control subjects maintained their habitual lifestyle. 3. Treadmill walking tests were conducted to examine changes in fitness. Concentrations of serum lipids and lipoproteins were determined in fasting subjects. The amount of body fat was measured by body density. Circumferences at the waist and hip and skinfold thicknesses were used to determine the distribution of body fat. Dietary intakes were assessed by weighed food inventories. 4. Seven subjects (six walkers and one control subject) dropped out during the study. Walkers did an average of 28 (SEM 1.4; n = 42) min of brisk walking/day. This improved endurance fitness but did not influence serum concentrations of total cholesterol, high-density lipoprotein cholesterol, triacylglycerol, apolipoprotein A-1, apolipoprotein B or lipoprotein (a). Neither body mass nor the amount of body fat changed, relative to control subjects. 5. These data suggest that brisk walking does not modify lipoprotein metabolism in normolipidaemic middle-aged men.

Adult↗
PubMed1992

Brisk walking improves endurance fitness without changing body fatness in previously sedentary women.

The purpose of this study was to examine the influence of brisk walking on endurance fitness and the amount and distribution of body fat in previously sedentary women. Twenty eight women [mean age (SEM): 44.9 (1.5) years] followed the walking programme for 1 year, whilst 16 acted as controls [age 44.4 (2.3) years]. Changes in endurance fitness were evaluated by measuring the oxygen uptake (VO2) at a reference blood lactate concentration of 2 mmol.l-1. Two 1.61-km field tests of walking were completed, one at maximal speed and one at a "brisk" speed, as well as a 1.61-km walk on a motorised treadmill. The amount and distribution of body fat was determined by hydrostatic weighing and anthropometry and energy intake was evaluated using the 7-day weighed food intake method. Walkers completed an average of 157 min.week-1 of brisk walking over the year. The following were increased in walkers, relative to controls: brisk walking speed [walkers 1.73 (0.05) m.s-1 vs 1.88 (0.07) m.s-1; controls 1.69 (0.05) m.s-1 vs 1.70 (0.05) m.s-1 at baseline and 12 months respectively, P < 0.01], maximal walking speed and VO2 at 2 mmol.l-1. In addition, brisk walking reduced heart rate and blood lactate concentration during stepping as well as during standard, submaximal treadmill walking. It did not modify either the amount or the distribution of body fat, despite an unchanged energy intake.

Adipose Tissue↗
PubMed1992

Maternal body composition: methods for measuring short-term changes.

The measurement of short-term changes in maternal body composition during the post-partum period under field conditions poses many problems: (1) body composition techniques depend on the constancy of the proportions of components or their physical properties and are less suitable for measuring changes; (2) many of the techniques require expensive, technically sophisticated apparatus that is inappropriate to field conditions in many countries; (3) changes in body composition affect some areas of the body more than others so regional as well as whole body approaches are required. The measurements of body weight, triceps and subscapular skinfold thicknesses and upper arm circumference are essential measurements. These can be supplemented with further skinfold thicknesses and circumferences, and possibly body density and body water measurements. There is little to be gained by transforming anthropometric variables into whole body composition indices in these circumstances.

Adipose Tissue↗
PubMed1991

Influence of brisk walking on the broadband ultrasonic attenuation of the calcaneus in previously sedentary women aged 30-61 years.

The amount and type of exercise needed to maintain or increase bone density in women is unclear. The purpose of the present study was to examine the influence of brisk walking on broadband ultrasonic attenuation (BUA) values for the calcaneus in formerly sedentary women aged 30-61 years (mean 44). Twenty-five women followed the program of brisk walking for 1 year and 15 acted as controls. The walkers completed an average (SEM) of 159 (46) minutes/week of brisk walking at a speed of 1.72 (0.05) meters/second, i.e., about 16-18 km/week. Broadband ultrasonic attenuation was determined at baseline and after 1 year. Analysis of variance showed that values were increased (P less than 0.05) for the walkers relative to controls [walkers 103.3 (4.9) versus 116.1 (3.8) dB/MHz; controls 103.6 (5.5) versus 99.6 (5.4) dB/MHz]. We conclude that, in formerly sedentary women, a modest program of a widely acceptable form of exercise, brisk walking, can provoke an increase in this sensitive index of bone condition.

Adult↗
PubMed1990

Body mass index and body energy stores in developing countries.

Body mass index (BMI) is used widely as an index of fatness (the proportion of the body as fat) but its application to the low weight and stature populations in developing countries has not been established. As BMI is an indicator of size (the amounts of fat and fat free masses) as well as fatness, its relation to fatness and interpretation as a measure of energy stores may vary in different groups. Very low BMI reflects low fat and fat free mass, a state for greater concern than low fat mass alone, and possibly more typical of chronic energy deficiency.

Adipose Tissue↗
PubMed1987

Fat patterning in Papua New Guineans: effects of age, sex and acculturation.

For the renewed interest in fat patterning to be fruitful, more information on the biology of fat patterning, particularly normative data are required. Nine skinfold thicknesses were measured in 2312 coastal and highland Papua New Guineans of all ages undergoing acculturation. Principal component analysis of the skinfold data revealed components of fatness and fat patterning. First component scores were typical of the changes in fatness with age and the sex differences expected in these populations. Second component scores of limb-trunk fat patterning showed marked changes with age in both sexes but they stabilised in adulthood. This pattern seemed more affected by maturity although it is usually thought to be a sex-specific pattern. The third component, upper-lower body patterning, was more sexually dimorphic in adults. Marked differences were not observed between the two communities but over a 15-year period fatness levels increased slightly and subcutaneous fat tended to be deposited more centrally.

Acculturation↗