Obesity Reduction Black Intervention Trial (ORBIT)
- To estimate the effectiveness of a 24-week diet and physical activity intervention and
a 1-year maintenance intervention designed to produce and maintain weight loss in obese
- To estimate the effect of these interventions on changes in fasting serum insulin,
glucose, and free IGF-1, IGFBP-1, and IGFBP-2 levels as well as total IGF-1 and IGFBP-3
- To compare changes in dietary consumption of total calories, total fat, fruits,
vegetables, and fiber as well as physical activity in participants undergoing a
weight-loss intervention vs a control intervention.
- To compare changes in knowledge, attitudes, self-efficacy, and social support related
to diet, physical activity, and weight loss in participants undergoing a weight-loss
intervention vs a control intervention.
- Assess the efficacy of a weight-loss intervention mechanism and the association between
weight loss and weight loss maintenance with potential biologic mediators of breast
OUTLINE: Participants are randomized to 1 of 2 intervention arms.
- Arm I (weight-loss intervention): Participants undergo a combined weight-loss
intervention (diet and physical activity) over 24 weeks comprising individualized
sessions with an interventionist once monthly and group sessions twice weekly. During
the group sessions, participants receive information about diet, physical activity, and
weight loss and take part in exercise classes. Participants receive handouts,
food-measuring tools, and pedometers. Participants also discuss goal setting and
problem solving. During the individualized sessions, participants undergo motivational
interviewing (MI) to assess their individual needs and to motivate them to make or
sustain behavioral changes.
Beginning 1 month after completion of the combined weight-loss intervention, participants
undergo a weight-loss maintenance intervention over 12 months. Participants continue their
exercise classes twice weekly and receive a copy of the aerobic exercise class videotape for
use at home. Prior to each exercise session, participants may share their weight-loss
experiences (e.g., successes, struggles) or a motivational or informational story, article,
or prayer with other group members. Participants also receive weekly newsletters that
include information presented in the original weight-loss intervention, opportunities in the
community for physical activity (e.g., ice skating, swimming, or local walks), and further
advice on maintaining weight loss. Participants undergo 4 MI sessions over the telephone
that address diet, physical activity, and weight-loss maintenance strategies. The MI
sessions also provide an opportunity for individualized problem solving.
- Arm II (control intervention): Participants undergo a control intervention over 24
weeks comprising weekly newsletters on general health topics, such as first aid,
smoking cessation, cancer screening, and disease prevention, and monthly general health
classes that demonstrate information conveyed in the newsletter (e.g., first-aid
After completion of the control intervention, participants undergo a control maintenance
intervention over 12 months comprising a monthly newsletter on general health topics. After
completion of the maintenance intervention, participants undergo 10 intervention sessions
and receive the same study-related materials (handouts, food-measuring tools, and
pedometers) as in arm I.
Blood samples are collected at baseline, 24 weeks, and 18 months for laboratory biomarker
studies. Samples are analyzed for insulin levels by radioimmunoassay, glucose
concentrations, and total and free IGF-1, IGFBP-1, IGFBP-2, and IGFBP-3 by enzyme-linked
Participants complete questionnaires at baseline, 24 weeks, and 18 months to assess diet,
physical activity, cognitive measures (attitudes, beliefs, and self-efficacy), social
support, and environmental measures.
Body mass index as assessed at baseline, 24 weeks, and 18 months
Marian Fitzgibbon, PhD
University of Illinois
United States: Federal Government
|University of Illinois Cancer Center||Chicago, Illinois 60612-7243|