NC: Behavior Change Strategies (2007-2008)
The purpose of the study is to evaluate the long-term efficacy of two new behavorial interventions for obesity treatment:
- One using direct reinforcement for weight-loss
- The second using food provision for weight-loss.
The inclusion criteria included:
- 25- to 45-year-olds
- Weight between 14kg and 32kg above insurance industry standards for height and weight
- Moderate or non-drinkers
- Individuals on regular diets
- Individuals not on prescription medications
- Free from serious medical problems
- All races.
- Individuals with co-existing illnesses
101 men and 101 women were recruited through public advertisement in Pittsburgh, Pennsylvania and Minneapolis-St. Paul, Minnesota.
- This study is a randomized controlled trial
- The study participants were randomized by gender and center to one of five experimental groups: A control group, which received no intervention and four intervention groups.
The intervention included four different treatment groups (length of treatment, 18 months):
- Standard Behavorial Therapy (SBT) group
- Participated in counseling sessions once per week for the first 20 weeks and once per month thereafter, with weekly weigh-ins between sessions
- Behavorial counseling included instructions on diet, exercise and behavior-modification techniques
- Dietary goals were assigned at 1,000kcal or 1,500kcal per day, depending on initial body weight
- Exercise recommendations were to walk or bike five days per week, beginning with a weekly goal of 250kcal per week and gradually increasing to 1,000kcal per week
- Participants were asked to keep eating and exercise diaries regularly throughout the program.
- SBT + Food
- The participants were given SBT and also were provided with food each week for 18 months
- Food consisted of pre-measured and packaged dinners and breakfasts for five days per week.
- SBT + Incentives
- The participants in this group were given SBT plus an incentive program, through which each participant could earn financial rewards up to $25 per week for achieving and maintaining weight-loss.
- SBT + Food + Incentives
- This treatment group included all of the treatment elements described above in combination.
Timing of Measurements
Interventions lasted 18-months. This study focuses on measures 12 months after the intervention, at 18 and at 30 months.
- Variable One: Body weight was measured weekly between sessions for the first 20 weeks and monthly thereafter
- Variable Two: Total energy intake and percentage of energy from fat, as assessed by the Block Food Frequency Questionnaire
- Variable Three: Physical activity, as assessed by the Paffenbarger Physical Activity Recall
- Variable Four: Perceived barriers to adherence derived from a 15-question questionnaire
- Variable Five: Nutrition knowledge.
Behavioral therapy interventions.
- Initial N: 202 (101 women and 101 men)
- Attrition (final N): 25 lost to follow-up; 88% completed 30-month follow-up
- Age: 25 to 45 years old with an average age of 37 years
- Ethnicity: 92% were caucasian.
- Individuals were between 14kg and 32kg above insurance industry standards for height and weight
- BMI: 31.
Participants were recruited through advertisements in Pittsburgh, Pennsylvania and Minneapolis-St. Paul, Minnesota.
50% were college-educated.
SBT Treatment Group
SBT + Food Treatment Group
SBT + Incentives Treatment Group
SBT + Food + Incentives Treatment Group
Statistical Significance of Group Difference
No overall treatment difference between treatment groups in average weight-loss at 30 months, F(4, 157)=0.87, P>0.45.
Between-Group Weight-Loss Effect
All Groups vs. Control Group Weight-Loss Effect
Between-Group Change in Weight Between 18 and 30 Months
Weight Gain in All Treatment vs. Control
Weight Gain in Incentive Groups
Weight Change Between 18 and 30 Months vs. Weight Loss from 0 to 6 Months
Weight Regain Between 18 and 30 Months vs. Differences in Initial Weight Loss
Prediction of Weight Changes: Baseline to 30 Months
|Increases in Exercise||R=0.22||P<0.01|
|Reduced Barriers to Adherence||R=0.33||P<0.0001|
|Increases in Nutrition Knowledge||R=-0.21||P<0.01|
- High attenders had greater weight loss: 3.6kg
- Low attenders: 0.7kg.
- The author concluded that maintaining weight loss in obese patients is a difficult and persistent problem. The use of food provision as a component of a behavorial treatment program increased weight loss during the first 18 months of the intervention, but there was no evidence that this strategy improved weight maintenance. Food provision produced greater changes in dietary behavior and greater changes in nutrition knowledge during the initial program, but there was no lasting effect.
- The interventions tested had a reduced frequency of face-to-face counseling after six months. Treatment of any kind was only marginally better than no treatment at all at 30 months
- The results reinforce the idea that increasing initial weight loss is not an effective approach to improving long-term weight outcome
- The strongest predictors of weight loss during the 18-month treatment were changes in dietary fat intake, exercise, perceived barriers to adherence and nutrition knowledge
- The behavior problems in maintenance should be addressed earlier. Programs should develop strategies to help participants maintain their eating and exercise behaviors and to overcome barriers.
- The current study was a well-organized study with clearly stated objectives
- The study period was clearly identified: 18 months of intervention and 12 months of no-treatment follow-up
- The difficulty in maintaining weight loss continues to be a challenge in obesity research. The current study evaluated a variety of different interventions including food provisions and monetary incentives: All treatment groups regained weight
- The questions regarding behavorial changes needed for weight maintenance are still unanswered.