DLM and Physical Activity

Citation:

Katzmarzyk PT, Leon AS, et al.  Targeting the Metabolic Syndrome with Exercise:  Evidence from the HERITAGE Family Study.  Medicine & Science in Sports & Exercise.  35:1703-1709, 2003.

 
Study Design:
Intervention study/efficacy trial in which the benefits of supervised aerobic training on multiple risk factors were examined.
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To determine the efficacy of aerobic exercise training for treating the metabolic syndrome in participants in the HERITAGE Family Study.
Inclusion Criteria:

HERITAGE Family Study inclusion criteria:

    *between the ages of 17 and 65 years

    *healthy, but sedentary (no regular physical activity over the previous 6 months)

    *systolic/diastolic BP less than 160/100 mmHg

For this article:

    *All of the above plus:

        -had measures available to identify the metabolic syndrome before & after  training program

Exclusion Criteria:

HERITAGE Family Study criteria:

    *Having confirmed or possible CAD, HTN (stage II or greater), chronic or recurrent respiratory problems, DM, use of lipid-lowering drugs, and BMI exceeding 40kg/m2

Description of Study Protocol:

Recruitment:  based on extensive publicity and advertisements at the 4 clinical centers (Arizona State University, Laval University, University of Minnesota, University of Texas at Austin). 

 

Design:  Intervention study/efficacy trial in which the benefits of supervised aerobic training on mulitple risk factors were examined.

 

Blinding used (if applicable):  Participants were not aware of their metabolic syndrome classification at any point in the study.

 

Intervention (if applicable): 

*Completed a 20 week standardized aerobic exercise training program

    -The aerobic fitness training response was assessed by 2 progressive maximal exercise tests conducted on separate days before as well as after training on Ergometrics 800S cycle ergometer connected to a metabolic cart

    -The training program involved three sessions per week of supervised exercise on a cycle ergometer.  Subjects started at 55% of their baseline VO2 max for 30 minutes per session and progressed in intensity or duration every 2 weeks after a standardized protocol until they were working at 75% VO2 max for 50 minutes per session for the final 6 weeks.

 

Statistical Analysis:

*Analyses are more descriptive than inferential, and more clinical than statistical 

*Significant differences in the prevalences of the metabolic syndrome and individual risk factors before and after training were tested using chi-squared analyses and an alpha of P<0.05

 

Data Collection Summary:

Timing of Measurements:

Measurements required for the definition of the metabolic syndrome (HDL, LDL, TG, BP, Waist circumference, glc) were obtained at baseline and after the 20 wk aerobic exercise program.

BP, HDL, and TG were measured after a 12-h fast on 2 separate days at baseline and 24 and 72 hours after the last exercise training session.  Values reported are the averages for the 2 pretraining and 2 posttraining measurements.

The aerobic fitness training response was assessed by 2 progressive maximal exercise tests conducted on separate days before as well as after training on Ergometrics 800S cycle ergometer connected to a metabolic cart.

Dependent Variables

  • Metabolic syndrome measurements: 

    *Change in HDL, LDL, BP, Fasting glc, TG from baseline

    *Change in weight from baseline

    *Change in VO2 max

Independent Variables (BASELINE):

*Age                *BMI                                *LDL        *BP

*Race               *Waist circimference       *HDL        *Fasting Glc

*Gender           *TG                                  *TG          *VO2 max

 

Control Variables:

*Aerobic exercise training prgram

 

Description of Actual Data Sample:

Initial N: 855

Attrition (final N):  621 {288 men (74 black, 214 white), 333 women (118 black, 215 white)

Age:  17-65 years of age

Ethnicity:  Black and white  

Other relevant demographics:

*The prevalence of the metabolic syndrome (>3 risk factors) was 16.9% for the entire sample.  The prevalence was similar among black men (18.9%), white men (19.2%), and black women (19.5%) but lower for white women (12.6%)

Anthropometrics:

*Among the sample of 105 participants who were classified as having the metabolic syndrome, there were no differences between white and black men, however, white women had significantly higher plasma TG and lower resting BP than black women. 

Location:  4 clinical centers in the United States (Arizona State University, Laval University, University of Minnesota, University of Texas at Austin). 

 

Summary of Results:

Table 3.  Prevalence (%) of risk factors pre- and posttraining amng 105 participants in the HERITAGE Family Study classified as having the metabolic syndrome at baseline

                        High TG        Low HDL        High BP        High Glc        High WC

Black Men            

    Pre                    93                100                71                43                43

    Post                  79                100                43                 29                43

White Men

    Pre                    76                 98                 46                 24                93

    Post                   63                 93                42                   7                 76

Black Women

    Pre                    26                  100              87                  35                100

    Post                  13                   96               65                   30                91

White Women

    Pre                    81                  100               26                  15                100

    Post                  62                     93              22                  19                  93

 

Other Findings:

*In general, the percentage of participants w/ each risk factor decreased consequent to the exercise training, w/ the exception of high BG in white women.

*Of the 105 participants w/ the metabolic syndrome at baseline, 32 people (30.5%) were no longer classified as having the syndrome after exercise training.  Of these 32 people, 43% reduced their TG, 16% increased their HDL, 38% reduced their BP, 9 % reduced their BG, and 28% reduced their WC below the threshold values used to diagnose the metabolic syndrome.

*The overall prevalence of the metabolic syndrome in the HERITAGE sample decreased from 16.9% before training to 11.8% after training.  On the other hand, only 4% (N=22) of the 516 participants who were not classified as having the metabolic syndrome before training were classified as having the syndrome after the training program. 

*The training effect (VO2 max) observed in the group of participants with the metabolic syndrome (16.3%) was quite similar to that of the entire sample (17.6%).

 

Author Conclusion:

In summary, the results of this study indicate that physical activity is useful for treating the metabolic syndrome.  The results were similar in men and women, and in black and white participants, suggesting that the effects of exercise training may be generalizable to a large segment of the North American population.  The use of exercise as a component of therapeutic lifestyle change programs in people with multiple risk factors is encouraged.

Taken together, the results of these studies and those from the present study reinforce the notion that physical activity is an important correlate of and treatment option for the metabolic syndrome.

The effects of exercise training observed in this study represent an important aspect of the primary prevention of chronic disease because the participants with the metabolic syndrome were at high risk of future disease due to the presence of mulitple risk factors.

Funding Source:
Government: NHLBI
University/Hospital: Henry L. Taylor Professorship In Exercise Science and Health Enhancement, George A. Bray Chair in Nutrition.
Reviewer Comments:

The author stated strengths (large biracial sample, rigorously standardized supervised exercise program that limited problems with adherence) and limitations (reliance on participating to act as their own controls, lack of randomized control design).

The author includes ideas for future studies (ex:  clinical trials using intent-to-treat analyses that dtermine the effectiveness or efficiency of physical activity in treating the metabolic syndrome).

It was benefical that the subjects looked at both black's and white's and males and females.

One thing that needed to be controlled was diet and could effect these results greatly.  Patients should have had food histories taken or food diaries presented every so often to determine if diets were changing also.

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? 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
  3.1. 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
  3.2. 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
  3.3. 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
  3.4. 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
  3.5. 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? Yes
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? 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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? 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
  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? Yes
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  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.) Yes
  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.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  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
  5.4. 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? N/A
  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
  6.3. 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
  6.4. 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? N/A
  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
  6.7. 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? 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
  7.4. 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)? 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
  8.6. 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