A review of 144 published studies of the relationship between socioeconomic status (SES) and obesity reveals a strong inverse relationship among women in developed societies. The relationship is inconsistent for men and children in developed societies. In developing societies, however, a strong direct relationship exists between SES and obesity among men, women, and children. A review of social attitudes toward obesity and thinness reveals values congruent with the distribution of obesity by SES in different societies. Several variables may mediate the influence of attitudes toward obesity and thinness among women in developed societies that result in the inverse relationship between SES and obesity. They include dietary restraint, physical activity, social mobility, and inheritance.

Socioeconomic Status and Obesity: A Review of the Literature

OBJECTIVES: To re-state the principles underlying the Goldberg cut-off for identifying under-reporters of energy intake, re-examine the physiological principles and update the values to be substituted into the equation for calculating the cut-off, and to examine its use and limitations. RESULTS: New values are suggested for each element of the Goldberg equation. The physical activity level (PAL) for comparison with energy intake:basal metabolic rate (EI:BMR) should be selected to reflect the population under study; the PAL value of 1.55 x BMR is not necessarily the value of choice. The suggested value for average within-subject variation in energy intake is 23% (unchanged), but other sources of variation are increased in the light of new data. For within-subject variation in measured and estimated BMR, 4% and 8.5% respectively are suggested (previously 2.5% and 8%), and for total between-subject variation in PAL, the suggested value is 15% (previously 12.5%). The effect of these changes is to widen the confidence limits and reduce the sensitivity of the cut-off. CONCLUSIONS: The Goldberg cut-off can be used to evaluate the mean population bias in reported energy intake, but information on the activity or lifestyle of the population is needed to choose a suitable PAL energy requirement for comparison. Sensitivity for identifying under-reporters at the individual level is limited. In epidemiological studies information on home, leisure and occupational activity is essential in order to assign subjects to low, medium or high PAL levels before calculating the cut-offs. In small studies, it is desirable to measure energy expenditure, or to calculate individual energy requirements, and to compare energy intake directly with energy expenditure.

Critical evaluation of energy intake using the Goldberg cut-off for energy intake:basal metabolic rate. A practical guide to its calculation, use and limitations

Forage quality can be assessed in terms of the animal performance that is elicited when the forage is offered to the animal. Animal performance is the product of supply, nutrient and energy concentration, intake, digestibility, and metabolism. Typically, forage quality is measured assuming that the forage is freely available and that deficient nutrients other than protein and energy are provided in a supplement. Of the remaining factors affecting forage quality, intake is the most important one affecting animal performance. Reid (1961) listed the amount of forage eaten as the first factor limiting the usefulness of forage-testing schemes. His list also included the effect of concentrates on the amount of forage eaten, degree of selective feeding, and effect of physical form as important information not provided by the forage testing systems used at that time. Unfortunately, intake, substitution rates, selection, and physical form still are not a part of routine forage evaluation systems in the 1990's. Animal performance depends on the intake of digestible and metabolizable nutrients. Of the variation in digestible dry matter (DDM) or digestible energy (DE) intake among animals and feeds, 60 to 90% is related to differences in intake, whereas only 10 to 40% is related to differences in digestibility (Crampton et al., 1960; Reid, 1961). Intake generally accounts for twice as much variability in DDM intake as does digestibility (Milford, 1960; Ingalls et al., 1965). Milford and Minson (1966) observed that DDM intake is more closely correlated with dry matter intake (DMI) than any other feed or animal characteristic. Similarly, high correlations would occur between DMI and metabolizable (ME) or net energy (NE) intake, and between DMI and overall animal performance when forages are fed. The primary importance of intake in assessing forage quality does not mean that digestibility or metabolizability of nutrients are invariant or unimportant. Metabolizability can vary depending on the amounts and ratios of absorbed nutrients, the individual and interacting biochemical pathways of nutrient conversion and the type of animal production (MacRae et al., 1985; Blaxter, 1989). However, differences in the efficiency of converting DE to ME are small compared to differences in intake and digestibility, and the metabolic conversion of DE to ME or NE is typically considered to be relatively constant within type of production, such as maintenance, growth, pregnancy, or lactation (Moe and Tyrrell, 1976; NRC, 1989). Digestibility of forages is more variable than metabolizability, and feces typically are the greatest loss of ingested nutrients and energy. Extensive research has been devoted to measuring digestibility and relating it to feed characteristics because digestibility can be accurately measured with relative ease compared to DMI. Although intake is more important than digestibility in assessing forage quality, progress in understanding the basic factors that affect intake has been hampered by our inability to measure it accurately and to separate the influences of animal and diet on intake. Thus, we routinely use availability information (DE, ME, andNE)

Regulation of Forage Intake

More than 30 different methods have been used to assess physical activity. These methods can be grouped into seven major categories: calorimetry, job classification, survey procedures, physiological markers, behavioral observation, mechanical and electronic monitors, and dietary measures. No single instrument fulfills the criteria of being valid, reliable, and practical while not affecting behavior. The instruments that are very precise tend to be impractical on a population basis. Surveys are the most practical approach in large-scale studies, although little is known about their reliability and validity. Studies employing objective monitoring through heart rate, movement sensors, and doubly labeled water procedures appear promising, but are still experimental and costly. Despite the difficulty of measurement, relatively strong association has been found between physical activity and health, suggesting that, with improvements in assessment techniques, even stronger associations should be seen.

Assessment of physical activity in epidemiologic research: problems and prospects.

HYSIOLOGICAL STUDY of man's food needs and capacity for physical work began on a systematic basis about seventy years ago. Following upon Atwater's classic experiments with a human calorimeter at the end of the last century, the validity of using rates of oxygen consumption as the basis for measuring energy expenditure (indirect calorimetry) was firmly established. Throughout this early period rates of energy expenditure during a variety of human activities were recorded. Recently there has been a renewal of interest in such measurements. This is in part due to the development of apparatus which can be conveniently applied under many industrial conditions, where it had not hitherto been practicable to use the more cumbersome apparatus designed for laboratory studies. Also, methods of work in many industries and in agriculture have changed markedly. Machines increasingly do the work formerly done by manual labor. This change is more noticeable in the highly industrialized coun.tries, but it is spreading throughout the world. Much of 'heavy' industry now consists in controlling large sources of mechanical power by means of levers and switches and the work for the human operator is often 'light.' Further, with increased productiveness there has been a shortening of the working week. There is now time and opportunity for recreations on a scale altogether different from fifty years ago. Many recreations demand much expenditure of physical energy and a wage earner may use his muscles more in his leisure time than during his earning hours. These factors call for new assessments of human energy expenditure , Indirect calorimetry enables the energy expended to be determined while a de& nite activity is undertaken for a limited period of time, usually measured in minutes. More information is necessa.ry to assess the energy expenditure in daily life. This energy has, of course, to be provided by the food, if health and activity are to be maintained. In the past most assessments of total energy needs have been made from dietary studies. This was the method used by Voit, Atwater and others, who first stated the energy expenditure of a variety of occupations, after analyzing records of the diets consumed by persons of known employment. The method is open to the theoretical objection that it assumes that the diets consumed provide exactly enough energy with no surplus or deficiency. It provides no direct yardstick of requirement. Indeed in the East and elsewhere large numbers of …

Human Energy Expenditure

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J. G. Fletcher

Papers

The Energy Expenditure and Food Intake of Individual Men