Pediatric Weight Management

PWM: Physical Activity and Inactivity (2006)

Citation:

Owens S, Gutin B, Allison J, Riggs S, Ferguson M, Litaker M, Thompson W. Effect of physical training on total and visceral fat in obese children. Medicine & Science in Sports & Exercise 1999;31:143-148

PubMed ID: 9927022
 
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:

This study was undertaken to test the hypothesis that controlled physical training, without dietary intervention, would have a favorable impact on visceral adipose tissue (VAT) and percent body fat (%BF) in obese children.

Inclusion Criteria:

Child needed to have a triceps skinfold greater than the 85th percentile for gender, age, and ethnicity

Exclusion Criteria:

Subjects may not be involved in any other weight control or exercise physical activity.

Description of Study Protocol:

The children underwent baseline testing and were randomly assigned, within gender and ethnicity as designated by the parents, to the physical training or control groups. Before and after 4 months of intervention, measurements were obtained for VAT, TFM, %BF, daily physical activity, and cardiovascular fitness. The intervention involved 4 months of controlled physical training 5 d x wk(-1), 40 min per session, at a mean heart rate (HR) of 157 beats x min(-1). The estimated energy expenditure (EE) per training session was 925+/-201 kJ.

Physical Training Program

The physical training program was designed to provide a substantial EE during each training session.  The goal for each child was to keep his/her HR above 150 beats/min-1, which equates to an intensity of approximately 70-75% of maximal HR for this age group.  A previous training study in our laboratory indicated that this intensity resulted in a relatively high EE and favorable changes in body composition, and that it would be feasible for obese children to maintain for a 40-min training session.  A typical training session included 20 min of exercising on machines (e.g., treadmill, stationary cycle, trampoline) and 20 min playing games (e.g., basketball, dodge ball, tag).  Each child wore a HR monitor (Polar Vantage, Port Washington, NY) during every session.  After each session, the min-by-min HR data were downloaded into a computer and displayed to the child.  As incentives, children were paid $1 for each exercise session attended and earned points for maintenance of the target HR.  Prizes were given after accumulation of specified numbers of points.

Data Collection Summary:

Total body mass, total body fat mass, total body fat-free mass, and %BF were measured with DEXA.

VAT and SAAT were determined using a 1.5 Tesla MRI system. Because of budgetary considerations, a subsample of 60 consecutive subjects participated in this aspect of the data collection.  Spin echo techniques were used to produce T1 weighted images demonstrating good contrast between adipose and nonadipose tissues.  Details of the MRI acquisition were as follows:  repetition time: 450 ma; echo time: 12 ms; field of view: 400 MM; matrix: 192X256; number of excitations: 1.

Respiratory compensation was used to reduce artifacts caused by respiratory motion.  With subjects in the supine position, a series of five 1-cm wide transverse images was acquires from the lumbar spine of the region of the abdomen, beginning at the interior border of the fifth lumar vertebra and proceeding toward the head.  A 2-mm gap between images was utilized tpo prevent cross talk.  Tissues superior to and inferior to the five slices were saturated to prevent blood flow in the aorta or inferior vena cava from appearing as high intens artifacts in the images.  VAT was quantifies as adipose tissue within a region of interest (ROI) defined by a line drawn through the middle of the abdominal and back muscles.  VAT and SAAT were segmented using a semiautomated technique on an ISG Allegro image analysis workstation.  An experienced observer selected an image intensity threshold that set nonfat tissues to zero intensity.

Cardiovascular fitness was expressed as HR during submaximum cycling at a work rate of 49 W on an ergometer.  SubmaxHR has been found to be a satisfactory index for change in fitness produce by physical training in children.  For testing, the ergometer work rate was increased gradually until it reached the 49 W level, after which the child maintained that power output for 8 m.  Submax was the average HR over the last 5 minutes, as measured with an ECG embedded in the echocardiograph.

Total daily and moderate-to-very hard physical activity estimated was estimated from 7-day recalls.  Using a semistructured interview format, the interviewer asked the child to record time spent sleeping and doing physical activities during the 7 d just before the interview.  Thus, the recall included the physical training associated with the exercise classes for the group involved in the physical training during this period.  The interviewer guided the subjects through the recall process, day by day, to determine the intensity and duration of the activities. 

The child was asked to recall the intensities of the activities as either being moderate, very hard, or hard.  Only those activities that were engaged in for at least 10 minutes were included.  Total hrs spent sleeping and in moderate, hard, and very hard were calculated from daily reports.  Weekly hrs spent in light activity were derived by subtraction.  Total energy used was estimated from metabolic equivalents assigned to the five activity categories as follows: sleep, light, moderate, hard, and very hard.  Values from the moderate, hard, and very hard categories were summed to derive MVHPA

Description of Actual Data Sample:

Eighty-one children

Summary of Results:

Of the 18 children who underwent baseline testing, two were dropped from the study before group assignment for medical reasons uncovered at baseline (one orthopedic and one cardiac). Of the 40 children originally assigned to the physical training group, three dropped out before post-testing.  Two children who completed post-testing did not meet the criterion of at least 3 d/wk attendance and were excluded from the primary statistical analyses.  Thus, 35 subjects were included in the physical training group for the primary analyses.  (When the analyses were repeated with the two low-attendance subjects included, the group comparisons yielded the same conclusions).  All 39 children assigned to the control group completed post-testing.

For the primary analyses of the physical training group, the average rate of attendance for the 5 d/wk, 4 month long program was 87 +/- 10%, the equivalent of 4.4 d/wk.  The mean HR during the sessions was 157 +/- 7 beats/min and the mean EE per session was 925 +/- 201 kJ.  This equates to an average training intensity of approximately 5.3 MET, which falls toward the lower end of the “hard” intensity category (5.0-6.9 MET) on the 7-d physical activity recall.  These results indicate that a substantial dose of physical training was imparted to the subjects. 

There were no significant differences between the groups for any of the baseline variables. 

Relative to the control group, the physical training group declined significantly in %BP, resulting from a significant decline in TFM and a significantly greater increase in FFM.  The two groups show different responses on the following measures:

  • Both VAT and SAAT measures: the control group increased significantly in these two fat deposits compared with the physical training group
  • Exercise heart rate: the physical training group showed significantly reduced exercise heart rate suggesting that their cardiovascular fitness was influenced favorably 
  • MVHPA score: the difference between change score MVHPA, as measured by the 7-day recall, was significant with the physical training group increasing and the control decreasing. 
Author Conclusion:

This study showed that during physical training obese children:

  1. were capable of participating in a substantial amount of high intensity physical training over a 4-month period
  2. accumulated significantly less VAT as compared with nonexercising controls
  3. experienced other beneficial changes in total and regional body composition.

 

This suggest that increasing the physical activity of obese children, even without dietary intervention, can improve aspects of body composition that are linked with unfavorable risk factors for cardiovascular disease and non-insulin-dependent diabetes mellitus.

Funding Source:
Government: NHLBI,
University/Hospital: Medical College of Georgia
Not-for-profit
0
Foundation associated with industry:
Reviewer Comments:
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? Yes
  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? 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%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? No
  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? 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
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? 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