Short communication Appetitive traits in children. New evidence for associations with weight and a common, obesity-associated genetic variant Susan Carnell a, *, Jane Wardle b a New York Obesity Research Center, St Luke’s-Roosevelt Hospital Center, Babcock Building 10th Floor, Room 1020, 1111 Amsterdam Avenue, New York, NY 10025, USA b Cancer Research UK Health Behaviour Research Centre, Department of Epidemiology & Public Health, Gower Street, University College London, London, WC1E 6BT, UK The ‘obesogenic’ environment is powerful and pervasive, but nonetheless there is enormous variation in weight among both adults and children, and weight variability in the population may even be increasing (Jolliffe, 2004; Romon, Duhamel, Collinet, & Weill, 2005; Wardle & Boniface, 2008). One possible explanation is that individuals differ in their susceptibility to environmental pressures that promote excessive energy intake or minimize the need for physical activity (Carnell & Wardle, 2008a, 2008b). In support of this possibility, a number of behavioural studies conducted in non-clinical samples of adults in the 1960s and 1970s suggested that obese individuals may display a cluster of ‘risky’ appetite-related traits which normal-weight individuals do not, including low responsiveness to internal satiety signals such as gut peptide release or gastric distension (satiety responsiveness) (Meyer & Pudel, 1972; Stunkard & Fox, 1971; Stunkard & Kaplan, 1977), and high responsiveness to external food cues such as the sight or smell of food (food cue responsiveness) (Schachter, Goldman, & Gordon, 1968; Schachter & Gross, 1968). Failure to replicate some of these results using similar manipulations in women attending weight loss clinics (Rodin, Slochower, & Fleming, 1977) led the ‘externality’ theory to fall from favour, but may have been attributable to higher levels of restraint and social desirability. The balance of the evidence suggests that satiety responsiveness and food cue responsiveness are likely contributors to differences in environmental susceptibility to common obesity. Appetitive traits in obese children: existing case-control studies Satiety responsiveness and food cue responsiveness also appear to differ between obese and normal-weight children. For example, Jansen et al. (2003) showed that obese children demonstrate poorer compensation for previous energy intake (a presumed index of satiety responsiveness) compared with lean children. Obese children also tend to eat faster (Barkeling, Ekman, & Rossner, 1992; Drabman, Cordua, Hammer, Jarvie, & Horton, 1979), and one study observed an absence of the typical pattern of deceleration during a meal (Barkeling et al., 1992), both of which findings might be interpreted as demonstrating insensitivity to increasing full- ness. Evidence for physiological correlates of this lack of sensitivity in children is limited, but one study found that obese children had lower levels of the satiety hormone PYY (Roth et al., 2005). This suggests either that peptide hormone profiles could be associated with obesity risk, or that they are secondary to obesity and acting only as maintaining factors. In terms of food cue responsiveness, a number of studies have now shown that, compared with lean children, obese children show greater intake of palatable snack foods in the absence of hunger (Birch & Fisher, 2000; Butte et al., 2007; Fisher et al., 2007). This suggests that the presence of food overwhelms the opposing satiety signals which may be weaker or absent in obese individuals. Another study also observed greater intake following exposure to the smell of palatable foods (Jansen et al., 2003), suggesting that intake may be initiated by a range of cues. There are few fMRI studies in this area and even fewer in children, but new results suggest that obese children, like obese adults, show Appetite 53 (2009) 260–263 ARTICLE INFO Article history: Received 11 January 2009 Received in revised form 28 April 2009 Accepted 19 July 2009 Keywords: Appetite External eating Satiety sensitivity High risk Child obesity ABSTRACT The ‘obesogenic’ environment has the potential to affect everyone, but nonetheless, individuals differ in body weight, suggesting variation in susceptibility to environmental influences. Behavioural studies indicate that obese children experience low responsiveness to internal satiety signals and high responsiveness to external food cues. In this paper we describe the results of new studies using behavioural tests and psychometric questionnaires in large samples to show that individual variation in these appetitive traits relates to body weight throughout the distribution. We also describe twin studies and genetic association studies supporting a strong genetic component to appetite. Implications include the early identification of ‘at risk’ children, and interventions to modify appetitive traits. ß 2009 Elsevier Ltd. All rights reserved. * Corresponding author. E-mail address: susan.carnell@gmail.com (S. Carnell). Contents lists available at ScienceDirect Appetite journal homepage: www.elsevier.com/locate/appet 0195-6663/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.appet.2009.07.014