The primary aim of this research is to determine the efficacy of two portion-control strategies to achieve sustainable dietary and behavior changes and to promote weight loss and maintenance. A randomized controlled trial will test two approaches to managing portion sizes: one that gives individuals skills and tools to help them make appropriate portion choices, and another that focuses on consumption of pre-portioned foods in order to limit exposure to large portions in the personal food environment. A third group will receive a basic nutritional program to promote weight loss.

The second aim of the research is to determine the effects of the programs on knowledge and consumption of appropriate portions, as assessed by innovative assessment methods and multiple-pass dietary recalls. The third aim is to conduct exploratory analyses of individual factors that may influence the response to the portion-control interventions, such as psychosocial indicators, blood biomarkers, and measures of adherence to the interventions. The expected outcome of the project is that it will lead to the development of specific, evidence-based strategies to help control portion sizes in order to manage weight.

Inclusion Criteria:

• Body mass index of 28 to 45 kg/m squared
• Able to safely engage in physical activity (walking)
• Able to attend regular instructional sessions at University Park, Pennsylvania

Exclusion Criteria:

• have a medical condition diagnosed by a physician that precludes participation
• report symptoms indicative of depression or disordered eating
• report serious food allergies or intolerance
• current or planned participation in a weight-loss program
• pregnant or lactating or planning to become pregnant in the next 18 months