Pediatric Weight Management

Family-based Counseling to Reduce Childhood Overweight (2006)

Citation:

Spieth L, Harnish J, Lenders C, Raezer L, Pereira M, Hangen SJ, Ludwig D. A Low-Glycemic Index Diet in the Treatment of Pediatric Obesity Arch Pediatr Adolesc Med 2000;154:947-951

PubMed ID: 10980801
 
Study Design:
Non-Randomized Controlled Trial
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

The purpose of this study was to evaluate the effects of a low-GI diet in a pediatric outpatient setting. Specifically, we sought to test the hypothesis that a low-GI diet would result in greater weight loss compared with a reduced-fat diet among obese children remaining in outpatient treatment for at least 1 month.

Inclusion Criteria:

Children attending the Optimal Weight for Life Program at Children’s Hospital, Boston, Mass, for treatment of obesity were assigned by the program administrator, based on schedule availability, to 1 of 2 teams.

Exclusion Criteria:

Cushing syndrome, hypothyroidism, hypothalamic disease, diabetes or an obesity-associated genetic syndrome, or those on a very low-energy diet. Also excluded were those individuals who did not complete follow-up  (<1 month) or in complete data.

Description of Study Protocol:

During the period between September 1, 1997 and August 31, 1998, children attending the Optimal Weight for Life Program at Children’s Hospital, Boston, Mass, for treatment of obesity were assigned by the program administrator, based on schedule availability, to 1 of 2 teams, each composed of a subspecialty-trained pediatrician, a dietitian, and at times a pediatric nurse practitioner.

One team prescribed a low-GI diet, the other a reduced-fat diet.  Except for specific dietary recommendations, each team provided similar diagnostic evaluation and treatment.  To estimate the effects of dietary treatment on body fatness, we retrospectively examined the changes in body mass index (BMI [calculated as weight in kilograms divided by the square of height in meters] ) and body weight from the participants initial visit to last visit before December 31, 1998, according to dietary treatment assignment.  The mean changes were adjusted for potential confounding variables as described below.  All patients received a comprehensive medical evaluation, dietary counseling, and lifestyle counseling.  Counseling sessions included the child and at least 1 parent, when possible, according to established practice.  Specific goals were individualized, with consideration given to the patient’s developmental level and readiness to change.  Follow-up appointments generally recommended to occur on a monthly basis for the first four months, and then as needed.

In addition, problem-focused behavior therapy was provided by the program psychologist on an individual basis when referred by a team member.  Within these sessions, a particular nutritional or physical activity goal was identified as a primary treatment target.  A behavioral program was then developed, using positive reinforcement for meeting the specified goal.  Specifics of treatment were adapted according to the patient’s age and developmental stage.

Reduced Glycemic Load Diet

The reduced glycemic load prescription emphasized the selection of carbohydrate containing foods that were characterized by a low to moderate glycemic index. A "Low-GI Pyramid" (modeled on the Food Guide Pyramid) was used as a teaching tool. Diet not energy restricted. Subjects were advised to eat to satiety and snack with hungry. Subjects were told to combine carbohydrate, protein, and fat at each meal or snack. Macronutrient composition prescribed was 45-50% of energy from carbohydrates, and 30-35% of energy from fat. Protein made up the rest of the calories.

Reduced Fat Diet

One team prescribed a standard balanced, hypoenergetic reduced-fat diet because of research demonstrating improvements in adiposity on this diet when combined with behavioral modification and exercise.  The diet followed USDA recommendations for intake of specific food types, as depicted by the Food Guide Pyramid.  Particular emphasis was placed on limiting intake of high-fat, high-sugar, and energy-dense foods, and increasing intake of grain products, vegetables, and fruit.

Physical Activity

Although subjects were counseled on reducing physical inactivity and increasing physical activity, changes in physical activity or inactivity were not reported.

Data Collection Summary:

The primary outcome variables were change in BMI and change in body weight. Height was measured to the nearest 0.1 cm with a wall-mounted stadiometer (Holtrain Ltd., Crymych, England) and weight was measured to the nearest 0.01 kg with an electronic scale (Scaletronix model 6702; Scaletronix Inc., Wheaton, Ill). Changes in BMI and body weight were computed by subtracting the value at the last visit from the value at the first visit.

Recommendations were tailored on an individual basis to incorporate an energy restriction of approximately 1042 kJ (250 kcal) to 2804 kJ (500 kcal) per day compared with usual energy intake.  Specific macronutrient goals were 55% to 60% carbohydrate, 15% to 20% protein, and 30 to 35% fat.

Methods

The primary outcome variables were change in BMI and change in body weight.  Height was measured to the nearest 0.1 cm with a wall-mounted stadiometer (Holtrain Ltd., Crymych, England) and weight was measured to the nearest 0.01 kg with an electronic scale (Scaletronix model 6702; Scaletronix Inc., Wheaton, Ill).  Changes in BMI and body weight were computed by subtracting the value at the last visit from the value at the first visit.

 

Statistical Product and Service Solutions version 9.0 (SPSS Inc., Raleigh NC) software was used for all statistical analyses.  Independent t tests for continuous variables and X2 tests for discrete variables and percentages were used to compare descriptive characteristics of the 2 treatment groups.  General linear regression models were used to compute mean changes in BMI and body weight for the low-GI and reduced-fat treatment groups.  These means were adjusted for potential confounders, including descriptive characteristics, baseline BMI or body weight, follow-up duration, and behavioral therapy referral (see above), using the least squares method.  Statistical significance was defined as P<.05 using 2-tailed tests.  Ninety-five percent confidence intervals were computed to provide an estimate of the precision for the mean changes.  All 2-way interaction terms between dietary treatment and covariates were individually entered into the models to evaluate whether treatment effects might differ according to levels of the covariates.  In addition to the multiple linear regression models, we used subgroup analyses to address potential confounding by difference in behavioral therapy referrals and ethnicity.  As a test of internal validity, we restricted these subgroup analyses to white subjects and to those subjects who did not receive behavioral therapy.  There were too few black and Hispanic subjects to warrant race-specific analyses.  We also performed analyses stratified by tertiles of baseline BMI.

 

Description of Actual Data Sample:

A total of 190 patients were evaluated during the study period. We further excluded 83 individuals for lack of follow-up (<1 month) and/or incomplete data, leaving a cohort of 107.

Summary of Results:

A total of 64 patients received the low glycemic index diet and 43 received the reduced-fat diet for 4.3 vs 4.2 months’ mean duration of follow-up, with a 3.3 vs 3.3 mean number of visits, respectively.

BMI decreased more in the low-GI group compared with the reduced-fat group.  In multivariate models, these differences remained significant after adjustment for age, sex, ethnicity, BMI or baseline weight, participation in behavioral modification sessions, and treatment duration.  Significantly more patients in the low-GI group experienced a decrease in BMI of at least 3kg/m2 vs 1kg/m2.

Mean, age, length of follow-up, number of visits, and sex were similar between the 2 treatment groups.  Baseline BMI and body weight were slightly greater in the reduced-fat group compared with the low-GI group, but the difference was not statistically significant.  Ethnicity differed in the study cohort primarily owing to different follow-up rates (of the 190 patients before exclusion for lack of follow-up, white subjects comprised 71% of 118 individuals assigned to the low-GI group vs. 67% of 72 individuals assigned to the reduced-fat group).  Patients in the low-GI group were somewhat more likely (P=.09) to receive a referral for behavioral therapy than patients in the reduced-fat group.  No adverse events were reported during the study period.

Outcome Differences Between Diets

  • For each BMI tertile, the low-GI group had a significantly larger decrease in BMI than the reduced fat group (P<.02 for each comparision). 
  • Compared with the reduced-fat group, a larger percentage of patients in the low-GI group experienced a decrease in BMI of at least –3 kg/m2 (11 participants [17.2%] vs. 1 participant [2.3%], P=.03). 
  • The overall man change in BMI for the low-GI group was –1.53 kg/m2, compared with =0.06 kg/m2 for the reduced-fat group (P<.001).  This difference remained statistically significant (-1.15 kg/m2 vs. 0.03 kg/m2 , P<.01) after adjusting for age, sex, ethnicity, length of follow-up, baseline BMI, and behavioral therapy referral. 
  • Results were similar for change in body weight after adjustment (-1.16 kg (Low-GI) vs. 1.44 kg (Reduced fat) p<.01).

The authors also obtained similar results when restricting the analyses to those subjects who did not receive behavioral treatment (mean BMI change after adjustment as above: -1.47 kg/m2 for low-GI diet [n=e1] and 0.20 kg/m2 for reduced-fat diet [n=28], p<0.001) and to white subjects (-1.73 kg/m2 for low-GI diet [n=54] and -0.29 kg/m2 for reduce-fat diet [n=23], p<0.01.

Finally, there were no statistically significant interactions between dietary treatment and any of the covariates (data not shown).

Author Conclusion:

A low GI-diet seems to be a promising alternative to standard dietary treatment for obesity in children. Long-term randomized controlled trials of a low-GI diet in the prevention and treatment of obesity are needed.

We believe that these findings are relevant because the magnitude of the observed effect is large and remained significant after adjustment for a variety of potentially confounding factors; the low-GI diet was tested against the current standard of care; and the data are consistent with a plausible physiologic mechanism.  More over, the study reflects experience of a major, clinical pediatric obesity program, not a specialized research protocol employing carefully selected subjects and costly interventions.  Rather, our study confronted a variety of problems inherent to the outpatient treatment of childhood obesity today, including variable motivation and compliance (e.g., some patients enrolled in our program at the insistence of a parent of physician, and have little interest in losing weight), limited resources (ie, inadequate insurance reimbursement), and a lengthy waiting period for clinic appointments.  Thus, the finding speak to the clinical effectiveness of this dietary approach.  Finally, this study underscores the need for a prospective, controlled clinical trial of a low-GI diet in the treatment of obesity.

Funding Source:
Government: NIDDK
University/Hospital: Children's Hospital
Not-for-profit
0
Foundation associated with industry:
Reviewer Comments:

Study groups not well-described. Reasons for withdrawal not discussed. Follow-up period was short. Lacked an intent to treat analysis.

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
  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
  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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? 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
  2.1. 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
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? 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
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  3. Were study groups comparable? No
3. Were study groups comparable? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) 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
  3.2. 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.) No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) No
  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? 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? Yes
  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.) N/A
  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.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
  4. Was method of handling withdrawals described? No
4. Was method of handling withdrawals described? No
  4.1. Were follow-up methods described and the same for all groups? No
  4.1. Were follow-up methods described and the same for all groups? No
  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%.) No
  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%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  4.4. 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? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  5. Was blinding used to prevent introduction of bias? No
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
  5.1. 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
  5.2. 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? No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? No
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
  6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
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
  6.1. 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? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? No
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? No
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments 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
  6.7. 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? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
  7. Were outcomes clearly defined and the measurements valid and reliable? Yes
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? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  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? No
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? No
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
  8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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
  8.5. 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
  8.6. 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? No
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
  9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes