seemed to be inherent in an individual’s biological/genetic makeup. That is, even after the study team had obese subjects lose a considerable amount of weight (8 kg) and had lean individuals gain weight (4 kg), the two subject groups did not change their original posture allocation.

These data suggest that interindividual differences in posture allocation (i.e., NEAT) may be genetically determined. The authors of the respective research [117] speculate that “( … ) obese and lean individuals respond differently to the environmental cues that promote sedentary behavior” (p. 586). This type of research, again, provides a rich ground to further integrate more genetic-based research with studies on the social environment.

5.
GENETIC INFLUENCES ON OBESITY AND OBESITY-PROMOTING BEHAVIORS

This section reviews evidence for genetic influences on obesity and obesity-promoting behaviors, corresponding to paths b and c in Figure C-1. The section is divided into two subsections. Subsection 5a examines evidence for genetic influences on BMI and body fat measure, while subsection 5b examines evidence for genetic influences on obesity-promoting behaviors related to food intake (i.e., pathway b in Figure C-1). Within each subsection, data are presented for studies that estimate heritability of the phenotype, followed by studies that tested the influence of specific genes or genomic regions.

5a.
Genetic Influences on BMI and Fat Mass

i.
Heritability of BMI and Fat Mass

“Heritability” refers to the extent to which variability in a trait is influenced by genetic variations within a population, and can be subdivided into “narrow-sense” or “broad-sense” heritabilities [118]. The former refers solely to additive genetic influences on the trait, whereas the latter refers to nonadditive interactions among genes. Beyond heritability, the remaining variance in weight status is due to environmental influences which can be partitioned into “shared environment” or the “nonshared environment” influences. Shared environment refers to aspects of the home environment that are perfectly shared by siblings from the same home (e.g., food in the home cupboards, the number of television sets at home). The nonshared environment refers to those aspects of the environment that are uncorrelated among siblings (e.g., differential interactions with parents or peers, or differential life experiences). Apropos to this report, specific as-



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