NC: Behavior Change Strategies (2007-2008)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

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.
Inclusion Criteria:

The inclusion criteria included:

  • Men
  • Women
  • 25- to 45-year-olds
  • Weight between 14kg and 32kg above insurance industry standards for height and weight
  • Non-smokers
  • Moderate or non-drinkers
  • Individuals on regular diets
  • Individuals not on prescription medications
  • Free from serious medical problems
  • All races.
Exclusion Criteria:
  • Individuals with co-existing illnesses
  • Children.
Description of Study Protocol:


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): 

  1. 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.
  2. 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.
  3. 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.
  4. SBT + Food + Incentives
    • This treatment group included all of the treatment elements described above in combination.
Data Collection Summary:

Timing of Measurements

Interventions lasted 18-months. This study focuses on measures 12 months after the intervention, at 18 and at 30 months.

Dependent Variables

  • 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.

Independent Variables

Behavioral therapy interventions.

Description of Actual Data Sample:
  • 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.

Summary of Results:


SBT Treatment Group

(Mean, CI)

SBT + Food Treatment Group

(Mean, CI)

SBT + Incentives Treatment Group

(Mean, CI)

SBT + Food + Incentives Treatment Group

(Mean, CI)

Control group

(Mean, CI)

Statistical Significance of Group Difference

(Mean, CI)

Body Weight

-1.4kg (7.2)

-2.2kg (6.6)

-1.6kg (5.5)

-1.6kg (6.3)

0.6kg (5.3)


No overall treatment difference between treatment groups in average weight-loss at 30 months, F(4, 157)=0.87, P>0.45.

Other Findings

Orthogonal Contrasts Contrasts Effect Significance
Between-Group Weight-Loss Effect F(4,157)=0.87 P>0.45
All Groups vs. Control Group Weight-Loss Effect F(1,157)=3.14 P<0.08
Between-Group Change in Weight Between 18 and 30 Months F(4,147)=5.94 P<0.0002
Weight Gain in All Treatment vs. Control F(1,147)=17.38 P<0.0001
Weight Gain in Incentive Groups F(1,147)=4.75 P<0.03
Weight Change Between 18 and 30 Months vs. Weight Loss from 0 to 6 Months F(4,136)=0.83 P>0.50
Weight Regain Between 18 and 30 Months vs. Differences in Initial Weight Loss F(1,136)=20.46 P<0.0001

Prediction of Weight Changes: Baseline to 30 Months

Dietary Carbohydrate R=0.20 P<0.01
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.
Author Conclusion:
  • 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.
Funding Source:
Government: NHLBI
Reviewer Comments:
  • 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.