The diurnal pattern of moderate-to-vigorous physical activity and obesity: a cross-sectional analysis.

OBJECTIVE: Moderate-to-vigorous physical activity (MVPA) is obesity-protective. However, the optimal time of the day to engage in MVPA for weight management is controversial. This study is designed to investigate the influence of the diurnal pattern of MVPA on the association between MVPA and obesity. METHODS: A total of 5285 participants in the 2003 to 2006 National Health and Nutrition Examination Survey (NHANES) were cross-sectionally analyzed. The diurnal pattern of objectively measured MVPA was classified into three clusters by K-means clustering analysis: morning (n = 642); midday (n = 2456); and evening (n = 2187). The associations of MVPA level and the diurnal pattern with obesity were tested. RESULTS: A strong linear association between MVPA and obesity was found in the morning group, whereas a weaker curvilinear association between MVPA and obesity was observed in the midday and evening groups, respectively. Among those who met the physical activity guidelines, the adjusted means for BMI were 25.9 (95% CI: 25.2-26.6), 27.6 (95% CI: 27.1-28.1), and 27.2 (95% CI: 26.8-27.7) kg/m2 in the morning, midday, and evening groups, respectively, and for waist circumference were 91.5 (95% CI: 89.4-93.6), 95.8 (95% CI: 94.7-96.9), and 95.0 (95% CI: 93.9-96.1) cm, respectively. CONCLUSIONS: The diurnal pattern of MVPA influences the association between MVPA and obesity. The promising role of morning MVPA for weight management warrants further investigation.

Association of the time of day of peak physical activity with cardiovascular mortality: Findings from the UK Biobank study.

Cardiovascular physiology and pathophysiology display pronounced circadian rhythms. The study is designed to examine whether the time of day of physical activity is associated with cardiovascular mortality. We analyzed 94,489 UK Biobank adults with objectively measured physical activity, including 53,328 morning-type participants and 30,962 evening-type participants based on self-reported chronotypes. The time of day of peak physical activity was categorized using a machine learning algorithm: early morning (n = 18,477), late morning (n = 25,700), midday (reference) (n = 27,803), and night (n = 22,509). Hazard ratios of cardiovascular mortality were examined using the Cox proportional hazards model. During a median follow-up of 6.9 years (interquartile range, 6.3-7.4 years), we identified 629 cardiovascular deaths. The hazard of cardiovascular mortality was elevated in the early morning group (hazard ratio = 1.56, 95% Confidence Interval [1.23-1.98]) and night group (1.49, [1.18-1.88]) but not in the late morning group (1.21, [0.98-1.47]) compared to the referent midday group. In the chronotype-stratified analysis, the increased cardiovascular mortality in the morning group was only observed in the evening-type participants, while the increased cardiovascular mortality in the night group was only observed in the morning-type participants. In conclusion, optimizing the timing of peak physical activity according to cardiovascular circadian rhythms and individual chronotypes could be a potential therapeutic target that brings additional health benefits.

Time-of-day moderate-to-vigorous physical activity and all-cause mortality in individuals with type 2 diabetes.

There is no clear evidence for the best time of day for physical activity in benefitting health among individuals with type 2 diabetes. This study was aimed to examine whether there is an optimal time of day for physical activity to increase longevity. In this cohort study of 904 patients with type 2 diabetes, we fitted a Cox model with restricted cubic spline to examine the association of moderate-to-vigorous physical activity (MVPA) and time of day with all-cause mortality. Compositional data analysis was used to examine the association of time spent in sedentary behaviour (SB), light-intensity physical activity (LIPA), morning MVPA, and evening MVPA with all-cause mortality. MVPA was inversely associated with all-cause mortality in a curvilinear manner (P-value for nonlinearity<0.0001). The interaction between MVPA and time of day was not significant (P-value for interaction=0.11). Substituting evening MVPA with morning MVPA was not associated with appreciable changes in all-cause mortality. There is no evidence that the time of day moderates the association of MVPA with all-cause mortality. Patients with higher levels of MVPA had lower mortality regardless of the timing of MVPA. Patients with type 2 diabetes should engage in regular physical activity whenever possible.

The Association of Self-Reported Muscle-Strengthening Activities With Carotid Intima-Media Thickness in Older Adults: Cooper Center Longitudinal Study.

The purpose of the current investigation was to examine the cross-sectional associations of participation in muscle-strengthening activities (MSAs) with carotid intima-media thickness (CIMT) among older adults. The data are from 2,557 older adult participants enrolled in an observational cohort who reported no history of cardiovascular disease. MSA was determined using a questionnaire. Carotid ultrasound was performed to measure the CIMT of the common carotid artery bilaterally. Logistic regression models were constructed to estimate the association of MSA with CIMT after adjustment for potential confounders. The participants were aged 68.6 ± 7.0 years, and the majority were male (71.7%) and White (96.5%); 18% had abnormal CIMT. Meeting the physical activity guidelines for MSA was inversely associated with abnormal CIMT after adjustment for age and sex. However, this observed inverse relation became statistically null after further adjustment for cardiovascular disease risk factors, including aerobic physical activity.

The association of midlife cardiorespiratory fitness with later life carotid atherosclerosis: Cooper Center Longitudinal Study.

BACKGROUND AND AIMS: While numerous cross-sectional studies have demonstrated an inverse relationship between cardiorespiratory fitness (CRF) and carotid atherosclerosis in middle age, much less is known about the association of midlife CRF with carotid atherosclerosis in later life. METHODS: We studied 1094 participants, free of cardiovascular disease, who completed a maximal exercise test (GXT) for an objective measure of CRF between ages 40 and 59 and carotid ultrasound after the age of 59, with at least five years between studies. Carotid intima media thickness was measured. Assessments were also made regarding the presence of plaque and percent stenosis in four regions: common carotid, bulb, internal carotid and external carotid arteries. Multivariable logistic regression models were constructed to estimate the association of CRF with carotid artery disease. RESULTS: At the time of GXT and carotid scan, participants were aged 50.7 ±â€¯5.7 years and 69.3 ±â€¯6.4 years, respectively. Almost half of participants had high midlife CRF (48.6%); 41.3% and 10.1% had moderate and low CRF, respectively. Over a mean follow-up period of 18.6 ±â€¯8.5 years, the odds of having carotid artery disease in later life in the high CRF group was 0.50 (95% CI: 0.29-0.87) compared with the low CRF group. Each 1 MET increase in CRF was associated with 10% lower odds of having carotid artery disease (OR = 0.89, 95% CI: 0.80-0.98). CONCLUSIONS: Midlife CRF was inversely associated with carotid artery disease measured almost two decades later. This may represent a mechanistic link between high midlife CRF and reduced risk of stroke in later life.

Relation of C-reactive protein, fibrinogen, and cardiorespiratory fitness to risk of systemic hypertension in men.

We investigated the relation between inflammation and incident hypertension, independent of obesity, and tested the associations of cardiorespiratory fitness (fitness) and indexes of inflammation for the development of hypertension in 2,475 normotensive men. Inflammatory markers were C-reactive protein (CRP) and fibrinogen. Fitness was directly measured by peak oxygen uptake during sign/symptom-limited treadmill exercise testing to volitional fatigue; 266 men (10.7%) developed hypertension during an average of 4 years follow-up. After adjusting for potential confounding variables, the relative risk (RR) and 95% confidence interval (CI) for incident hypertension in those in the upper tertile versus lower tertile were 1.55 (95% CI 1.15 to 2.09) for CRP and 1.51 (95% CI 1.10 to 2.06) for fibrinogen. Although the association between fibrinogen and incident hypertension persisted after adjusting for body mass index (p = 0.049), the relation between CRP and incident hypertension was no longer statistically significant (p = 0.08). Fit men had a 27% decreased (RR 0.73, 95% CI 0.56 to 0.94) risk of incident hypertension compared with unfit men in a multivariable adjusted model. In the joint analysis, unfit men with upper CRP had 1.81 times (95% CI 1.21 to 2.70) and unfit men with upper fibrinogen had 2.03 times (95% CI 1.33 to 3.12) greater risks of incident hypertension compared with fit men with low CRP and fibrinogen, respectively. However, these risks did not significantly increase in fit men with upper CRP (RR 1.12, 95% CI 0.76 to 1.63) and fibrinogen (RR 1.26, 95% CI 0.86 to 1.85) groups. In conclusion, these results suggest that heightened levels of fibrinogen, but not CRP, are associated with incident hypertension, independent of body weight, and that high fitness attenuates the risk of incident hypertension across upper levels of inflammatory markers in men.

Effects of combined aerobic and resistance exercise on central arterial stiffness and gait velocity in patients with chronic poststroke hemiparesis.

OBJECTIVE: The effects of combined aerobic and resistance exercise training on central arterial stiffness and gait velocity in patients with chronic poststroke hemiparesis were investigated. DESIGN: Twenty-six patients with chronic poststroke hemiparesis were randomly assigned to either the combined aerobic and resistance exercise group (n = 14) or the control group (n = 12). The exercise intervention group received a combined aerobic and resistance exercise training (1 hr/day, three times/week for 16 wks), whereas the control group received usual care. Central arterial stiffness was determined by pulse wave velocity and augmentation index. Gait velocity was assessed using the 6-min walk test, 10-m walk test, and the Timed Up-and-Go test. RESULTS: Patients in the exercise intervention group had greater improvement of mean pulse wave velocity (P < 0.001), augmentation index (P = 0.048), and gait velocity (6-min walk test, P < 0.001; 10-m walk test, P < 0.001) than did patients in the control group. Patients in the exercise intervention group also had greater improvements in physical fitness component (grip strength, P < 0.001; muscular strength of upper and lower limbs, P < 0.027; flexibility, P < 0.001) when compared with control patients. CONCLUSIONS: The combined aerobic and resistance exercise program significantly reduced central arterial stiffness and increased gait velocity in patients with chronic poststroke hemiparesis.

Lifestyle Factors and Coronary Artery Calcification.

The effective prevention of cardiovascular disease (CVD) remains a global health challenge. Adopting a combined primary (prevention of the first episode of coronary heart disease or stroke) and primordial (prevention of the causal risk factors of CVD) prevention strategy is the best approach to prevent CVD. Most importantly, the primordial prevention strategy should in the first place be to promote cardiovascular health across individual and population levels by improving the underlying causal risk factors for CVD (i.e., unhealthy diets, physical inactivity, obesity, and cigarette smoking). Epidemiological evidence indicates that maintaining favorable underlying risk factors (lifestyle factors) is associated with a lower risk of incident CVD. Prevention of early atherosclerotic vascular disease is also an important strategy to prevent CVD. However, there has been limited research on the association between lifestyle factors and early atherosclerotic vascular disease (i.e., coronary or carotid atherosclerosis) across race and gender groups in population-based studies. This article briefly reviews whether lifestyle factors relate to subclinical atherosclerosis as assessed by coronary artery calcification in asymptomatic individuals.

A prospective study of fasting plasma glucose and risk of stroke in asymptomatic men.

OBJECTIVE: To examine the association between levels of fasting plasma glucose (FPG) and incidence of stroke outcomes in a large cohort of asymptomatic men. PATIENTS AND METHODS: Participants were 43,933 men (mean ± SD age, 44.3 ± 9.9 years) who were free of known cardiovascular disease at baseline and whose FPG levels were assessed during a preventive medical examination at the Cooper Clinic, Dallas, TX, between January 7, 1971, and March 11, 2002. Patients with diagnosed diabetes mellitus (DM) or low FPG (<80 mg/dL [to convert to mmol/L, multiply by 0.0555]) were excluded. Fatal stroke was identified through the National Death Index, and nonfatal stroke was ascertained from mail-back surveys. RESULTS: A total of 595 stroke events (156 fatal and 456 nonfatal strokes; 17 men reported a nonfatal stroke before they died of stroke) occurred during 702,928 person-years of exposure. Age-adjusted fatal, nonfatal, and total stroke event rates per 10,000 person-years for normal FPG (80-109 mg/dL), impaired fasting glucose (110-125 mg/dL), and undiagnosed DM (≥ 126 mg/dL) were 2.1, 3.4, and 4.0 (P(trend)=.002); 10.3, 11.8, and 18.0 (P(trend)=.008); and 8.2, 9.6, and 12.4 (P(trend)=.008), respectively. After further adjusting for potential confounders, the direct association between FPG and fatal, nonfatal, or total stroke events remained significant (P(trend)=.02, .03, and .01, respectively). For FPG levels of 110 mg/dL or greater, each 10-unit increment of FPG was associated with a 6% higher risk of total stroke events (P=.05). CONCLUSION: Hyperglycemia (FPG, ≥ 110 mg/dL), even below the DM threshold (such as with impaired fasting glucose), was associated with a higher risk of fatal, nonfatal, or total stroke events in asymptomatic men.

Combined impact of lifestyle factors on cancer mortality in men.

PURPOSE: The impact of lifestyle factors on cancer mortality in the U.S. population has not been thoroughly explored. We examined the combined effects of cardiorespiratory fitness, never smoking, and normal waist girth on total cancer mortality in men. METHODS: We followed a total of 24,731 men ages 20-82 years who participated in the Aerobics Center Longitudinal Study. A low-risk profile was defined as never smoking, moderate or high fitness, and normal waist girth, and they were further categorized as having 0, 1, 2, or 3 combined low-risk factors. RESULTS: Over an average of 14.5 years of follow-up, there were a total of 384 cancer deaths. After adjustment for age, examination year, and multiple risk factors, men who were physically fit, never smoked, and had a normal waist girth had a 62% lower risk of total cancer mortality (95% confidence interval [CI], 45%-73%) compared with men with no low-risk factors. Men with all 3 low-risk factors had a 12-year (95% CI, 8.6-14.6) longer life expectancy compared with men with no low-risk factors. Approximately 37% (95% CI, 17%-52%) of total cancer deaths might have been avoided if the men had maintained all 3 low-risk factors. CONCLUSIONS: Being physically fit, never smoking, and maintaining a normal waist girth is associated with lower risk of total cancer mortality in men.

Effects of Panax ginseng supplementation on muscle damage and inflammation after uphill treadmill running in humans.

The purpose of this investigation was to determine whether Panax ginseng extract intake would influence exercise-induced muscle damage and inflammation responses. Eighteen male college students were randomly assigned to either an RG intake group (RG, n = 9) or a placebo group (P, n = 9). All subjects performed a high-intensity uphill treadmill running task (two rounds of 45 min at 10 km/h speed with a 15 degree uphill slope separated by 5 min of rest). The RG group ingested 20 g/day of Korean red ginseng extract (mixed with 200 ml of water) three times/day for seven days prior to performing the uphill treadmill exercise test and for four days after the treadmill test, while the P group ingested 200 ml of water containing Agastachis Herba on the same schedule. Plasma creatine kinase activity (CK) and interlukin-6 (IL-6) levels were measured at pre-exercise and 24, 48, 72, and 96 h post-exercise; the IL-6 level was also measured at 1 and 2 h post-exercise. To evaluate insulin sensitivity, the oral glucose tolerance test (OGTT) was performed 24 h post-exercise. Plasma CK level in RG was significantly lower than that in P 72 h post-exercise (p < 0.05), and IL-6 level was significantly decreased in RG during the 2 h and 3 h recovery period compared to that of P (p < 0.05). Plasma glucose and insulin responses in RG were significantly reduced compared to those of P (p < 0.05). The results of this study suggest that RG supplementation could reduce exercise-induced muscle damage and inflammatory responses, resulting in improvements in insulin sensitivity.

Protective health factors and incident hypertension in men.

BACKGROUND: Few studies have examined the association between a combination of lifestyle factors and the incidence of hypertension, particularly among men. This is important as lifestyle factors are often interrelated, and may often occur in combination. Thus, we investigated the individual and combined effects of body mass index (BMI), smoking status, alcohol intake, physical activity (PA), and cardiorespiratory fitness (CRF) on the incidence of hypertension in men. METHODS: A total of 14,568 men (mean age = 44.0 + or - 9.3 years) from the Aerobics Center Longitudinal Study (ACLS) initially free of hypertension completed an extensive baseline examination during 1974-2003, and were followed for the incidence of hypertension. RESULTS: A total of 1,959 men reported having hypertension during a mean of 10.7 + or - 7.6 years of follow-up. Our data indicated that a combination of five protective health factors significantly reduced the risk of hypertension by 47% (95% confidence interval (CI): 36-56%). We also found that whether all participants in our sample had five protective health factors, the incidence of hypertension would be expected to decrease by 29% (95% CI: 26-31%). Additionally, having a normal BMI and being a nonsmoker and physically fit were significantly and independently associated with a lower risk of developing hypertension. CONCLUSIONS: Our results show that among men aged 20-82 years, a healthy lifestyle can significantly reduce the risk of developing hypertension, and should be considered for the prevention of this chronic condition.

Effect of positive health factors and all-cause mortality in men.

PURPOSE: Although several health-related factors are independently associated with diverse health outcomes, their combined affect on mortality has not been fully described. METHODS: We examined the combined effect of several positive health factors, including having normal weight (body mass index = 18.5-24.9 kg.m), not smoking (not current smoker), consuming a moderate alcohol intake (1-14 drinks per week), being physically active (moderate to high level), and having a higher cardiorespiratory fitness (top two-thirds), on all-cause mortality in 38,110 men aged 20-84 yr from the Aerobics Center Longitudinal Study. RESULTS: There were 2642 deaths during an average of 16 yr of follow-up. Compared with men with zero positive health factors, the multivariable-adjusted hazard ratios (HR) of all-cause mortality with one, two, three, four, and five positive health factors were 0.78 (95% confidence interval (CI) = 0.64-0.95), 0.61 (95% CI = 0.50-0.73), 0.54 (95% CI = 0.44-0.65), 0.43 (95% CI = 0.35-0.52), and 0.39 (95% CI = 0.31-0.48), respectively (P for trend <0.001). The combination of five positive health factors accounted for 29% (95% CI = 14%-40%) of population-attributable risk for all-cause mortality. CONCLUSIONS: Our findings suggest that targeting more of these modifiable health factors may provide substantial health benefits in middle-aged men.

Influence of cardiorespiratory fitness on lung cancer mortality.

PURPOSE: Previous studies have suggested that higher levels of physical activity may lower lung cancer risk; however, few prospective studies have evaluated lung cancer mortality in relation to cardiorespiratory fitness (CRF), an objective marker of recent physical activity habits. METHODS: Thirty-eight thousand men, aged 20-84 yr, without history of cancer, received a preventive medical examination at the Cooper Clinic in Dallas, Texas, between 1974 and 2002. CRF was quantified as maximal treadmill exercise test duration and was grouped for analysis as low (lowest 20% of exercise duration), moderate (middle 40%), and high (upper 40%). RESULTS: A total of 232 lung cancer deaths occurred during follow-up (mean = 17 yr). After adjustment for age, examination year, body mass index, smoking, drinking, physical activity, and family history of cancer, hazard ratios (95% confidence intervals) for lung cancer deaths across low, moderate, and high CRF categories were 1.0, 0.48 (0.35-0.67), and 0.43 (0.28-0.65), respectively. There was an inverse association between CRF and lung cancer mortality in former (P for trend = 0.005) and current smokers (P for trend < 0.001) but not in never smokers (trend P = 0.14). Joint analysis of smoking and fitness status revealed a significant 12-fold higher risk of death in current smokers (hazard ratio = 11.9, 95% confidence interval = 6.0-23.6) with low CRF as compared with never smokers who had high CRF. CONCLUSIONS: Although the potential for some residual confounding by smoking could not be eliminated, these data suggest that CRF is inversely associated with lung cancer mortality in men. Continued study of CRF in relation to lung cancer, particularly among smokers, may further our understanding of disease etiology and reveal additional strategies for reducing its burden.

Combined effects of cardiorespiratory fitness, not smoking, and normal waist girth on morbidity and mortality in men.

BACKGROUND: Physical inactivity, cigarette smoking, and abdominal obesity are key modifiable risk factors for coronary heart disease (CHD). We investigated the combined effects of not having these risk factors on CHD events and cardiovascular disease (CVD) and all-cause mortality in men. METHODS: We followed up 23 657 men, aged 30 to 79 years, who completed a medical evaluation including a maximal treadmill exercise test and self-reported health habits. A low-risk profile was defined as not smoking, moderate or high fitness, and normal waist girth. There were 482 CHD events (nonfatal myocardial infarction or fatal CHD) and 1034 deaths (306 CVD, 387 cancers, and 341 others) during a mean 14.7 years of follow-up (348 811 man-years). RESULTS: After adjustment for age, examination year, and multiple baseline risk factors, there was an inverse association between a greater number of low-risk factors and CHD events, and CVD and all-cause mortality in men (P value for trend, <.001 for all). Men with a normal waist girth and who were physically fit and not smoking had a 59% lower risk of CHD events (95% confidence interval [CI], 39%-72%), a 77% lower risk of CVD mortality (95% CI, 65%-85%), and a 69% lower risk of all-cause mortality (95% CI, 60%-76%) compared with men with none of these low-risk factors. Men with 0 compared with 3 low-risk factors had a shorter life expectancy by 14.2 years (95% CI, 12.2-15.9 years). CONCLUSION: Being physically fit, not smoking, and maintaining a normal waist girth is associated with lower risk of CHD events, and CVD and all-cause mortality in men.

Cardiorespiratory fitness and coronary artery calcification in young adults: The CARDIA Study.

Whether cardiorespiratory fitness relates to early subclinical atherosclerotic vascular disease remains unknown. We investigated the relation of cardiorespiratory fitness to coronary artery calcification (CAC) in 2373 African-American and White young adults from the Coronary Artery Risk Development in Young Adults (CARDIA) Study. We measured cardiorespiratory fitness in 1985-1986 (baseline) using a symptom-limited exercise test on a treadmill. Coronary calcium scores were measured in 2001-2002 (year 15) using electron-beam or multi-detector computed tomography. CAC was classified as present or absent, while cardiorespiratory fitness was classified as sex-specific low, moderate, and high fitness categories. After adjustment for age, sex, race, clinical center, education, cigarette smoking, waist girth, alcohol intake, physical activity, systolic blood pressure, antihypertensive medication use, diabetes mellitus, and fasting insulin, baseline cardiorespiratory fitness was inversely associated with prevalence of CAC in young adults (P for trend=0.03). The odds ratios of having CAC for persons in the moderately and highly fit individuals were 0.80 (95% confidence interval (CI), 0.55-1.15) and 0.59 (95% CI, 0.36-0.97), respectively, as compared with the low-fit individuals. High levels of cardiorespiratory fitness were associated with a lower risk of having coronary calcification 15 years later in African-American and White young adults.

Effects of 4 weeks recombinant human growth hormone administration on insulin resistance of skeletal muscle in rats.

PURPOSE: Effect of recombinant human growth hormone (rhGH) administration on lipid storage, and its subsequent effect on insulin sensitivity have not yet been adequately examined. Thus, we investigated the effects of rhGH treatment on muscle triglyceride (TG) and ceramide content, and insulin sensitivity after 4 weeks of rhGH administration in rats. MATERIALS AND METHODS: Fourteen rats were randomly assigned to two groups: rhGH injection group (GH, n = 7) and saline injection group (CON, n = 7). GH received rhGH by subcutaneous injections (130 microg.kg(-1).day(-1), 6 days.week(-1)) for 4 weeks, while CON received saline injections that were equivalent in volume to GH group. Intramuscular TG and ceramide content and hepatic TG content were measured. To determine insulin sensitivity, oral glucose tolerance test (OGTT) and muscle incubation for glucose transport rate were performed in rats, and used as indicators of insulin sensitivity. We also examined plasma lipid profiles. RESULTS: After 4 weeks of rhGH treatment, the GH group had higher muscle and liver TG contents than the CON (p < 0.05). Ceramide content in GH was significantly greater than that in CON (p < 0.05). GH also had higher plasma levels of FFA (p < 0.05), glucose and insulin responses during OGTT (p < 0.05), and lower glucose transport rates in submaximal insulin concentration (p < 0.05) as compared with CON. Results indicate that rhGH treatment is associated with insulin resistance in rats. CONCLUSION: rhGH treatment elevated muscle TG and ceramide content, and hepatic TG content. Thus, elevation of these compounded by rhGH treatment could contribute to the development of insulin resistance in rats.

Body size satisfaction and physical activity levels among men and women.

Body size satisfaction may be an important factor associated with physical activity. We analyzed data from the 2002 National Physical Activity and Weight Loss Survey (NPAWLS), a population-based cross-sectional telephone survey of US adults. Multiple logistic regression models were used to examine the association of body size satisfaction on being regularly active. Participants were aged > or =18 years with complete data on weight, race/ethnicity, physical activity level, and body size satisfaction (n = 10,021). More than half of men (55.8%) and women (53.3%) who reported being very satisfied with the body size were regularly active. After adjustment for covariates, participants who reported being somewhat or not satisfied with their body size had a 13 and 44% lower odds of being regularly active, respectively, compared with those very satisfied with their body size. When stratified by race/ethnicity, this association remained in whites (P for trend <0.001), but became weaker and nonsignificant in blacks, Hispanics, or other racial/ethnic groups. Irrespective of actual weight, those who were satisfied with their body size were more likely to engage in regular physical activity than those less satisfied. Further research is needed to explore predictors of physical activity to reduce health disparities.

A prospective study of cardiorespiratory fitness and risk of type 2 diabetes in women.

OBJECTIVE: The purpose of this study was to determine the independent and joint associations of cardiorespiratory fitness (CRF) and BMI with the incidence of type 2 diabetes in women. RESEARCH DESIGN AND METHODS: An observational cohort of 6,249 women aged 20-79 years was free of baseline cardiovascular disease, cancer, and diabetes. CRF was measured using a maximal treadmill exercise test. BMI was computed from measured height and weight. The incidence of type 2 diabetes was identified primarily by 1997 American Diabetes Association criteria. RESULTS: During a 17-year follow-up, 143 cases of type 2 diabetes occurred. Compared with the least fit third, the multivariate (including BMI)-adjusted hazard ratio (HR) (95% CI) was 0.86 (0.59-1.25) for the middle third and 0.61 (0.38-0.96) for the upper third of CRF. For BMI, the multivariate (including CRF)-adjusted HR (95% CI) was 2.34 (1.55-3.54) for overweight individuals and 3.70 (2.12-6.44) for obese individuals, compared with normal-weight patients. In the combined analyses, overweight/obese unfit (the lowest one-third of CRF) women had significantly higher risks compared with normal-weight fit (the upper two-thirds of CRF) women. CONCLUSIONS: Low CRF and higher BMI were independently associated with incident type 2 diabetes. The protective effect of CRF was observed in individuals who were overweight or obese, but CRF did not eliminate the increased risk in these groups. These findings underscore the critical importance of promoting regular physical activity and maintaining normal weight for diabetes prevention.

Abdominal obesity and coronary artery calcification in young adults: the Coronary Artery Risk Development in Young Adults (CARDIA) Study.

BACKGROUND: Whether abdominal obesity is related to coronary artery calcification (CAC) is not known. OBJECTIVE: We investigated the relations of waist girth and waist-hip ratio (WHR) to CAC in 2951 African American and white young adults from the Coronary Artery Risk Development in Young Adults Study. DESIGN: The present study was a cross-sectional and observational cohort study. Using standardized protocols, we measured CAC in 2001-2002 by using computed tomography and measured waist and hip girths in 1985-1986 (baseline), 1995-1996 (year 10), and 2001-2002 (year 15, waist girth only). CAC was classified as present or absent, whereas waist girth and WHR were placed in sex-specific tertiles. RESULTS: After adjustment for age, sex, race, clinical center, physical activity, cigarette smoking, education, and alcohol intake, baseline waist girth and WHR were directly associated with a higher prevalence of CAC 15 y later (P for trend < 0.001 for both). The odds ratios (ORs) for CAC in the highest versus lowest tertiles of waist girth and WHR were 1.9 (95% CI: 1.36, 2.65) and 1.7 (1.23, 2.41), respectively. Waist girth and WHR at year 10 and waist girth at year 15 similarly predicted CAC. These associations persisted after additional adjustment for systolic blood pressure, fasting insulin concentrations, diabetes, and antihypertensive medication use but became nonsignificant after additional adjustment for blood lipids. CONCLUSIONS: Abdominal obesity measured by waist girth or WHR is associated with early atherosclerosis as measured by the presence of CAC in African American and white young adults. This is consistent with an involvement of visceral fat in the occurrence of coronary artery calcium in young adults.