Pediatric Weight Management

PWM: Individual Child Counseling (2006)

Citation:

Sondike SB, Copperman N, Jacobson MS. Effects of a low-carbohydrate diet on weight loss and cardiovascular risk factor in overweight adolescents. J Pediatr 2003; 142: 253-8.

PubMed ID: 12640371
 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To compare the effects of a Low-Carbohydrate (LC) diet with self-selected energy intake to a Low-Fat (LF) diet with self-selected energy intake on weight loss in overweight adolescents and to examine the effects of these diets on serum lipids.

The authors hypothesized that:

  1. An energy-unrestricted, very-LC diet without restriction of fats would result in more weight loss compared with a LF diet over a 12-week period.
  2. This diet would increase cardiovascular risk as assessed by serum lipid profile.
Inclusion Criteria:

Participants were recruited from patients 12 – 18 years of age who were referred to the Center for Atherosclerosis Prevention of Schneider Children’s Hospital by their pediatricians for weight management. Patients who had primary obesity with a BMI > 95th percentile for age (reference data = NCHS CDC) were screened and referred for random assignment.

Exclusion Criteria:

Patients were excluded from participation if they exhibited any of the following:

  • any chronic disease affecting growth
  • diabetes mellitus
  • familial hypercholesterolemia
  • clinically diagnosed psychological disorders
  • any chronic disease medication use
  • abnormal thyroid, kidney, of liver function tests,
  • abnormalities in the complete blood count
Description of Study Protocol:

LC group was prescribed a diet that consisted of a daily intake of no more than 20 g/d of carbohydrate and ad lib intake of protein, fat, and energy for the initial 2 weeks. For week 3 through 12, carbohydrate was increased to 40 g daily by adding additional nuts, fruits, and whole grains. Participants were advised to consume a minimum fluid intake of 50 oz/d, a multivitamin supplement (100% RDA for age), and potassium chloride table salt substitute. Fiber supplements were prescribed when symptoms of constipation occurred.

LF group was instructed to eat a diet consisting of <40g/d of fat, with 5 servings of starch per day and ad libitum intake of fat-free dairy foods, fruits and vegetables for 12 weeks. Juice and sweetened beverages were omitted from the meal plan. A multivitamin (100% RDA for age) was recommended.

Both diets shared a “stoplight” meal plan design with 3 categories of foods (as suggested by Epstein & Squires 1988). 30 minutes of aerobic exercise 3 times per week was recommended to both groups of adolescents.

Statistical Analysis

Kruskal-Wallace nonparametric tests were used to compare pre-intervention and post-intervention weight, BMI & BMI Z-scores.

Data Collection Summary:

Dependent

  • Baseline and bi-weekly weights & BMI (measured using standardized methods);
  • Baseline and 12-week fasting total cholesterol, triglyceride levels, HDL cholesterol levels, calculated LDL & non-HDL-C, glucose, urea nitrogen, creatinine, urea nitrogen/creatinine ratio, total protein, albumin, total bilirubin, alkaline phosphatase, AST, ALT & electrolyte levels;
  • Dietary Adherence (monitored by RD); Dietary intake – Energy, Fat, Carbohydrate, Protein, Cholesterol, Saturated, Monounsaturated & polyunsaturated fatty acids (3-day food records).

Independent

  • LC diet group or LF diet group (see Study Protocol).

Control Variables

  • Age 
  • Sex
Description of Actual Data Sample:

Original Sample: 39 patients were enrolled and randomly assigned into 2 diet treatment groups (LC diet group, n=20 & LF diet group, n=19).

Withdrawals/Drop-Outs: Participants who failed to complete at least 4 successive visits were excluded from final analysis and were reported as dropouts.

Final Sample: 30 patients (77% of the original sample) who reported compliance with the prescribed diet and completed at least 8 of the 12 weeks of the study period (LC = 16, LF =14).

Location: New York City suburban area.

Race/Ethnicity: not reported

SES: not reported

Summary of Results:

No significance differences were detected between the groups on any of the baseline measurements. The dropout rate did not differ significantly between groups (LC: 4 of 20, LF: 5 of 19).

Weight Loss

Of those considered for final analysis, adolescents in the LC group lost 9.9±9.3 kg compared with 4.1±4.9 kg for teens in the LF group (P<0.04).

8 of 16 subjects in the LC group lost more than 1 kg/wk compared with 4 of 14 in the LF group (P<0.05).

BMI

The average BMI improvement noted at the end of the 12-week trial was significantly better in the LC group compared with the LF group (3.3±3.0 kg/m2 vs 1.5±1.7, P<0.05).

Analysis of weight differences with BMI T-scores used to adjust for age and sex showed a significantly greater change in the LC group than in the LF group (P=0.04).

Dietary Intake

On average, participants in the LC group reported consuming more energy compared with those in the LF group (P < 0.03).

The LC group ate more saturated fat and more cholesterol than the LF group (P<0.0001).

Lipid Parameters

Participants in the LF group realized a significant decrease in LDL-C, whereas those adolescents in LC group did not.

Serum Triglyceride values decreased significantly from baseline in the LC group.

Of greatest importance for both groups, none of the lipid parameters measured worsened significantly.

Author Conclusion:

These data suggest that adolescents randomly assigned to a LC diet were more likely to have greater weight loss over a 12-week period than teens treated on a LF diet and that the LC group lost more weight despite a higher reported energy intake.

Contrary to the authors’ hypothesis, the LC diet did not appear to harm their lipid profile over a 12-week period.

Funding Source:
University/Hospital: Schneider Children's Hospital
Reviewer Comments:

Strengths

  • Good dietary compliance.

Limitations

  • Differential underreporting can neither be confirmed nor denied from the data.
  • Exercise was not documented.
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) N/A
  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) N/A
 
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? ???
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? ???
  1.3. Were the target population and setting specified? ???
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? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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? 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
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? Yes
  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
  5.1. 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? 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
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? N/A
  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? N/A
  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
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
  7.2. 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? 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
  8.2. 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? N/A
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