Portion Size Strategies for Management of Body Weight

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 different 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. During a
6-month intervention phase, 300 overweight and obese women will meet biweekly with
dietitians for individual instruction; this will be followed by 6 months of monthly meetings
to promote the maintenance of behavior changes and weight loss. Participants will be
randomly assigned to one of three equally intensive intervention programs. All three groups
will receive basic nutritional and behavioral intervention to promote weight loss. In
addition, the portion-size instruction group will be given training in selecting portions
and in the use of portion control tools such as measuring implements and charts. The
instruction will include an innovative approach based on our previous research, which shows
that consuming larger portions of foods that are low in energy density (such as vegetables
and water- rich foods) enhances satiety and reduces energy intake. A second group of
participants will be provided with pre-portioned foods (such as frozen entrées) for two
meals daily at the beginning of the trial; the frequency of food provision will be reduced
over the course of the intervention phase. Participants will be instructed in other methods
for managing influences on food intake in their personal environment. The third group will
receive the basic nutritional program supplemented with additional information on healthy
eating during weight loss.

It is hypothesized that the two portion-control interventions will result in increased
weight loss during the intervention phase, but that the maintenance of weight loss will
depend on sustained changes in the acquisition and application of portion size knowledge.
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.