Factors affecting body density and thickness of subcutaneous fat. Data on 518 Canadian city dwellers

Modern diet and metabolic variance--a recipe for disaster?

OBJECTIVE

Recently, a positive correlation between alanine transaminase activity and body mass was established among healthy young individuals of normal weight. Here we explore further this relationship and propose a physiological rationale for this link.

DESIGN

Cross-sectional statistical analysis of adiposity across large samples of adults differing by age, diet and lifestyle.

SUBJECTS

46,684 19-20 years old Swiss male conscripts and published data on 1000 Eskimos, 518 Toronto residents and 97,000 North American Adventists.

MEASUREMENTS

Serum concentrations of the alanine transaminase, post-prandial glucose levels, cholesterol, body height and weight, blood pressure and routine blood analysis (thrombocytes and leukocytes) for Swiss conscripts. Adiposity measures and dietary information for other groups were also obtained.

RESULTS

Stepwise multiple regression after correction for random errors of physiological tests showed that 28% of the total variance in body mass is associated with ALT concentrations. This relationship remained significant when only metabolically healthy (as defined by the American Heart Association) Swiss conscripts were selected. The data indicated that high protein only or high carbohydrate only diets are associated with lower levels of obesity than a diet combining proteins and carbohydrates.

CONCLUSION

Elevated levels of alanine transaminase, and likely other transaminases, may result in overactivity of the alanine cycle that produces pyruvate from protein. When a mixed meal of protein, carbohydrate and fat is consumed, carbohydrates and fats are digested faster and metabolised to satisfy body's energetic needs while slower digested protein is ultimately converted to malonyl CoA and stored as fat. Chronicity of this sequence is proposed to cause accumulation of somatic fat stores and thus obesity.

Is alcohol consumption a risk factor for weight gain and obesity?

Alcohol represents an important source of energy. Despite its comparatively high energy content of 7.1 g/kcal, it is still controversial whether moderate amounts of alcohol represent a risk factor for weight gain and obesity. Epidemiologic data showed a positive, negative, or no relationship between alcohol intake and body weight. Despite the difficulty in assessing alcohol intake as well as controlling for different confounders of the energy-balance equation, the conflicting epidemiologic data can be explained in most instances. Every component of the energy-balance equation is affected by the ingestion of alcohol. Moderate amounts of alcohol enhance energy intake due to the caloric content of the alcohol as well as its appetite-enhancing effects. Alcohol-induced thermogenesis is approximately 20% in healthy nonalcoholic subjects, i.e., moderate alcohol consumers, which is higher than for other energy substrates but considerably lower than in heavy alcohol consumers. This would suggest that a major fraction of the alcohol energy represents a navailable energy source for ATP synthesis in moderate non-daily alcohol consumers. Experimental evidence from several metabolic studies showed a suppression of lipid oxidation by alcohol and thus the enhancement of a positive fat balance. The nonoxidized fat is preferentially deposited in the abdominal area. The experimental metabolic evidence suggests that the consumption of moderate amounts of alcohol has to be accounted for in the energy-balance equation and may represent a risk factor for the development of a positive energy balance and thus weight gain. In the heavy alcohol consumer and eventually also in daily moderate alcohol consumers, a larger fraction of the alcohol energy might not be an available source of energy due to the induction of the microsomal ethanol-oxidizing system (MEOS). Experimental data in combination with epidemiologic findings suggest that alcohol energy counts more in moderate nondaily alcohol consumers than in some moderate daily and all heavy consumers. Accordingly the question is not "Whether alcohol calories do count" but "How much do alcohol calories count?". There seems to be a large individual variability according to the absolute amount of alcohol consumed, the drinking frequency as well as genetic factors. Presently it can be said that alcohol calories count more in moderate nondaily consumers than in daily (heavy) consumers. Further, they count more in combination with a high-fat diet and in overweight and obese subjects.

Effects of alcohol on energy metabolism and body weight regulation: is alcohol a risk factor for obesity?

Some studies have suggested that drinking in moderation may be beneficial for health, but many of these studies do not address body weight. Evidence suggests that consuming moderate amounts of alcohol is a risk factor for obesity, which is a risk factor for several adverse health outcomes. Recommendations regarding alcohol intake thus should take into account a variety of factors, including baseline body weight, location of body fat, and overall diet.

The validity generalization of skinfolds as measures of body density

Validity generalization was used to ascertain the generalizability of skinfolds as measures of body density. A literature search was conducted to locate studies employing skinfolds as predictors of body density using hydrostatic weighing as the criterion test. The sites examined included the triceps, subscapula, suprailiac, abdomen, front thigh, midaxillary, and the log sum of the biceps, triceps, suprailiac, and subscapula. Results indicated that no single sites were generalizable across all subjects; however, the log sum of the four sites was generalizable. For adult males, the suprailiac and midaxillary sites were generalizable, while the subscapular site was generalizable for women. No sites were generalizable for boys, while the triceps site was generalizable for girls. Suggestions are provided for additional research.

Histologic changes in skin associated with aging

This is a review of histologic changes noted in the skin of elderly individuals. Among the epidermal changes associated with skin aging are a flattened dermal-epidermal junction, giving the appearance of atrophy and cellular heterogeneity. The melanocyte density declines slowly, and the Langerhans cells decrease in number with advancing age. Among the dermal changes are attenuation in the number and diameter of elastic fibers in the papillary dermis, an increase in number and thickness of the same fibers in the reticular dermis, and a coarsening of collagen fibers with an increase in density of the collagen network. A decrease in the dermal cell population as well as a functional decline in glandular activity are also noted with intrinsic aging. A decline in hair number, rate of growth, and diameter, along with a slowing of the rate of growth of nails, have been well documented with progressive aging.

Principal components analysis of physical growth in savannah baboons

Morphometric data collected from 118 male and 169 female savannah baboons (Papio cynocephalus anubis) aged between birth and 5.5 years were analyzed to describe the morphology and physical growth of this species. Measurements included weight, crown-rump length, triceps circumference, and skinfolds at the neck, subscapular, suprailiac, and triceps anatomical sites. Principal components analyses were applied to the data to provide multivariate assessments of morphological patterning among the variables. These analyses resulted in the extraction of two unrotated orthogonal components that accounted for 88% of the overall sample variation. The first component accounted for 77% of the variation and represents an axis of overall body size. The second component represents an axis of shape variation that contrasts body size with fat patterning, and was interpreted as a measure of body leanness. Individual component scores were computed for determining age, gender, and age-by-gender interaction effects. Both components were found to be age dependent for both genders. Males and females shared similar age patterning along the two components; however, gender differences did occur in patterning along the two components; however, gender differences did occur in respect to leanness. The multivariate measure of overall body size increased for both genders similarly with advancing age. Age patterning along the leanness component was described as a decrease from birth to 1 year, followed by an increase in leanness in older ages. Females had a delayed and significantly less intense increase in leanness relative to males.

Structural and functional changes of normal aging skin

Solar-induced cutaneous changes are more prevalent and profound in older persons and, thus, are often inappropriately attributed to the aging process, per se. Structural and functional alterations caused by intrinsic aging and independent of environmental insults are now recognized in the skin of elderly individuals. Structurally the aged epidermis likely becomes thinner, the corneocytes become less adherent to one another, and there is flattening of the dermoepidermal interface. The number of melanocytes and Langerhans cells is decreased. The dermis becomes atrophic and it is relatively acellular and avascular. Dermal collagen, elastin, and glycosaminoglycans are altered. The subcutaneous tissue is diminished in some areas, especially the face, shins, hands, and feet, while in others, particularly the abdomen in men and the thighs in women, it is increased. The number of eccrine glands is reduced and both the eccrine and apocrine glands undergo attenuation. Sebaceous glands tend to increase in size but paradoxically their secretory output is lessened. The nail plate is generally thinned, the surface ridged and lusterless, and the lunula decreased in size. There is a progressive reduction in the density of hair follicles per unit area on the face and scalp, independent of male-pattern alopecia. The hair shaft diameter is generally reduced but in some areas, especially the ears, nose, and eyebrows of men and the upper lip and chin in women, it is increased as vellus hairs convert to cosmetically compromising terminal hairs. Functional alterations noted in the skin of elderly persons include a decreased growth rate of the epidermis, hair, and nails, delayed wound healing, reduced dermal clearance of fluids and foreign materials, and compromised vascular responsiveness. Eccrine and apocrine secretions are diminished. The cutaneous immune and inflammatory responses are impaired, particularly cell-mediated immunity. Clinical correlates of these intrinsic aging changes of the skin include alopecia, pallor, xerosis, an increased number of benign and malignant epidermal neoplasms, increased susceptibility to blister formation, predisposition to injury of the dermis and underlying tissues, delayed onset and resolution of blisters and wheals, persistent contact dermatitis, impaired tanning response to ultraviolet light, increased risk for wound infections, prolongation of therapy necessary for onychomycosis, and thermoregulatory disturbances.

Anatomical distribution of subcutaneous fat and its description by multivariate methods: how valid are principal components?

Principal components analyses of subcutaneous fat measurements covering arm, trunk, and leg areas of the body were performed on 44 samples varying in sex, age, and ethnicity of subjects; measurement technique; and number of sites studied. Three major components emerged, similar in all samples: A first component of obesity, a second component of anatomical fat distribution contrasting trunk and extremity fat, and a third distributional component contrasting leg and arm fat. These components did not appear to vary with age (school children to older adults), sex, ethnicity (Black-White), technique (caliper, ultrasound, or X-rays), or number of sites (five to 13). The three major components are similar to vectors or obesity and relative fat patterning reported earlier by anthroposcopic (Skerlj et al., 1953) and graphic (Garn, 1955) methods. One of the pattern components (trunk-extremity) appears to correspond to a body build continuum associated with adult chronic diseases (Vague, 1956). The stability of these components among samples that differ in several characteristics suggests the validity of these components in describing aspects of body build of anthropological and epidemiological importance.

Body fat in urban and rural male college students of eastern India

Male college students (N = 381) residing in several districts of Eastern India, classified into two groups, urban (N = 193) and rural (N = 188), were studied by anthropometric measurements of skinfold thicknesses in several sites of the body to determine their body fat content. The mean value of percentage of body fat was found to be significantly higher (P less than 0.001) in the urban group of students (12.07 +/- 3.04) than in the rurals (11.04 +/- 2.63). The mean values of skinfold thicknesses of the biceps, triceps, and subscapular regions were also found to be higher in urbans (P less than 0.01), but no such significant differences in mean values of supra-iliac and abdominal skinfolds were found between the two groups of students. Most of the subjects of both the groups had a greater thickness of the abdominal skinfold compared to thickness of the biceps, triceps, and suprailiac skinfolds. It was found that the college students of Eastern India were leaner than the youths of North America, Europe, Japan, and Northern India.

Current controversies in childhood obesity

The conclusions that one can state with assurance are remarkably few. Adiposity in children is best monitored clinically by the measurement of skin-fold thickness. The likelihood that obesity will progress from infancy to childhood to adult life is still questionable and may be more important in the individual child than as a significant cause of adult obesity. Behavioral and social factors pedominate in etiology, yet biologic factors, including genetic, are also involved. Behavioral and social factors are critical in the significance of obesity to the individual. Although there are definite disease hazards, they appear to be predominantly confined to the very obese. The best treatment appears to be prophylaxis, again heavily involving behavioral and social factors as well as the wide-spread distribution of sound nutritional information. When prophylaxis fails, the behavioral modification approach to therapy currently holds the greatest promise.