Stress and the relative reinforcing value of food in female binge eaters.

The purpose of this study was to examine the independent and interactive effects of stress reactivity and binge eating (BE) status on changes in the relative reinforcing value of snack foods. The relative reinforcing value of snack foods was assessed in binge eaters and non-binge eaters across a stress-induction session (after 3-minutes of anticipation of giving a speech) or a control day (after 3-minutes of reading magazines), with order of conditions counterbalanced. Subjects were divided into four groups based on scores on the Binge Eating Scale (BES) and changes in perceived stress: Binge eaters/low stress reactivity (n=12), binge eaters/high stress reactivity (n=10), non-binge eaters/low stress reactivity (n=6), non-binge eaters/high stress reactivity (n=9). Dietary restraint, hunger, disinhibition, and hedonics were measured by self-report. Body composition was estimated by body mass index (BMI=weight in kilograms divided by height in metres squared). The relative reinforcing value of snack food was influenced differently by binge status and stress reactivity in the stress and control conditions (p<0.05). Binge eaters who reacted to stress earned more snack food points (p<0.001) in stress condition, but non-binge eaters who showed high stress reactivity earned less points for snack food in stress condition (p<0.05). This same pattern of results remained after statistically controlling for body mass index (BMI) and dietary restraint. Findings suggest that reactivity to interpersonal or ego-related stress increases the relative reinforcing value of food in binge eaters but decreases the relative reinforcing value of snack food in non-binge eaters, and these findings appear to be independent of dietary restraint and BMI.

Effects of modifying physical activity and sedentary behavior on psychosocial adjustment in overweight/obese children.

OBJECTIVES: To evaluate the relationship between changes in physical activity (PA), sedentary behavior, and physical self-perceptions and global self-worth in 30, 8-12 years old, overweight/obese children (13 boys, 17 girls). METHODS: Secondary analyses from a randomized controlled trial designed to increase PA and reduce sedentary behavior. PA was measured by accelerometers worn by participants every day for 8 weeks. Sedentary behavior, defined as minutes per day spent in television viewing, was assessed by self-report. RESULTS: Increases in PA were associated with increases in perceived physical conditioning (r = .54, p < .01), body satisfaction (r = .55, p < .01), and overall physical self-worth (r = .44, p < .05) independent of changes in body mass index (BMI). Reductions in TV viewing were also related to increased physical and global self-worth. CONCLUSIONS: Increases in PA are associated with improvements in physical self-perceptions but not global self-worth, while reductions in TV viewing are associated with increased physical and global self-worth, and these psychosocial benefits appear to be independent of changes in adiposity.

Dietary restraint, anxiety, and the relative reinforcing value of snack food in non-obese women.

This study tested the independent and interactive effects of anxiety and dietary restraint on the relative reinforcing value of snack food. Thirty non-obese, female university students were assigned to one of four groups based on median split scores on measures of dietary restraint and state-anxiety: low-restraint/low-anxiety (n=7), low-restraint/high-anxiety (n=7), high-restraint/low-anxiety (n=9), and high-restraint/high-anxiety (n=7). Participants were provided the choice to earn points for palatable snack foods or fruits and vegetables using a computerized concurrent schedules choice task. The behavioural cost to gain access to snack foods increased across trials, whereas the cost to gain access to fruits and vegetables was held constant across trials. The relative reinforcing value of palatable snack food in relation to fruits and vegetables was defined as the total amount of points earned for snack food. Two-way analysis of covariance, with hunger and hedonic snack food ratings as covariates, showed that dietary restraint and anxiety had a significant interactive effect on the relative reinforcing value of snack food, indicating that the effect of anxiety on snack food reinforcement is moderated by dietary restraint. Specifically, the high-anxiety/low-restraint women found snack food significantly less reinforcing than low-anxiety/low-restraint women, but no differences emerged between high- and low-anxiety women with high-restraint. Neither restraint nor anxiety had an independent effect on the relative reinforcing value of snack food. These findings indicate that anxiety may have a suppressive effect on the relative reinforcing value of snack food in low-restrained eaters, but not an enhancing effect on snack food reinforcement in high-restrained eaters. Clinical implications of these findings are discussed.

Effects of open-loop feedback on physical activity and television viewing in overweight and obese children: a randomized, controlled trial.

OBJECTIVES: Television viewing and physical inactivity increase the risk of obesity in youth. Thus, identifying new interventions that increase physical activity and reduce television viewing would be helpful in the prevention and treatment of pediatric obesity. This study evaluated the effects of open-loop feedback plus reinforcement versus open-loop feedback alone on physical activity, targeted sedentary behavior, body composition, and energy intake in youth. METHODS: Thirty overweight or obese 8- to 12-year-old children were randomly assigned to an intervention (n = 14) or control group (n = 16). Participants wore accelerometers every day for 8 weeks and attended biweekly meetings to download the activity monitors. For children in the open-loop feedback plus reinforcement (intervention) group, accumulating 400 counts of physical activity on pedometers earned 1 hour of television/VCR/DVD time, which was controlled by a Token TV electronic device. Open-loop feedback control subjects wore activity monitors but had free access to targeted sedentary behavior. RESULTS: Compared with controls, the open-loop feedback plus reinforcement group demonstrated significantly greater increases in daily physical activity counts (+65% vs +16%) and minutes per day of moderate-to-vigorous physical activity (+9.4 vs +0.3) and greater reductions in minutes per day spent in television viewing (-116.1 vs +14.3). The intervention group also showed more favorable changes in body composition, dietary fat intake, and energy intake from snacks compared with controls. Reductions in sedentary behavior were directly related to reductions in BMI, fat intake, snack intake, and snack intake while watching television. CONCLUSIONS: Providing feedback of physical activity in combination with reinforcing physical activity with sedentary behavior is a simple method of modifying the home environment that may play an important role in treating and preventing child obesity.