PWM: Physical Activity and Inactivity (2006)


Becque MD, Katch V, Rocchini A, Marks C, and Moorehead C. Coronanry Risk Incidence of Obese Adolescents: Reduction by Exercise Plus Diet Intervention/ Pediatrics 1988;81;605-12.

PubMed ID: 3357722
Study Design:
Randomized Controlled Trial
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Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

A group of obese adolescents was examined to determine the incidence of coronary heart disease risk factors and the effects of a 20-week diet and exercise intervention program.

Inclusion Criteria:

Body weight and triceps skinfold greater than the 75th percentile for age and sex.

Exclusion Criteria:
None cited
Description of Study Protocol:

The adolescents were randomly assigned to either a control, diet therapy and behavior change, or exercise, diet therapy, and behavior change group.

Control adolescents were encouraged not to change their basic life-style. A postintervention questionnaire was used to verify the lack of behavioral change.

The diet plus behavior change subjects met with a dietitian and behavior therapist once a week for 20 weeks.  A program of moderate dietary restriction was based on the ADA exchange program.  Caloric intake was set to elicit the loss of 1 to 2 lbs per week.  Continual follow-up and adjustment of eating patterns and caloric intake were done weekly by the nutritionist.  Weekly food record were kept and rewards given by compliance.  In addition, nutrition education materials were prepared weekly.  Behavioral treatment included four main elements: record keeping, stimulus controlling to restrict the external cues that set the occasion for eating, changing the topography of eating, and reinforcing of altered behavior.  Stimulus control procedures centered around the identification and eventual manipulation of the cues responsible for inappropriate food intake.  Reinforcement techniques included both contingency management and self-reinforcement.

The exercise plus diet behavior change group’s diet and behavior therapy program was the same as above.  The exercise program was conducted 3 times per week for 50 minutes.  Each session included warm-up/flexibility exercise and aerobic activity.  Aerobic exercise that involved movement of the total body weight to ensure maximum caloric expenditure were emphasized.  The intensity of exercise was monitored by heart rate.  The duration of aerobic exercise for the first 2 weeks was 15 minutes.  Exercise duration was progressively increased by 5 minutes each week so that by week 7 to 8 subjects were completing 40 minutes per session.

Data Collection Summary:

Height was measured to the nearest 0.1cm with a standard stadiometer, body weight to the nearest .01 kg, and total body weight to the nearest.o1kg. Residual lung volume was determined prior to immersion by the oxygen dilution technique in the same bent-forward position as was used for underwater weighing.  % of body fat was calculated from body density.  Fat weight was calculated from % fat, and lean body weight was calculated by subtraction. 

Maximum oxygen uptake was determined during a discontinuous bicycle ergometer stress test.  Oxygen and carbon dioxide concentrations were measured from mixed expired gas with Beckman OM-11 and Instrumentation Laboratory End-Tidal 2000 analyzers, respectively.  Expired volumes were determined with pneumotachograph connected to a a pressure transducer, integrator, and demodulator.  The cycle test started at 0 W and the resistance was increased by 50 W every three minutes.  After each work load the subject rested for four minutes. The cycle test was terminated when the subject could no longer complete a 3-minute exercise stage.  Oxygen uptake was calculated by standard procedures and expressed in standard temp and pressure dry units.

A butterfly needle was inserted into an antecubital vein and 10 mL of blood was drawn from each adolescent.  Cholesterol was spectrophotometrically determined on a computer-directed analyzer using the Manheim enzymatic method.  High-density lipoprotein-cholesterol level was determined after a combination of dextran sulfate and magnesium chloride was used to precipitate the very low-density lipoproteins from the plasma.  Triglyceride levels were spectrophotometrically determined on a computer-directed analyzer using Calbiochem-Behring enzymatic triglyceride reagents in which lipase was used to hydrolyze triglycerides.

Systolic and diastolic BPs were determined after the adolescents had been resting in a reclined position for 20 minutes.  A Critikon exercise monitor model 1165 automated blood pressure machine was used for all BP measurements.

Description of Actual Data Sample:

36 obese adolescents

Summary of Results:

A significant (P< .05) group-by-time interaction was found for systolic BP z scores, diastolic BP z scores, and high-density lipoprotein-cholesterol levels. Although triglyceride levels, total cholesterol level, percentage of fat, and maximum oxygen uptake did not exhibit significant group-by-time interactions, the percentage changes from pre- to post-treatment were noteworthy.  In the control group, triglyceride levels increased 3.8%, whereas in the diet/behavior change and exercise/diet/behavior change groups triglyceride levels decreased 32.5% and 14.8%, respectively.  Similarly, maximum oxygen uptake decreased 2.9% in the control group, but increased 0.5% in the diet/behavior change group and 2.2% in the exercise/diet/behavior change group.  Total cholesterol levels decreased in all groups, yet the change in the exercise/diet/behavior change group (12.5%) was twofold greater than that of either the control (5.5%) or diet/behavior change (5.1%) groups.

The total number of risk factors both pre- and post-treatment can be calculated for each group by summation of the subjects’ risk factors.  Seven modifiable risk factors were identified for this analysis; total cholesterol levels, triglyceride levels, high-density lipoprotein-cholesterol levels, systolic BP z scores, diastolic BP z scores, obesity and physical work capacity.  For example, it is possible for the 14 control subjects to have 98 (14 x 7 = 98) total risk factors.  A reduction of all risk factors to less than the respective cutoff value would reduce the group’s total risk factors to zero.  Therefore, the percentage change in multiple risk incidence for each group can be calculated with the knowledge of the change in the total number of risk factors from pre- to post-treatment.

A reduction of eight risk factors from pre- to post-treatment was found for the control group (five participants reducing one risk factor; one subject reducing two risk factors; and one participant reducing three risk factors; two participants increased one risk factor).  This is a 10.3% reduction in total risk.   Likewise, a reduction of nine risk factors pre- to post-treatment was observed for the diet plus behavior change group (five participants reducing one risk factor and two participants reducing two risk factors).  This is a 1.48% reduction in total risk.  In contrast, a reduction of 24 risk factors was observed for the exercise/diet/behavior change group (two participants reducing one risk factor; three participants reducing two risk factors; and four participants reducing four risk factors).  This is a 41.4% reduction in total risk.

Thus, a change of 2.18 risk factors per adolescent was noted for the exercise/diet/behavior change group.  On the other hand, an average change of only 0.82 and 0.51 risk factors per subject was noted for the diet/behavior change and control groups, respectively.  A one-way analysis of variance showed a significant different (P < .01) between the groups for the change in the total number of risk factors pre- to post-treatment.  Post hoc analysis showed that the changes in the exercise/diet/behavior change group were significantly greater than those of either the control or diet plus behavior change groups, whereas the change in total risk for the diet/behavior change group was not significantly different from that of the control group.  This change in total risk in combination with the change in the incidence of multiple risk factors for each group indicates that exercise in combination with diet and behavior modification reduces coronary heart disease risk to a greater extent than does diet plus behavior modification or control.

Author Conclusion:

A moderate program of diet, exercise, and behavior change reduces the coronary heart disease risk of obese adolescents. We do not know the long-term effects of the present treatment, but these short-term changes are encouraging. The exact mechanism whereby individual risk factors are changed is not clear. Nevertheless, we have demonstrated that the addition of a structured exercise program to modest dietary intervention reduces the multiple coronary heart disease risk profile of obese adolescents. This conclusion is in agreement with the recent American Heart Association position statement that exercise is an important factor leading to a more efficient cardiovascular system and reducing atherosclerotic risk.

Funding Source:
Government: NIH
University/Hospital: University of Michigan
Reviewer Comments:

No exclusion criteria provided. Demographics and health history of subject not described. Confounding variables were not described or considered in the analysis. Otherwise, the study was well designed.

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? No
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? No
  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? ???
  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? 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? No
  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? No
  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? 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? No
  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)? No
  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? No
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