The effect of 6 weeks of overfeeding on the body weight, body composition, and energy metabolism of young men.

The effect of overfeeding on the body weight, body fat, water content, energy expenditure, and digestibility of energy and nitrogen was investigated over 42 days in six young men. The metabolic rates in standard situations of work and rest were determined. Energy intakes were apparently increased by 6.2 MJ/day and energy expenditure fell slightly by 0.3 MG/day during overfeeding. Fecal and urinary losses of energy were a similar proportion of the gross energy intake in control and overfeeding periods (8%). Metabolizable energy intakes calculated from food tables agreed well with values derived from digestibility measurements in the control period (mean difference = +2%) but not in the overfeeding period (+8%). The implications of this are discussed. Mean body weight gain was 6.0 kg, 10% of initial weight; mean fat gain was 3.7 kg and water gain 1.8 liter. There were considerable interindividual differences in the weight and fat gain for a given excess energy intake. Metabolic rates in standard tasks were 10% higher at the end of overfeeding but expressed as kilojoules per kilogram per minute were similar to control values. Mean energy gain (144 MJ = fat gain X 39 kJ/g) was less than excess energy intake even allowing for overestimation of intakes using food tables and increases in metabolic rate. Such a discrepancy is unlikely to be due to unmeasured increases in metabolic rate but could have arisen from errors in the calculation of the variables involved. In this study where moderate weight gains were achieved by overfeeding mainly fat, increases in metabolic rate appear to be associated with increased body size and tissue gain rather than a luxuskonsumption mechanism.

Food intake, its relationship to body weight and age, and its apparent nutritional adequacy in New Guinean children.

Previous nutritional investigations in New Guinea have shown low intakes of protein and of energy yet the nutritional status of children and their ability to thrive have been regarded as better than could be expected. To investigate this apparent paradox, the dietary intakes of 482 New Guinean children, aged 1-18 years, living in two contrasting environments near the coast (Kaul) and in a highland region (Lufa) were determined by a weighed individual inventory method over 5-7 consecutive days. Body weights and skinfold thicknesses were lower than those of European children of comparable ages. These findings are to be reported and discussed more fully in a separate publication. Roots and tubers provided most of the energy and protein in the bulky, vegetable diets. The contribution of foods bought in local trade stores was higher than has previously been reported. Fat intakes were low, supplying 17% of the dietary energy in Kaul and 10% in Lufa. Protein intakes were similarly low, representing only 6% of dietary energy. The chemical scores of the protein calculated using the latest suggested amino acid scoring pattern (FAO/WHO, 1973) were high, 75-95. Using the previous pattern, these were 57-64. The adequacy of the energy and protein contents of individual diets was assessed using the FAO/WHO (1973) standards. An energy deficit was more common than a protein deficit. A considerable proportion of the children (42% in Kaul and 20% in Lufa) had dietary intakes which were apparently deficient in energy or protein, but this finding did not correspond to other signs of undernutrition. This suggests that current standards may still be set too high for some groups or that adaptations to suboptimal dietary intakes occur that are not disclosed by the usual techniques of assessing nutritional status.

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.

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.

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.

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.

Measurement and interpretation issues in laboratory and field studies of energy expenditure.

The methods for measuring energy expenditure in the laboratory and the field are described and critically appraised and the criteria for reliable and valid measurements identified. Variation and adaptation in the energy costs of activities and the total daily energy expenditure are considered in the context of discriminating between what is variation and adaptation and what is honest error. This involves issues of comparative energetics and standardization and oxygen uptake kinetics, which are frequently neglected or ignored. The energetics of physical work, where many of the problems arise, are examined. It is technically feasible to measure energy expenditure with high accuracy, but the methods required, calorimeter rooms and doubly labelled water, are not widely available or applicable. The field methods, the factorial method of diary record of activities and their energy costs, and the heart rate methods are of acceptable accuracy for groups but less so for individuals. When using energy costs from the literature, as has been common in human biology, several problems arise. The sample sizes are small and of unknown provenance, and there is no information on variability or on whether the values are based on continuous or intermittent work. The problem of how to allow for differences in size and composition has been tackled with convenience rather than concepts. It is recommended that isometric scaling, using kcal/kg, be avoided and allometric scaling by, e.g., analysis of covariance, be used to remove the effects of size and composition. In investigations of variation and adaptation in the efficiency of work, the effects of oxygen uptake kinetics and of anaerobic metabolism must be considered. © 1996 Wiley-Liss, Inc.

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.

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.

Body mass index and nutritional status: the effect of adjusting body mass index for the relative sitting height on estimates of the prevalence of chronic energy deficiency, overweight and obesity.

Low body mass index (BMI) has been proposed as a practical measure of adult chronic energy deficiency (CED), although it was well-known limitations. One of these is that its interpretation is complicated by the influence of body proportions, in particular the relative leg length. This has been quantified by examining data collected before 1970 of 349 adult Australian Aborigines following a largely traditional way of life. These Australian Aborigines exhibited low sitting height: stature ratios (SH/S), 0.48± 0.02, (mean ± sd), range 0.41-0.54, ie they are relatively long legged, and low BMI, 19.9± 3.2, range 12-30 kg/m2. Thirty percent of individuals had BMI less than 18.5 kg/m2, a suggested cut-off for CED. The regression of BMI on SH/S was determined in men and women separately but found by covariance analysis not to be different and a common equation for both sexes was calculated. When BMIs were standardized to a SH/S of 0.52, a value found in Europeans and other Indo-Mediterraneans, the percentage classed as chronically energy-deficient fell to 7%. In Asians and indigenous Americans with their high SH/S, the percentage of the population with overweight and obesity could be overestimated and the extent of CED underestimated. In populations with a mean SH/S of 0.52, such as Europeans and Pacific peoples, standardizing SH/S to 0.52 would not effect the prevalence of CED or overweight and obesity but could move individuals across diagnostic boundaries as there is variability in SH/S in all population groups. In conclusion, when using BMI to assess energy nutritional status single cut-offs are not applicable to all individuals and population groups without allowance for the body form and type.

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.

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.

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.

PIP: The problems attendant with measurement of maternal body composition shortterm changes during the postpartum period and under field conditions include the requirement for constancy of components, costliness of techniques, and the need for regional and whole body approaches. The in vitro method of measurement includes anatomical dissection and chemical analysis. The in vivo measurement comprises whole body (density, body water, potassium, elemental, and electrical properties assessment), regional (subcutaneous adipose tissue with skinfold, ultrasound, near infrared interactance), cross-sectional areas (skinfolds and circumferences, ultrasound, and computed tomography [CT], volumes (skinfolds, circumferences, lengths, and CT), and estimations (anthropometry). Postpartum changes in body composition include reversal of weight gain induced by pregnancy: 7-8 kg gain in developing countries and 12-14 kg gain in developed countries 2-4 kg of which is fat. 75% of the reduction is adipose tissue and 25% is lean body mass. Choice of methods depends of the purpose, precision of measurement data, cost and availability of instruments (radiography, CT, magnetic resonance imaging, deuterium dilution, bio-impedance meters), and acceptance of the subject (simple, noninvasive procedures). Among these anthropometry scores high on feasibility and desirability, whole techniques requiring elaborate equipment score low. In vivo body composition techniques are best if a 3-compartment model of fat, water, and protein is employed. Thus, anthropometric measurement of weight, height, triceps and subscapular skinfolds, and upper arm circumference is the method of choice.

Changes in patterns of growth and nutritional anthropometry in two rural modernizing Papua New Guinea communities.

In Papua New Guinea growth is slow and adult body size is small. This is often considered an adaptation to the low energy and nutrient densities of the diets in which tubers and root crops predominate. Social and economic change have been a feature of Papua New Guinea, particularly in recent times. In 1969 the human biology of two contrasting communities, one coastal with a long interaction with external influences and cash cropping, the other a highland community with a history of more recent contacts, was investigated. In 1984 repeat measurements of nutritional anthropometry were made on the villagers and those born in the previous 14 years. The coastal boys and girls were taller and heavier in 1984 compared with 1969 but remained below the 5th percentile of reference North American data. Increases were also found in the highland children, particularly girls, but significantly lower means were found in children under 2 years. Although stunting was less common in the coastal children in 1984, 156 cases (37%) versus 175 cases (43%) (chi 2 = 7.69, rho < 0.05), wasting increased in prevalence from 11 cases (3%) to 20 cases (5%) (n.s.), either because of recent food shortages or because height change was greater than weight change. Stunting rose by 3% to 53% (165 cases) in highland children (chi 2 = 7.24, p < 0.05). In adults, heights were 2-3 cm greater in 1984 than 1969, and weights 2-3 kg greater, with peak differences in the 30-39-year-olds. The percentage of coastal women with body mass indices of less than 18.5 kg/m2 fell from 32% to 15% (chi 2 = 27.4, p < 0.01). Mid-upper arm circumferences and triceps skinfolds were significantly higher in all groups. National and regional data suggest that the communities were better off in 1984 than 1969, but social and economic changes were associated with variable benefits in growth and nutritional status.

PIP: The slow growth, short stature, and light weight characteristic of populations in Papua New Guinea are generally assumed to reflect an adaptation to the low energy and nutrient densities of diets in which tubers and root crops predominate. In recent years, however, Papua New Guinea has moved toward cash-cropping, food import, and a cash economy. To assess the effects of modernization on growth and nutritional anthropometry, a large multidisciplinary study of an island (Kaul) and a highland (Lufa) community conducted in 1969 was replicated in 1984. 62% of those in the first study were available for remeasurement. Although the coastal children born during 1970-84 were taller in 1984 than their 1969 counterparts, they remained below the 5th percentile of reference North American data. Height increases also occurred over time in the highland children, especially among girls, but means were significantly lower in 1984 than 1969 in those under 2 years of age. Anthropometric deficits were greatest at about 15 years of age in both communities. The incidence of stunting in coastal children declined from 43% in 1969 to 37% in 1984, but wasting increased from 3% to 5%. In highland children, stunting rose from 50% to 53%; there was no wasting. In adults, heights were 2-3 cm greater in 1984 than in 1969 and weights increased by 2-3 kg. The percentage of coastal women with a body mass index under 18.5 kg/m2 decreased from 32% to 15% between studies and significant improvements in mid-arm circumferences and triceps skinfold were recorded in all groups. Although drought-induced, curtailed garden productivity and infectious diseases may have deflated the magnitude of change since 1969, these findings suggest that modernization has not had the expected dramatic effect on nutritional status in Papua New Guinea.

Relative sitting height and the interpretation of the body mass index.

The body mass index (BMI) is being used widely as an index of overweight and undernutrition. The effects of variations of shape as evinced by relative sitting height (sitting height/stature, SH/S) on BMI were determined using mean data from 95 samples of men and 63 samples of women of non-European origin, representing 18,000 individuals. The linear regression coefficients of BMI on SH/S (b +/- standard error) were 0.78 +/- 0.16 (t = 4.8) in men and 1.19 +/- 0.22 (t = 5.3) in women. Correlations coefficients were 0.45 and 0.56, respectively. These regression coefficients compare with a predicted change of 0.9 kg/m2 per 0.01 difference in SH/S using a modelling approach. The wide variation within and between populations precludes a simple adjustment for SH/S, and in the interpretation of BMI additional anthropometric measurements may be necessary.

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.

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.

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.