Ecological Model for Long-term Weight Control

 

Principal Investigator:  Amy A. Gorin, Ph.D.

The Miram Hospital

 

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. 

Study Visits

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 participantís 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 participantís 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.