Pediatric Weight Management

PWM: Physical Activity and Inactivity (2006)


Epstein LH, Paluch RA, and Raynor HA. Sex Differences in Obese Children and Siblings in Family-based Obesity Treatment. Obesity Research 2001;9:746-753


PubMed ID: 11743058
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

The goal was to evaluate sex differences in child weight control programs that are targeted increasing physical activity (increase) or the combination of reducing sedentary behavior and increasing physical activity (combined).

A second goal was to evaluate the benefits of family-based interventions on nontargeted siblings.

Inclusion Criteria:
  1. child at or above 85th body mass index (BMI) percentile for age and sex and less than 100% over the average BMI for age and sex;
  2. child between 8 and 12 years of age;
  3. neither parent over 100% overweight;
  4. one parent willing to attend weekly treatment meetings;
  5. neither parent or child on an alternative weight-control program; and
  6. no medical restrictions on the participating parent or child that would prevent exercise, no current psychiatric disorders in parents or children,
  7. no history of eating disorders in parents
Exclusion Criteria:

One family was excluded from the analyses after a severe accident. One father was dropped from analysis because he entered another weight-control program.  One mother was dropped from analysis after she became pregnant, and eight families did not provide complete 6-and 12-month follow-up data.  The data that were excluded included five children in the increase activity group (one boy and four girls) and six children in the combined group (three boys and three girls).

Description of Study Protocol:

The treatment program included 16 weekly meetings, followed by 2 biweekly meetings and 2 monthly meetings during the 6-month intensive treatment, and a 12-month follow-up. Families received parent and child family-based, weight-control workbooks, which included five main sections:

  1. introduction to weight control and self-monitoring
  2. the Traffic Light Diet
  3. the specific activity program
  4. behavior change techniques
  5. maintenance of behavior change. 

Each participating family member was weighed each week, and at the weigh-in, behaviors related to weight loss were probed and their weights graphed on group graphs to provide feedback on progress.  The meeting structure was set up so that families met with an individual therapist for 30 minutes the first week, and on subsequent weeks they alternated between attending separate child and parent 30-minute group meetings and individual meetings with a therapist.  During individual meetings therapists reviewed weekly weight change and discussed subject’s perception of behavior change related to weight change and reviewed several days of each habit book, followed by a review of progress toward contract and provision of reinforcers.                  

All participants were provided information about diet and behavior change techniques, with the primary differences among groups regarding the ways to increase activity.  The Traffic Light Diet was used to decrease energy intake and promote a balanced diet.  With this diet plan, foods are categorized as red, yellow, or green on the bass of their energy and nutrient content.  Green foods are very low in calories with high nutrient density.  Yellow foods are higher in calories and include the dietary staples needed for a balanced diet.  Red foods are higher in calories with low nutrient density.  While they were attempting to lose weight, children and overweight parents were instructed to consume between 1200 and 1500 kcal/d, to limit red foods to 10 or les per week, and to maintain nutrient balance by eating the recommended servings based on the food guide pyramid.  When participants got below the obesity criterion, they were provided instructions in developing a maintenance calorie level, which involved gradually increasing energy intake in 100-kcal/d increments on a weekly basis until weight gain occurred.  Non-overweight parents had no caloric restriction but were asked to limit red foods to 10 or fewer per week.  Families were provided information in regard to reading food labels, shopping, and current findings in research on obesity and nutrition.

Parents and children were taught positive reinforcement techniques to increase behaviors that included praise and reciprocal contracts in which parents and children set goals and determined reinforcers to be provided by the parent based on meeting the goal.  In addition, parents deposited $75.00, which was returned contingent on completing 75% of the treatment sessions and attendance at the 6-and 12-month follow-up.  Families were taught stimulus control to reduce access to high-calorie foods.  Preplanning was used to facilitate decision making and problem solving when difficult eating and activity situations could be anticipated, such as praise, holiday gatherings, and school or work functions. 

In addition to information that focused on changes in targeted children, parents were also informed of methods to change health  habits of all family members, along with handouts for siblings, relatives, and friends

Data Collection Summary:

Height was measured in 0.125-inch intervals either using a lab-constructed board or a standiometer, and weight was measured in 0.25-pound intervals using a balance beam scale. Children and parents who were greater than 85th BMI percentile were considered obese.  Percentage of overweight calculations were based on comparisons of the participant BMI to the 50th BMI percentile for age and sex using standards derived from the National Health and Nutrition Examinations Survey III.

Child and parent BMI’s were calculated at baseline and at 6 and 12 months.  Self-reported data were used when individuals were unable to attend the assessment.  Due to underestimation of weight and overestimation of height, all self-reported data were adjusted for height and weight self-report based on a dataset of over 1000 cases in which adult and child heights and weights were self-reported and then measured.  Self-report data accounted for 7.3% of the observations.

Description of Actual Data Sample:

Sixty-seven families with obese children and 89 siblings.

Summary of Results:

At 12 months, boys showed significantly better percentages of overweight changes (-15.8%) for the combined treatment than girls (-1.0%), with no significant differences for the increase intervention for boys (-9.3%) or girls (-7.6%). Boys adhered to treatment better than girls.  Adherence and predilection for physical activity were significant predictors of targeted sibling weight loss which included age, number of siblings, targeted child percentage of overweight change, and the interaction of group assignment by same sex of treated sibling.

There was a significant interaction of group by sex in the rate of change in percentage of  overweight (F2,102 ) = 5.16, p = 0.007, ES = 0.25) as well as a significant effect of sex on the rate of change (F (2,120) = 8.30, p< 0.001, ES = 0.31) and a significant effect of time (F (2,102) 5.52, p< 0.005, ES = 0.87).  As shown in Figure 1, the interaction of group by sex was due to boys in the combined group showing larger reductions in percentage of overweight than girls in the combined group (F (2, 50) = 8.98, p< 0.001), or in the increase activity group (F (2, 50) = 4.45, p< 0.025).  The sex effect was due to boys showing larger reductions than girls. 

At 1 year, boys showed a decrease in BMI –1.76 ± 1.86 for the combined group and 0.65 ± 1.37 in the increase activity group.  Girls showed a BMI increase of 1.00 ± 1.73 for the combined group and a decrease of 0.27 ± 1.37 in the increase activity group.  A significant effect of sex was observed for child and parent adherence to treatment, with boys (3.25 ± 0.73) and parents of boys (3.03 ± 0.49) significantly (F(1,52) = 12.17; p< 0.001) more adherent than girls (2.78 ± 0.62) and targeted parents of girls (2.69 ± 0.45). 

A significant interaction of group by time was observed for friend encouragement to make healthy behavior changes, with decreases observed for children in the activity group (- 1.57 ± 2.71) and no change (0.21 ± 3.71) for children in the combined group.  No other significant changes over time or interaction of change by group were observed for family support.

Several baseline and change over 1-year variables were significantly (p < 0.05) related to changes in targeted child percentage of overweight.  The best fitting multiple regression model to predict changes in percentage of overweight over the year is shown in the top of Table 3, including predictors of weight change of adherence (better adherence, better weight change) and predilection (higher predilection, better weight change) for physical activity.  Although child sex was not an independent predictor when adherence and predilection were considered in the model, this may be because child sex was related to predilection for physical activity (r = 0.31, p< 0.021), with boys having greater predilection scores (34.2 ± 3.6) than girls (31.0 ± 6.2), and to adherence to treatment as previously presented.

The best fitting model predicting sibling change included age (older have better weight change), number of siblings (more siblings better weight change), targeted child weight change (larger changes in targeted child, better sibling weight change), group, same sex as the targeted child, and the interaction of group by same sex as the targeted child.  The largest decrease was if the child was the same sex as the targeted child and in the combined group, which was significantly greater than changes for same sex sibling in the active group (F(1,83) = 4.91; p=0.03).  Of the 18 same sex siblings in the combined group, 9 were boys and 9 were girls.  The girls showed an average increase in percentage of overweight of 1.0 ± 9.9, whereas the boys showed an average decrease in percentage of overweight of –5.6 ± 8.6, consistent with the direction of change of the targeted children.  BMI changes for same sex siblings in the combined group were a decrease of 0.03 ±1.46, whereas opposite sex siblings in that group increased their BMI by 0.87 ± 1.76.  Same sex siblings in the increase activity group increased their BMI by 0.94 ± 0.94, whereas opposite sex siblings increase BMI by 0.33 ± 1.49.  The influence of being younger or older than the targeted sibling was strongly related to sibling age and not an independent predictor when sibling age was included in the model.

Author Conclusion:

Sex may influence response to obesity treatment programs that focus on the combination of reducing sedentary behaviors and increasing physical activity to increase energy expenditure and reduce opportunities to eat.

Girls may not respond as well as boys to the combined treatment but may respond equally as well to interventions that provide a diet and target increases in physical activity. 

The sibling results suggest that there is some generalization to siblings, with larger effects for same sex siblings and for older siblings, but given the the relatively small changes in siblings, it may be necessary to increase reinforcement for behavior change to siblings of the targeted child or to provide treatment at the family level for all obese siblings, taking advantage of changes in the environment and changes in parenting that accompany treatment, but targeting multiple children in the family.  Because obesity runs in families, development of treatments that target multiple family members may provide unique benefits for family-based obesity treatment.

Funding Source:
Reviewer Comments:


Not clear if self-report height and weight were used in the analysis and if so, which subjects – from what group.

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? ???
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) ???
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? ???
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? ???
5. Was blinding used to prevent introduction of bias? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? ???
  5.5. In diagnostic study, were test results blinded to patient history and other test results? ???
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? ???
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? ???
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? ???
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? ???
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? No
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes