Ecological Model for Long-term Weight Control
Principal Investigator: Amy A. Gorin, Ph.D.
The
Abstract:
The
obesity epidemic observed in recent years can be largely attributed to an obesogenic environment that encourages overeating and sedentary
lifestyles. Behavioral weight control treatment, the most empirically validated
intervention approach, produces initial weight losses of 10%; however,
maintenance of initial weight loss and behavior change has not been achieved. These disappointing long-term results may
reflect the fact that participants are given only minimal, indirect instruction
on how to change their environment to support their new weight-regulating
behaviors. While in theory, the behavioral model emphasizes environmental antecedents
and consequences of eating and exercise, in practice, only 1 to 2 sessions in
standard treatment are dedicated to stimulus control-types of skills. By teaching weight control skills in a
contextual vacuum, participants remain vulnerable to the same environmental
influences that maintained their unhealthy eating and exercise habits. Given
that the majority of eating and exercise is home-based, a logical step in
strengthening behavioral treatment and moving toward an ecological model of
behavior is to expand the focus of treatment from the individual to the
individual plus their home environment. We propose to test the long-term impact
of a behavioral weight control program designed to directly modify both the
physical and social home environment of weight loss participants. Two hundred
overweight and obese men and women will be randomly assigned to either 24
months of standard behavioral treatment (SBT) or 24 months of standard
behavioral treatment plus direct modifications to the home environment (SBT+Home). SBT+Home will incorporate many strategies that have shown
promise in improving weight loss (e.g., food and exercise equipment provision,
spouse involvement) but will be the first to study both physical and social
factors within the home simultaneously and will be the longest examination of
the home environment conducted to date.
Participants and spouses will be assessed at baseline, 6, 12, 18, and 24
months. We hypothesize that by broadening the focus of treatment from the
individual to the individual plus their home environment, SBT+Home
will produce both better long-term weight loss and better maintenance of
initial weight loss and behavior change. This home environmental approach, if
successful, has potential applications to the maintenance of other important
health behaviors.
Specific Aims:
The
United States is in the midst of an obesity epidemic, a problem brought on
largely by an obesogenic environment that encourages
overeating and sedentary lifestyles.43,50,51,125 Behavioral weight control treatment, the most
empirically validated intervention approach for obesity, produces initial
weight losses of 10%;132,139,142 however, changes in eating and
exercise are not maintained and nearly all weight is regained within 3 to 5
years.45,107 One possible
explanation for these disappointing long-term results is that behavioral weight
control treatment provides only minimal, indirect instruction on how to modify
the environment to support behavior change.62 While in theory, the behavioral model emphasizes
environmental antecedents and consequences of eating and exercise;7
in practice, only 1 to 2 sessions in a standard 6 month program are dedicated
to stimulus control-types of skills. By teaching weight control skills in a contextual vacuum, current behavioral programs leave
participants vulnerable to the same environmental influences that supported
their unhealthy eating and exercise habits.
Initial motivation to lose weight and frequent contact with
the intervention staff at the start of treatment may temporarily counteract
these environmental pressures; however, over time, these influences may make
maintaining weight-regulating behaviors, and consequently long-term weight
loss, impossible.
We have evidence from our prior studies, and from the existing
literature, that directly modifying the home environment improves weight loss. The home is
an important setting for intervention because the majority of meals and snacks
are consumed in the home,10 a large percentage of both physical and
sedentary activity is home-based,114 and factors within the home are
known to affect eating and exercise.24,59 Strategies modifying the home environment
(e.g., food provision, provision of exercise equipment) have produced better
overall weight loss for up to 18 months;11,60,69 however a closer
examination of the trajectory of weight change from 6 months on suggests that
in nearly all studies, regain occurs at the same rate as in standard behavioral
treatment. To date, investigations of the home environment have targeted a
single aspect physical (provision of food or exercise equipment) or social
(spouse support) aspect of the home.
Given the synergy between physical and social factors within the home
(e.g., food provision is unlikely to work if other family members are bringing
tempting foods into the home), a logical step for improving these manipulations
is to develop a behavioral program that targets multiple factors within the
home simultaneously to capitalize on the cumulative effects of a comprehensive
approach.
The primary aim of the proposed study is to examine the long-term
efficacy of the first behavioral weight control program to directly modify both
the physical and social home environment of weight loss participants. Two
hundred overweight and obese men and women will be randomly assigned to either
24 months of standard behavioral treatment (SBT) or 24 months of standard
behavioral treatment plus direct modifications to the home environment (SBT+Home).
Participants and spouses will be assessed at baseline, 6, 12, 18, and 24
months.
The
primary hypotheses to be tested are:
1a. SBT+Home, by creating a microenvironment that supports
healthy eating and exercise,
will
produce significantly greater weight losses than SBT at the end of the 24-month
treatment period.
1b. SBT+Home will result in better maintenance of initial weight
loss (less regain) from 6 to 24 months
than SBT.
The secondary aims of the proposed study are:
2.
To compare SBT
and SBT+Home at 0, 6, 12, 18, and 24 months on the
following variables:
a.
The physical
home environment defined as the amount of low- and high-fat foods in the
home, the number of low- and high-fat foods on display in the home, the amount
of exercise equipment in the home, and the number of television sets in the
home; and the social home environment defined as the amount of
support provided by spouses and the eating, exercise, and sedentary behaviors
of spouses.
b.
Dietary intake
(total calories consumed, percentage of calories consumed from fat), physical
activity (calories expended), and sedentary activity (number of hours of
TV/week).
c.
Marital
functioning and depression.
d.
Treatment
adherence.
3.
To examine
whether changes in the variables defined above (2a-c) are related to changes in
weight.
4.
To examine
whether changes in dietary and activity patterns mediate the relationship
between the home environment and weight change.
5.
To investigate
the effect of spouse involvement on weight loss in the SBT+Home
condition by a) examining the covariation in change
in weight, dietary intake, and physical activity between participants and
spouses; b) determining whether the intervention is equally effective for
participants and spouses; and 3) determining the characteristics and behaviors
of spouses that are associated with the greatest success in weight loss at 24
months for participants.
The
proposed study will provide important information about long-term weight
control and is innovative for several reasons: 1) By broadening the focus of
weight loss treatment from an individual-level intervention (participant only)
to a multi-level intervention (participant plus their home environment),
the proposed intervention strengthens behavioral treatment and moves toward an
ecological models of health promotion; 2) The control group (SBT) incorporates
state-of-the-art knowledge about factors promoting maintenance (e.g., extending
face-to-face treatment for 2 years; prescribing a higher exercise goal) to
provide the best test of long-term efficacy; 3) The 24 month assessment and
treatment period is consistent with a chronic disease model of obesity and will
be the longest examination of the impact of home environmental manipulations on
eating and exercise conducted to date ; and 5) Because of its multi-faceted
approach (physical and social factors simultaneously addressed) and its use of
strategies currently available to the public at large (television monitoring
devices and home food delivery ordered via the internet), SBT+Home
will be the most powerful and sustainable home environment weight loss
treatment program ever tested. This home environmental approach, if
successful, has potential applications to the long-term management of several
health problems including alcohol and drug use and other high-risk
behaviors.
Screening
Visits. Individuals who
contact the clinic in response to advertisements will be given a brief
description of the study and will complete a telephone screening to determine
initial eligibility. The marital partner
(husband or wife) who responds to the advertisement will be identified as the
participant. Eligible participants and their spouses will be asked to attend an
orientation at the clinic, at which time the study will be described in more
detail, informed consent will be obtained, and a baseline assessment visit will
be scheduled for the couple. This
baseline visit will be conducted at the participant’s home to obtain objective
information about the physical home environment. Participants who complete the baseline
assessment will be randomized to either SBT or SBT+Home.
Follow-up Visits. Participants
and spouses in both conditions will complete follow-up visits at 6, 12, 18, and
24 months. At 6 and 24 months, these
assessments will be completed at the participant’s home, while at 12 and 18
months, these assessments will be completed at the clinic. Research assistants, blinded to group
assignment, will conduct all assessments.