Portion Size Strategies for Management of Body Weight

Study Overview
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Brief Summary
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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.

Conditions
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Obesity

Intervention / Treatment
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* Behavioral: Advice on diet, physical activity, and behavior change
* Behavioral: Instruction in food portion size
* Other: Provision of pre-portioned foods
* Behavioral: Advice on healthy eating for weight loss


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Portion size instruction<br>Advice on diet, physical activity, and behavior change. Instruction in food portion size. | Behavioral: Advice on diet, physical activity, and behavior change<br>* Individuals will participate in individual sessions with Registered Dietitians providing basic instruction in principles of weight loss. The program will instruct individuals on the principles of healthy eating and nutrition during calorie restriction. These materials include one module with general information on the importance of limiting portion sizes. The program will also include instruction on physical activity and behavioral strategies for weight loss.<br>Behavioral: Instruction in food portion size<br>* Individuals assigned to this program will participate in individual instructional sessions with specialized materials and tools that address food selection and choosing appropriate portion sizes of various foods.<br>|
| Experimental: Pre-portioned foods<br>Advice on diet, physical activity, and behavior change. Provision of pre-portioned foods. | Behavioral: Advice on diet, physical activity, and behavior change<br>* Individuals will participate in individual sessions with Registered Dietitians providing basic instruction in principles of weight loss. The program will instruct individuals on the principles of healthy eating and nutrition during calorie restriction. These materials include one module with general information on the importance of limiting portion sizes. The program will also include instruction on physical activity and behavioral strategies for weight loss.<br>Other: Provision of pre-portioned foods<br>* Individuals assigned to this program will be provided with commercially available pre-portioned foods and will be taught effective ways to incorporate them into their daily diet.<br>|
| Active Comparator: Comparison<br>Advice on diet, physical activity, and behavior change. Advice on healthy eating for weight loss. | Behavioral: Advice on diet, physical activity, and behavior change<br>* Individuals will participate in individual sessions with Registered Dietitians providing basic instruction in principles of weight loss. The program will instruct individuals on the principles of healthy eating and nutrition during calorie restriction. These materials include one module with general information on the importance of limiting portion sizes. The program will also include instruction on physical activity and behavioral strategies for weight loss.<br>Behavioral: Advice on healthy eating for weight loss<br>* Individuals assigned to this program will participate in individual instructional sessions that address principles of healthy eating while on a calorie-restricted diet.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in body weight | Body weight will be measured at multiple time points during the 12-month trial; the main outcome will be the weight trajectory across this time | Months 0 to 12 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in portion size selection, perception, and knowledge | Computerized assessment of various foods (for self-selected portion sizes, estimation of calorie content, and satiety value) and general knowledge about portion size | Months 0, 3, 6, & 12 | 
| Change in portion size consumption | Portion sizes consumed in various food categories as assessed by diet recalls and diet records | Months 0, 3, 6, & 12 | 
| Change in blood biomarkers | Fasting lipids, glucose, insulin, and calculated insulin resistance | Months 0, 3, 6, & 12 | 
| Change in waist circumference |  | Months 0, 3, 6, & 12 | 
| Change in blood pressure |  | Months 0, 3, 6, & 12 | 
| Change in dietary intakes | Energy intake, nutrient intakes, dietary energy density, food group intakes, and diet quality from three days of 24-hour diet recalls | Months 0, 3, 6, 9, & 12 | 
| Change in step counts | Daily step counts from pedometers | Months 0, 3, 6, 9, & 12 | 
| Change in attitudes and behaviors related to food and eating | Self-reported eating attitudes and behaviors on multiple questionnaires | Months 0, 1, 3, 6, & 12 | 
| Change in psychosocial characteristics | Questionnaires measuring psychosocial characteristics including impulsivity, variety-seeking, and self-efficacy | Months 0, 3, 6, & 12 | 
| Intervention adherence | Number of sessions attended, number of diet and activity records completed, and frequency of using intervention strategies during the entire trial | Month 12 |