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A behavioral economic analysis of changes in food-related and food-free reinforcement during weight loss treatment.

OBJECTIVE
Behavioral economic theory predicts that reductions in consumption of highly valued commodities, such as drugs or palatable food items, are facilitated by increasing engagement in reinforcing substitutes. The current study prospectively examines changes in engagement in and enjoyment of food versus food-free activities during an 18-month behavioral weight loss intervention.


METHOD
Participants were 202 overweight/obese individuals who took part in an 18-month behavioral weight loss treatment and were randomly assigned to a traditional hypocaloric, low-fat diet condition or a traditional hypocaloric, low-fat diet plus a goal to limit variety in snack food consumption condition. At baseline and 6, 12, and 18 months, participants were weighed and completed a measure that assessed recent frequency of engagement in and enjoyment of a variety of both food and food-free activities.


RESULTS
Growth models revealed a statistically significant decrease in the relative percentage of food-related reinforcement (vs. food-free) over time (reinforcement ratio, or RR), with the greatest reduction during the first 6 months of treatment. Food-related reinforcement decreased over time, and food-free reinforcement increased. Additionally, the RR change predicted change in body mass index (BMI) from 0 to 6 months and 0 to 18 months, such that greater changes in RR were associated with greater changes in BMI.


CONCLUSIONS
Findings suggest that behavioral weight loss treatment may promote a shift away from food-related reinforcement toward food-free reinforcement and that this change may predict BMI change. Future interventions may consider targeting increasing engagement in enjoyable food-free activities to help with long-term maintenance.