Pediatric Weight Management

PWM: Prescribed Diet Plan and Nutrition Education (2006)

Citation:

Rocchini AP, Katch V, Anderson J, Hinderliter J, Becque D, Martin M, Marks C. Blood Pressure in Obese Adolescents: Effect of Weight Loss. Pediatrics 1988;82:16-23.

PubMed ID: 3288957
 
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 determine the BP distribution of a group of obese adolescents both before and after weight loss and to determine whether weight loss produced by a program of caloric restriction, behavior change, and exercise causes a greater reduction in BP than that which is associated with a weight loss program composed of caloric restriction and behavior change alone.

Inclusion Criteria:

Obesity was defined as weight for height greater than the 75th percentile for age and sex and triceps and subscapular skin folds greater than the 80th percentile for age and sex

Exclusion Criteria:

None cited.

Description of Study Protocol:

Diet Group

To study the effect of weight loss on BP, the subjects were randomly assigned to one of three treatment groups. A group of 26 obese adolescents were assigned to and 22 completed a 20-week weight loss program consisting of diet and behavior change (diet group).  The diet was a modification of the caloric exchange program and was designed to produce a weight loss of approximately 2.2 kg (1 lb/wk). The behavior change component of the program was composed of a one-hour class each week for 20 weeks that consisted of record keeping, stimulus control, changing eating behavior, and reinforcement of altered behavior.

Exercise Group

A total of 25 obese adolescents were assigned to and 23 completed a 20-week weight loss program composed of diet, behavior change and exercise (exercise group). The diet and behavior change was as previously described. The exercise program consisted of three 1-hour exercise classes per week for 20 weeks.  Each class included warm-up exercise and aerobic activity.  The warm-up exercises consisted of progressive stretching techniques and muscle strengthening for ten minutes at the beginning of each exercise class.  Aerobic activities were used for total body activities designed to maintain heart rate for at least 40 minutes at greater than 70% to 75% of maximal exercise heart rate.  The duration of exercise was initially 15 minutes and was progressively increased to 40 minutes.  Specific activities included walking, jogging, swimming, aerobic dance, soccer, and other recreational activities.  To ensure adequate supervision and motivation, there were two to four adolescents per exercise leader.

Control

A total of 22 obese adolescents were assigned to the control group and 18 completed the 20-week study and received no weight loss program for 20 weeks.  There were no significant differences between the three treatment groups with respect to age or gender. The 72 obese adolescents were tested before and 63 were tested after the three 20-week programs. The ten non-obese adolescents were only tested once.

Data Collection Summary:

Weight was measured in kilograms using a balance beam scale and height was measured to the nearest 0.1 cm using a stabilometer.

 

All subjects were admitted overnight to the clinical research center at the University of Michigan Hospitals.  All adolescents fasted after 10 pm the evening preceding the study and were maintained in a supine position after 4am the morning of the study.  A heparin lock was inserted at 7:30am while the adolescents were supine.  The heart rate and arterial pressure during the 30-minute rest period were the values recorded.  Mean arterial pressure also was calculated as diastolic pressure plus one-third pulse pressures.  All adolescents also performed a multistaged discontinuous exercise test in the sitting position using an electronically braked bicycle ergometer. 

The first two stages were done at 15 and 30 W.  Subsequent work stages were increased by 30-W increments until the adolescent could no longer turn the pedals at 60 rpm. Each work rate was performed for five minutes and there was a three minute rest period between every other work stage. 

The following measurements were taken during each stage of exercise: BP, heart rate, tidal volume, oxygen uptake, and carbon dioxide production.  Gas exchange was continuously monitored by an online measurement of ventilation rate, % of carbon dioxide, and % of oxygen. 

Following the exercise test, all adolescents were given lunch and then had body composition measured by hydrostatic weighing.  Finally, forearm blood flow was measured in the right arm using a mercury in Silastic strain gauge plethsmography and venous occlusion.  During measurements of forearm blood flow, circulation to the hand was arrested by inflating a cuff around the wrist to the point of suprasystolic pressure.  Initially,  four blood flows were recorded every 10 seconds and an average value was calculated while BP was measured in the left arm with a Critikon monitor.  Forearm vascular resistance was calculated by dividing mean arterial pressure by forearm blood flow.  Minimum forearm vascular resistance was assessed by inflating the cuff on the upper arm to above systolic pressure for ten minutes to occlude arterial flow while having the adolescent squeeze a ball ten times.  After the release of the arterial occlusion, forearm blood flow was measured after 5 seconds and every 10 seconds thereafter for three minutes.  BPs were measured at approximately 30-second intervals after release of the arterial occluding cuff.  The peak blood flow recorded after release of arterial occlusion was used to calculate the minimal forearm vascular resistance.

Description of Actual Data Sample:

72 obese adolescents (34 boys and 38 girls) with a mean age of 12.6 years (range 10 to 17 years) and ten nonobese adolescents with a mean age of 12.2 years (range 10 to 14 years)

Summary of Results:

Obese versus Non-Obese

We observed that when compared with the ten nonobese adolescents, the 72 obese adolescents had significantly higher systolic, diastolic, and mean arterial pressures. Because BP is affected in childhood by both age and sex, to compare our group of obese adolescents with the adolescent population in general, a z score BP distribution was calculated for obese adolescents using data from the second National Health and Nutrition Examination Survey.  We observed that these obese adolescents had both a systolic and diastolic BP distribution that was significantly skewed to the right.  Both the systolic and diastolic BP distributions for the obese adolescents were skewed greater than 1 SD to the right of the children in the second National Health and Nutrition Examination Survey. 

There was also a significant correlation between the z-score BP values and total body weight and fat weight.  No significant relationship was observed between lean body weight and the z score BP, however.  In addition to having an elevated BP, the obese children also had tachycardia when compared with our nonobese group.  There was also a significant positive correlation between resting heart rate and z score systolic and diastolic BP values.

The effect of weight loss on BP and heart rate was evaluated by comparing the changes that occurred after 20 weeks of weight loss induced by either diet and behavior change alone or in combination with exercise that which occurred after a 20-week control period. 

Adiposity Changes in Obese Treatment Groups

Of the 72 obese adolescents who started in the program and were initially tested, there were 63 adolescents who completed both weight loss or control periods and had a posttest performed.  No significant differences were noted between the three groups of obese adolescents prior to the weight loss program. 

When compared with the obese control group, the two 20-week weight loss groups experienced a modest but significant decrease in body weight (P < .01). The modest decrease in body weight observed in the two weight loss groups was associated with a significant change in body composition (P < .01).  Although the exercise group tended to have a greater decrease in percentage of fat (measured by hydrostatic weighing), there were no significant differences noted between the two weight loss groups with respect to any of the anthropometric variables measured.

Changes in Cardiovascular Fitness

Prior to weight loss, the heart rate and oxygen consumption response to bicycle exercise were similar in all three groups of obese adolescents.  After the 20-week program, both weight loss groups of children experienced a significant decrease in resting heart rate; however, this decrease in heart rate was significantly greater in the weight loss group that exercised (P < .01).  In addition, only the group of children in the exercise group experienced a decrease in both heart rate and oxygen consumption at the 60-W submaximal exercise stage (P < .01)  The exercise group also tended to have the largest increase in maximal oxygen consumption and endurance.

When compared with the obese control group, the two weight loss groups experienced significant decreases in systolic and diastolic mean and z score BP values.  After the 20-week weight loss program, both weight loss groups experienced a decrease in BP; however, when we performed an analysis of covariance (with the change in body weight as the concomitant variable), we observed that there was a significantly greater decrease in resting systolic BP in the exercise group than was observed in the diet group.  In addition, differences between the two weight loss groups in their response to bicycle exercise were also noted.  As can be seen in Table 3, the increase in diastolic and mean BP that occurs during both submaximal and maximal exercise were significantly less in the exercise group following the 20-week weight loss program (P< .01).

Author Conclusion:

We have demonstrated that obese adolescents have an elevated BP that is reduced with weight loss. We have also shown that a weight loss program that incorporates exercise with calorie restriction produces the most desirable effects in BP reduction.  Finally, we have demonstrated that obese adolescents appear to have these structural changes present in the forearm resistance vessels and that these structural changes are reversible

Funding Source:
Reviewer Comments:

No exclusion criteria specified. No limitations discussed. Reasons for withdrawals were not described Otherwise, a well designed study with important outcomes.

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? 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? ???
  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? 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? ???
  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? 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? 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? 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