Cross-Cultural Activity Participation Study
Objective: The purpose of this study was to determine the association between moderate-intensity physical activity (PA) and fasting insulin levels among African-American (n = 47), Native American (n = 46), and Caucasian women (n = 49), aged 40-83 years, enrolled in the Cross-Cultural Activity Participation Study. Associations by race/ethnicity, levels of central obesity, and cardiorespiratory fitness were also examined.
Research Design And Methods: Physical activity scores were obtained from detailed PA records that included all PA performed during two consecutive 4-day periods scheduled 1 month apart. Using MET intensity (the associated metabolic rate for a specific activity divided by a standard resting metabolic rate), PA was expressed as MET-min (the product of the minutes for each activity times the MET intensity level) per day of energy expended in moderate (3-6 METs) and moderate/vigorous (>3 METs) PA. Fasting insulin levels were determined by radioimmunoassay. Data were analyzed by multiple linear regression analysis.
Results: After adjusting for race/ethnicity, age, educational attainment, and site, an increase of 30 min of moderate-intensity PA was associated with a 6.6% lower fasting insulin level (P < 0.05). The association was similar among races/ethnicities, centrally lean and centrally obese women, and women with low and high cardiorespiratory fitness levels.
Conclusions: These findings lend support to the 1995 Centers for Disease Control and Prevention and American College of Sports Medicine recommendations for an accumulation of 30 min/day in moderate-intensity PA. They also contribute to the growing literature suggesting that moderate amounts of PA have a significant role in reducing the burden of hyperinsulinemia and diabetes among ethnic populations at highest risk for these conditions.
Physical activity (PA) has a beneficial effect in reducing plasma insulin levels among people with and without type 2 diabetes . Much of the evidence for this effect is from estimates of total daily PA and participation in vigorous PA. Few studies have reported an effect of moderate-intensity PA on insulin levels. In the Insulin Resistance Atherosclerosis Study, Mayer-Davis et al. showed a significant association between moderate- and vigorous-intensity PA and insulin sensitivity among people with and without type 2 diabetes (P < 0.05). In the San Luis Valley Study, Regensteiner et al. showed an inverse association between PA and fasting insulin levels (P < 0.05).
The mechanisms by which PA decreases insulin resistance and hyperinsulinemia are not yet fully understood. PA directly reduces insulin resistance and hyperinsulinemia by increasing the number and activity of glucose transporters (especially the GLUT4 isoform), in both muscle and adipose tissue . In addition, PA may indirectly reduce insulin resistance and hyperinsulinemia by promoting fat loss and preservation of lean body mass .
Whereas most studies generally show that vigorous PA may reduce insulin concentrations, these results are not directly applicable to most women who do not regularly perform such vigorous PA. In 1995, the Centers for Disease Control and Prevention (CDC) and the American College of Sports Medicine (ACSM) released a statement recommending that all U.S. adults accumulate at least 30 min of moderate-intensity PA on most, if not all, days of the week . This moderate-intensity recommendation differs from previous recommendations suggesting that adults should exercise vigorously for at least 20 min three times per week . Few studies have examined the association between moderate-intensity PA, at levels recommended by the CDC and ACSM, and fasting insulin levels. It is important to examine the association between PA and fasting insulin by levels of central obesity and cardiorespiratory fitness. Centrally obese individuals are at increased risk for insulin resistance and may be more likely to decrease their risk through increased PA , and moderate-intensity PA is relatively more strenuous for an individual with a low cardiorespiratory fitness level than an individual with a high cardiorespiratory fitness level. The purpose of this study was to determine the association between moderate-intensity PA and fasting insulin levels and to examine possible differences in this association by race/ethnicity, central obesity, and cardiorespiratory fitness level.
Objective: The purpose of this study was to determine the association between moderate-intensity physical activity (PA) and fasting insulin levels among African-American (n = 47), Native American (n = 46), and Caucasian women (n = 49), aged 40-83 years, enrolled in the Cross-Cultural Activity Participation Study. Associations by race/ethnicity, levels of central obesity, and cardiorespiratory fitness were also examined.
Research Design And Methods: Physical activity scores were obtained from detailed PA records that included all PA performed during two consecutive 4-day periods scheduled 1 month apart. Using MET intensity (the associated metabolic rate for a specific activity divided by a standard resting metabolic rate), PA was expressed as MET-min (the product of the minutes for each activity times the MET intensity level) per day of energy expended in moderate (3-6 METs) and moderate/vigorous (>3 METs) PA. Fasting insulin levels were determined by radioimmunoassay. Data were analyzed by multiple linear regression analysis.
Results: After adjusting for race/ethnicity, age, educational attainment, and site, an increase of 30 min of moderate-intensity PA was associated with a 6.6% lower fasting insulin level (P < 0.05). The association was similar among races/ethnicities, centrally lean and centrally obese women, and women with low and high cardiorespiratory fitness levels.
Conclusions: These findings lend support to the 1995 Centers for Disease Control and Prevention and American College of Sports Medicine recommendations for an accumulation of 30 min/day in moderate-intensity PA. They also contribute to the growing literature suggesting that moderate amounts of PA have a significant role in reducing the burden of hyperinsulinemia and diabetes among ethnic populations at highest risk for these conditions.
Physical activity (PA) has a beneficial effect in reducing plasma insulin levels among people with and without type 2 diabetes . Much of the evidence for this effect is from estimates of total daily PA and participation in vigorous PA. Few studies have reported an effect of moderate-intensity PA on insulin levels. In the Insulin Resistance Atherosclerosis Study, Mayer-Davis et al. showed a significant association between moderate- and vigorous-intensity PA and insulin sensitivity among people with and without type 2 diabetes (P < 0.05). In the San Luis Valley Study, Regensteiner et al. showed an inverse association between PA and fasting insulin levels (P < 0.05).
The mechanisms by which PA decreases insulin resistance and hyperinsulinemia are not yet fully understood. PA directly reduces insulin resistance and hyperinsulinemia by increasing the number and activity of glucose transporters (especially the GLUT4 isoform), in both muscle and adipose tissue . In addition, PA may indirectly reduce insulin resistance and hyperinsulinemia by promoting fat loss and preservation of lean body mass .
Whereas most studies generally show that vigorous PA may reduce insulin concentrations, these results are not directly applicable to most women who do not regularly perform such vigorous PA. In 1995, the Centers for Disease Control and Prevention (CDC) and the American College of Sports Medicine (ACSM) released a statement recommending that all U.S. adults accumulate at least 30 min of moderate-intensity PA on most, if not all, days of the week . This moderate-intensity recommendation differs from previous recommendations suggesting that adults should exercise vigorously for at least 20 min three times per week . Few studies have examined the association between moderate-intensity PA, at levels recommended by the CDC and ACSM, and fasting insulin levels. It is important to examine the association between PA and fasting insulin by levels of central obesity and cardiorespiratory fitness. Centrally obese individuals are at increased risk for insulin resistance and may be more likely to decrease their risk through increased PA , and moderate-intensity PA is relatively more strenuous for an individual with a low cardiorespiratory fitness level than an individual with a high cardiorespiratory fitness level. The purpose of this study was to determine the association between moderate-intensity PA and fasting insulin levels and to examine possible differences in this association by race/ethnicity, central obesity, and cardiorespiratory fitness level.