The genetics of human fatness

Abstract

Studies on the quantitative genetics of fatness are reviewed in the framework of the twin, adoption-cohabitation, and familial aggregation methodologies. Low to moderate heritability of adult static fatness is evident. Somewhat less than one-third of the variation appears ascribable to genetic causes. Genetic factors may play a greater role in childhood fatness, especially during adolescence. Comparison of studies is made difficult by many methodological shortcomings. These include a rarity of studies of adult firstdegree relatives (adulthood being the period in which fatness has the greatest health consequences), different criteria of body fatness among studies, a lack of a full variety of genetic and adoptive relationships, inadequate sample sizes (especially in twin studies), and unreported precision of fatness variables. Fatness change in the life cycle and the anatomical placement of fat are important modifiers of the health effects of obesity. Yet the genetics of these characteristics are little understood. Innovative statistical methods and study designsincluding path analysis, the family set method, and families of monozygous twins need wider application to the genetics of human fatness.Human obesity, or fatness, and its heredity have been reviewed in the past (Steinberg, 1960;Mayer, 1965;Seltzer and Mayer, 1966;Seltzer, 1969;Hunt, 1972;Foch and McClearn, 1980;Forbes, 1982). Early studies relied on clinical appraisals of obesity or indices derived from weight and height (Davenport, 1923;Dunlop and Lyon, 1931;Ellis and Tallerman, 1934;Gurney, 1936;Rony, 1940;Angel, 1949). Later studies have used more direct measurements of body fatness such as subcutaneous fat or body density (Reynolds, 1951;Hewitt, 1957;Tanner and Israelsohn, 1963;Howells, 1966; Brook et aI., 1975;Garn et al, 1975;Borjeson, 1962Borjeson, , 1964Borjeson, , 1976Wolanski, 1976;Hawk and Brook, 1979; Savard et aI., 1983). A series of recent adoption studies have also attempted to assess the contribution of environment to familial aggregation of fatness (Shenker et aI., 1974; Garn et aI., 1976a Garn et aI., ,b, 1977a Garn et aI., ,b, 1979a Biron et aI., 1977; Hartz et aI., 1977). Other techniques have been used to separate the contribution of genes and environment to familial resemblance in body weight and fatness such as partial correlation (Mueller, 1977(Mueller, , 1978Mueller and Reid, 1979;Bouchard, 1980;Mueller and Malina, 1980), path analysis (Rao et aI., 1975; Bouchard et aI., 1980b), and families of identical twins (Meany et aI., unpublished). Some studies on the genetics of growth have included measurements indirectly related to fatness such as body mass index, body circumferences, and somatotypes (Bowles, 1932; Bayley, 1954;Vandenberg, 1962;Withers, 1964;McHenry and Giles, 1971;Susanne, 1975; Bouchard et aI., 1980a). Yet these have not generally been included in past reviews on the genetics of fatness. This review is intended to bring this information together in a way which will critically assess the role of genes in hu...

Assessment of adiposity in an Indian population: Familial correlations

“…The overall parent-offspring and sibling correlations for BMI, estimated under model IV (FS = FD = MS = MD and BB = SS = BS), are in relatively good agreement with the majority of published studies [see Mueller, 1983 andPermse, 1988 for reviews of this literature]. This is true for both age (FS = FD = MS = MD = 0.24; BB=SS=BS=0.40),andage-andenergy-(parent-child,FS=FD=MS=MD=0.17; BB = SS = BS = 0.40) adjusted BMI.…”

Resting Metabolic Rate in Monozygotic and Dizygotic Twins

“…Studies on human have indicated that genetic variation contributes to interindividual differences in body fatness [16,19]. In our laboratory, skinfold thicknesses as well as body composition measurements, using an underwater weighing technique, have been used in the study of the contribution of heredity on body fatness level.…”

“…Excess body fat is thought to occur as a result of genetic causes and/or unfavourable lifestyle [14]. From about one fourth to one third of the population variance in adult fatness have been considered to result from inherited biological differences [1,16,19].…”

The diabetes alert study: Growth, fatness, and fat patterning, adolescence through adulthood in Mexican Americans

“…We compare diabetics and their non diabetic relatives in a n effort to confirm or reject the hypothesis that Type I1 diabetes is associated with concentration of fatness on the upper part of the body (Vague, 1956;Feldman et al, 1969;Kissebah et al, 1982;Szathmary and Holt, 1983). Then we construct an index of fat patterning by techniques developed earlier to identify periods in the life cycle of rapid development of fat toward the central and upper body and away from the extremities (Mueller and Reid, 1979;Ramirez and Mueller, 1980;Mueller and Stallones, 1981;Mueller and Wohlleb, 1981;Mueller, 1982;Malina et al, 1982;Stallones et al, 1982;Mueller et al, 1982;Mueller 1983).…”