Journal of Endocrinology and Metabolism, ISSN 1923-2861 print, 1923-287X online, Open Access
Article copyright, the authors; Journal compilation copyright, J Endocrinol Metab and Elmer Press Inc
Journal website http://www.jofem.org

Original Article

Volume 6, Number 2, April 2016, pages 35-45

Exercise Dose Effects on Insulin Resistance Indicators in Postmenopausal Women: A Randomized Trial

Figure

Figure 1.
Figure 1. Change in biomarker concentrations across five levels of “time in zone” averaged over 52 weeks, BETA Trial, Alberta, Canada, 2010 - 2013, treatment arms combined. Sample sizes were: n = 77, n = 78, n = 76, n = 77, n = 78 for quintiles 1 to 5, respectively. HOMA-IR: homeostasis model assessment of insulin resistance = fasting glucose (mM) × fasting insulin (μIU/mL)/22.5; “time in zone”: time spent exercising at an intensity of 65-75% maximum heart rate reserve. Statistical testing: *P < 0.05 comparing the least-squares mean biomarker change at that “time in zone” to < 57 min/week, adjusted for baseline biomarker level. P for trend reflects the statistical significance of a linear trend with quintiles of “time in zone” treated as a continuous variable, adjusted for baseline biomarker level.

Tables

Table 1. Baseline Characteristicsa of Randomized Participants in the BETA Trial, Alberta, Canada, 2010 - 2013
 
Baseline characteristicModerateHigh
HOMA-IR: homeostasis model assessment of insulin resistance = fasting glucose (mM) × fasting insulin (μIU/mL)/22.5 [27]. SI conversions: to convert fasting insulin to pmol/L, multiply by 6.945; glucose to mmol/L, multiply by 0.0555; leptin to μg/L, multiply by 1.00; adiponectin and resistin SI units not available. aBaseline values were missing for biomarker concentration (n = 14). bThere were no statistically significant differences at baseline between high and moderate groups for these variables except for glucose and adiponectin, P value = 0.02 and 0.05, respectively.
n (%)n (%)
Number of participants randomized200200
Race/ethnicity
  White186 (93%)172 (86%)
  Other14 (7%)28 (14%)
Mean ± SDMean ± SD
Age (years)59.5 ± 5.159.4 ± 4.8
Maximal oxygen consumption (mL/kg/min)26.8 ± 5.026.7 ± 5.3
Body mass index (kg/m2)29.4 ± 4.429.1 ± 4.4
Percent body fat (%)40.7 ± 5.940.5 ± 5.8
Intra-abdominal fat (cm2)133.4 ± 49.3125.6 ± 50.8
Lean mass (kg)43.9 ± 5.744.1 ± 5.5
Median (quartile 1, 3)Median (quartile 1, 3)
Total energy intake (kcal/day)1,412 (1,115, 1,785)1,379 (999, 1,797)
Alcohol intake (g/day)2.4 (0.7, 7.5)3.0 (0.9, 6.5)
Fat intake (g/day)50.5 (37.2, 67.5)49.3 (35.5, 70.6)
Fiber intake (g/day)17.3 (12.9, 22.4)16.8 (12.3, 22.5)
Carbohydrate intake (g/day)175.3 (139.8, 227.6)169.3 (126.9, 217.7)
Glycemic load (g/day)79.9 (62.2, 102.2)76.1 (56.2, 102.2)
Past year total physical activity (MET-hours/week)
  Total activity90.6 (60.6, 121.9)89.0 (62.2, 115.8)
  Occupational activity25.9 (4.5, 55.2)34.2 (2.6, 56.3)
  Household activity41.0 (27.0, 60.6)40.4 (28.3, 60.1)
  Recreational activity7.6 (2.3, 13.0)6.9 (2.4, 13.3)
Biomarker concentration
  Insulin (µIU/mL)8.7 (5.9, 12.5)8.3 (5.0, 12.1)
  Glucose (mg/dL)b91 (86, 98)89 (85, 95)
  HOMA-IR2.1 (1.3, 2.9)1.8 (1.1, 2.7)
  Leptin (ng/mL)39.2 (23.1, 61.1)38.4 (20.0, 58.6)
  Adiponectin (µg/mL)b21.1 (13.4, 40.5)26.5 (14.2, 50.1)
  Resistin (ng/mL)24.9 (20.6, 29.9)25.6 (20.2, 32.2)

 

Table 2. High/Moderate Ratio of Geometric Mean Biomarker Levels Over 12 Months, Intention-to-Treat Analysis in the BETA Trial, Alberta, Canada, 2010 - 2013
 
BiomarkerGroupaBaseline geometric mean95% CI6-month geometric mean95% CI12-month geometric mean95% CI12-month percent changeTreatment effect ratio95% CIBetween-group P-valueb
HOMA-IR: homeostasis model assessment of insulin resistance = fasting glucose (mM) × fasting insulin (μIU/mL)/22.5. SI conversions: to convert fasting insulin to pmol/L, multiply by 6.945; glucose to mmol/L, multiply by 0.0555; leptin to μg/L, multiply by 1.00; adiponectin and resistin SI units not available. aAvailable sample sizes for moderate/high groups were as follows: insulin, 188/195; glucose, 190/195; HOMA-IR, 187/195; leptin, 191/192; adiponectin, 190/195; resistin, 191/194. Sample sizes varied between biomarkers due to insufficient blood volume (n = 1) and exclusion of extreme concentrations at baseline (n = 1 - 3 participants depending on biomarker). bStatistical test for a significant high versus moderate group difference in biomarker levels over 12 months from the linear mixed model, adjusted for biomarker level at baseline.
Insulin, µIU/mLModerate8.78.0 - 9.38.17.5 - 8.88.07.3 - 8.6-8.00.960.90 - 1.030.26
High7.77.1 - 8.47.36.7 - 7.96.96.4 - 7.5-10.4
Glucose, mg/dLModerate9291 - 939190 - 929089 - 92-1.71.000.99 - 1.010.59
High9089 - 918988 - 908987 - 90-1.0
HOMA-IRModerate2.01.8 - 2.11.81.7 - 2.01.81.6 - 1.9-10.40.970.90 - 1.040.36
High1.71.6 - 1.91.61.5 - 1.81.51.4 - 1.7-11.3
Leptin, ng/mLModerate36.132.4 - 40.329.626.5 - 33.228.425.4 - 31.8-21.40.930.84 - 1.020.13
High34.530.9 - 38.625.722.7 - 29.026.423.4 - 29.8-23.5
Adiponectin, µg/mLModerate23.120.7 - 25.920.718.5 - 23.123.421.0 - 26.11.10.980.92 - 1.040.45
High26.723.8 - 30.023.120.5 - 26.026.323.3 - 29.6-1.6
Resistin, ng/mLModerate24.823.7 - 25.925.524.3 - 26.825.224.1 - 26.41.60.980.94 - 1.020.23
High25.324.0 - 26.725.824.5 - 27.124.423.2 - 25.7-3.4

 

Table 3. Intention-to-Treat Analysis Stratified by Categories of Baseline Body Mass Index, BETA Trial, Alberta, Canada, 2010 - 2013
 
BiomarkerTreatment effecta
GroupN6-month percent change from baseline12-month percent change from baselineRatio of high/moderate95% CIBetween-group PbP-interactionc
HOMA-IR: homeostasis model assessment of insulin resistance = fasting glucose (mM) × fasting insulin (μIU/mL)/22.5. aHigh/moderate ratio of geometric means for biomarker levels over 12 months adjusted for biomarker level at baseline. bStatistical test for a significant high versus moderate group difference in biomarker level over 12 months from the linear mixed model, adjusted for biomarker level at baseline. cStatistical test for a significant cross-product term: (group assignment × baseline BMI as continuous variable) in a linear mixed model, adjusted for biomarker level at baseline.
Insulin
  BMI < 30 kg/m2Moderate114-5.9-8.80.960.89 - 1.040.350.98
High121-4.1-9.3
  BMI ≥ 30 kg/m2Moderate74-6.8-6.70.960.86 - 1.060.40
High74-9.4-12.1
Glucose
  BMI < 30 kg/m2Moderate115-1.3-2.01.000.98 - 1.020.970.41
High1210.1-0.7
  BMI ≥ 30 kg/m2Moderate750.3-1.10.990.97 - 1.010.33
High74-1.3-1.5
HOMA-IR
  BMI < 30 kg/m2Moderate113-7.6-10.90.970.89 - 1.060.520.89
High121-3.9-9.9
  BMI ≥ 30 kg/m2Moderate74-6.6-9.40.950.85 - 1.070.41
High74-10.6-13.5
Leptin
  BMI < 30 kg/m2Moderate116-20.8-24.20.980.87 - 1.090.660.50
High121-25.1-22.6
  BMI ≥ 30 kg/m2Moderate75-13.3-16.40.870.73 - 1.030.09
High71-27.0-25.0
Adiponectin
  BMI < 30 kg/m2Moderate116-11.51.60.980.91 - 1.050.530.67
High121-14.2-2.0
  BMI ≥ 30 kg/m2Moderate75-9.20.40.980.90 - 1.070.67
High73-12.1-1.0
Resistin
  BMI < 30 kg/m2Moderate1163.73.60.950.90 - 1.000.040.12
High121-0.8-5.5
  BMI ≥ 30 kg/m2Moderate751.1-1.41.030.96 - 1.090.43
High736.40.3

 

Table 4. Intention-to-Treat Analysis Stratified by Categories of Baseline Age, BETA Trial, Alberta, Canada, 2010 - 2013
 
BiomarkerTreatment effecta
GroupN6-month percent change from baseline12-month percent change from baselineRatio of high/moderate95% CIBetween-group PbP-interactionc
HOMA-IR: homeostasis model assessment of insulin resistance = fasting glucose (mM) × fasting insulin (μIU/mL)/22.5. aHigh/moderate ratio of geometric mean biomarker level over 12 months, adjusted for biomarker level at baseline. bStatistical test for a significant high versus moderate group difference in biomarker level over 12 months from the linear mixed model, adjusted for biomarker level at baseline. cStatistical test for a significant cross-product term: (group assignment × baseline age as continuous variable) in a linear mixed model, adjusted for biomarker level at baseline.
Insulin
  Age < 60 yearsModerate106-3.9-6.50.950.87 - 1.040.250.61
High121-5.2-10.5
  Age ≥ 60 yearsModerate82-9.3-9.90.980.89 - 1.080.68
High74-7.2-10.1
Glucose
  Age < 60 yearsModerate108-0.3-1.30.990.97 - 1.000.140.79
High121-0.4-1.5
  Age ≥ 60 yearsModerate82-1.3-2.31.010.99 - 1.030.36
High74-0.3-0.0
HOMA-IR
  Age < 60 yearsModerate106-4.0-7.20.940.86 - 1.040.210.77
High121-5.6-11.9
  Age ≥ 60 yearsModerate81-11.2-14.41.000.90 - 1.120.95
High74-7.5-10.1
Leptin
  Age < 60 yearsModerate108-13.6-8.70.840.74 - 0.960.010.03
High120-25.1-27.8
  Age ≥ 60 yearsModerate83-23.3-35.51.070.92 - 1.250.38
High72-26.5-15.6
Adiponectin
  Age < 60 yearsModerate108-12.13.70.980.91 - 1.060.580.68
High121-13.0-2.3
  Age ≥ 60 yearsModerate83-8.7-2.10.980.89 - 1.070.62
High73-14.4-0.5
Resistin
  Age < 60 yearsModerate1081.72.50.990.94 - 1.050.820.85
High1212.4-2.9
  Age ≥ 60 yearsModerate834.00.50.950.89 - 1.020.14
High731.1-4.2

 

Table 5. High/Moderate Ratio of Geometric Mean Biomarker Levels Over 12 Months, Per-Protocol Analysisa in the BETA Trial, Alberta, Canada, 2010 - 2013
 
BiomarkerGroupbBaseline geometric mean95% CI6-month geometric mean95% CI12-month geometric mean95% CI12-month percent changeTreatment effect ratio95% CIBetween-group
P-valuec
HOMA-IR: homeostasis model assessment of insulin resistance = fasting glucose (mM) × fasting insulin (μIU/mL)/22.5. SI conversions: to convert fasting insulin to pmol/L, multiply by 6.945; glucose to mmol/L, multiply by 0.0555; leptin to μg/L, multiply by 1.00; adiponectin and resistin SI units not available. aAverage exercise time over weeks 13 - 52 was 135 - 150 min/week (moderate) or ≥ 270 min/week (high). bAvailable sample sizes for moderate/high groups were as follows: insulin, 57/80; glucose, 58/80; HOMA-IR, 57/80; leptin, 58/79; adiponectin, 58/80; resistin, 58/80. Sample sizes varied between biomarkers due to exclusion of extreme concentrations at baseline (n = 2 for insulin, HOMA-IR and leptin). cStatistical test for a significant high versus moderate group difference in biomarker levels over 12 months from the linear mixed model, adjusted for biomarker level at baseline.
Insulin, µIU/mLModerate8.87.6 - 10.18.37.3 - 9.57.86.7 - 9.2-10.60.890.80 - 0.990.03
High7.56.6 - 8.66.65.8 - 7.56.15.4 - 7.0-19.1
Glucose, mg/dLModerate9289 - 949290 - 949088 - 92-1.730.980.96 - 1.000.03
High8886 - 898786 - 898685 - 88-1.67
HOMA-IRModerate2.01.7 - 2.31.91.6 - 2.21.71.5 - 2.1-11.90.870.78 - 0.980.02
High1.61.4 - 1.91.41.2 - 1.61.31.1 - 1.5-20.4
Leptin, ng/mLModerate33.927.5 - 41.829.624.5 - 35.726.321.4 - 32.4-22.40.770.65 - 0.900.002
High30.926.0 - 36.719.616.1 - 23.820.316.8 - 24.5-34.4
Adiponectin, µg/mLModerate22.018.4 - 26.220.817.4 - 24.823.819.9 - 18.58.20.920.84 - 1.020.11
High26.422.1 - 31.621.718.0 - 26.227.222.6 - 32.93.2
Resistin, ng/mLModerate25.123.2 - 27.224.422.3 - 26.824.722.7 - 26.8-1.80.990.92 - 1.060.78
High25.723.5 - 28.025.823.6 - 28.223.721.6 - 26.1-7.5