Changes in plasma lipids and lipoproteins in overweight men during weight loss through dieting as compared with exercise

Prestroke physical activity and early functional status after stroke

BACKGROUND

The importance of physical activity as a modifiable risk factor for stroke in particular and cardiovascular disease in general is well documented. The effect of exercise on stroke severity and stroke outcomes is less clear. This study aimed to assess that effect.

METHODS

Data collected for patients enrolled in the Ischemic Stroke Genetics Study were reviewed for prestroke self-reported levels of activity and four measures of stroke outcome assessed at enrollment and approximately 3 months after enrollment. Logistic regression was used to assess the association between physical activity and stroke outcomes, unadjusted and adjusted for patient characteristics.

RESULTS

A total of 673 patients were enrolled; 50.5% reported aerobic physical activity less than once a week, 28.5% reported aerobic physical activity one to three times weekly, and 21% reported aerobic physical activity four times a week or more. Patients with moderate and high levels of physical activity were more likely to have higher Barthel Index (BI) scores at enrollment. A similar association was detected for exercise and good outcomes for the Oxford Handicap Scale (OHS). After 3 months of follow-up, moderate activity was still associated with a high BI score. No significant association was detected for activity and the OHS or Glasgow Outcome Scale at follow-up after adjustment for patient characteristics.

CONCLUSIONS

Higher levels of self-reported prestroke physical activity may be associated with functional advantages after stroke. Our findings should be seen as exploratory, requiring confirmation, ideally in a longitudinal study of exercise in an older population.

High-density lipoprotein-cholesterol trajectory pattern, associated lifestyle and biochemical factors among Taiwanese

BACKGROUND

Little is known about high-density lipoprotein-cholesterol (HDL-C) trajectory patterns among ethnic Chinese in Taiwan, or the effects of lifestyle and biochemical measurements on these trajectory patterns.

METHODS AND RESULTS

This longitudinal study was based on 330 adult participants who underwent biochemical measurements annually from 2003 to 2006. As time progressed, HDL-C increased significantly; women had a consistently higher value (10 mg/dl) than men. An increase of 1 kg/m(2) in body mass index was associated with -1.00 +/-0.25 mg/dl HDL-C for women (P=0.0001) and -0.78 +/-0.11 mg/dl for men (P<0.0001). Current smoking was inversely associated with HDL-C in men only. Systolic blood pressure and exercise frequency were positively associated with HDL-C in men only. Compared with non-smokers, participants who smoked had a lower HDL-C level of -8.42 +/-4.90 mg/dl in women (P=0.09) and -3.60 +/-0.94 mg/dl in men (P=0.0001). In contrast, a 1-h increase in exercise frequency every week was related to an increased HDL-C level of 0.38 +/-0.28 mg/dl for women (P=0.18) and 0.53 +/-0.14 mg/dl for men (P=0.0001).

CONCLUSIONS

An increase in HDL-C was shown over a 4-year period and gender-specific lifestyle factors were associated with HDL-C concentration among ethnic Chinese in Taiwan.

Caloric restriction alone and with exercise improves CVD risk in healthy non-obese individuals

Calorie restriction (CR) delays the development of age-associated disease and increases lifespan in rodents, but the effects in humans remain uncertain.

PURPOSE

Determine the effect of 6 months of CR with or without exercise on cardiovascular disease (CVD) risk factors and estimated 10-year CVD risk in healthy non-obese men and women.

METHODS

Thirty-six individuals were randomized to one of three groups for 6 months: Control, 100% of energy requirements; CR, 25% calorie restriction; CR+EX, 12.5% CR+12.5% increase in energy expenditure via aerobic exercise. CVD risk factors were assessed at baseline, 3 and 6 months.

RESULTS

After 6 months, CR and CR+EX lost approximately 10% of body weight. CR significantly reduced triacylglycerol (-31+/-15mg/dL) and factor VIIc (-10.7+/-2.3%). Similarly CR+EX reduced triacylglycerol (-22+/-8mg/dL) and additionally reduced LDL-C (-16.0+/-5.1mg/dL) and DBP (-4.0+/-2.1mmHg). In contrast, both triacylglycerol (24+/-14mg/dL) and factor VIIc (7.9+/-2.3%) were increased in the Control group. HDL-cholesterol was increased in all groups while hsCRP was lower in the Controls versus CR+EX. Estimated 10-year CVD risk significantly declined from baseline by 29% in CR (P<0.001) and 38% in the CR+EX (P<0.001) while remaining unchanged in the Control group.

CONCLUSIONS

Based on combined favorable changes in lipid and blood pressure, caloric restriction with or without exercise that induces weight loss favorably reduces risk for CVD even in already healthy non-obese individuals.

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.

Effect of rimonabant on the high-triglyceride/ low-HDL-cholesterol dyslipidemia, intraabdominal adiposity, and liver fat: the ADAGIO-Lipids trial

BACKGROUND

Rimonabant, the first selective cannabinoid type 1 (CB1) receptor antagonist, improves cardiometabolic risk factors in overweight/obese patients. ADAGIO-Lipids assessed the effect of rimonabant on cardiometabolic risk factors and intraabdominal and liver fat.

METHODS AND RESULTS

803 abdominally obese patients with atherogenic dyslipidemia (increased triglycerides [TG] or reduced high-density lipoprotein-cholesterol [HDL-C]) were randomized to placebo or rimonabant 20 mg/d for 1 year. HDL-C and TG were coprimary end points. Intraabdominal (visceral) and liver fat were measured by computed tomography in a subgroup of 231 patients. In total, 73% of rimonabant- and 70% of placebo-treated patients completed the study treatment. Rimonabant 20 mg produced significantly greater changes from baseline versus placebo in HDL-C (+7.4%) and TG levels (-18%; P<0.0001), as well as low-density lipoprotein (LDL) and HDL particle sizes, apolipoprotein A1 and B, HDL2, HDL3, C-reactive protein, and adiponectin levels (all P<0.05). Rimonabant decreased abdominal subcutaneous adipose tissue (AT) cross-sectional area by 5.1% compared to placebo (P<0.005), with a greater reduction in visceral AT (-10.1% compared to placebo; P<0.0005), thereby reducing the ratio of visceral/subcutaneous AT (P<0.05). Rimonabant significantly reduced liver fat content (liver/spleen attenuation ratio; P<0.005). Systolic (-3.3 mm Hg) and diastolic (-2.4 mm Hg) blood pressure were significantly reduced with rimonabant versus placebo (P<0.0001). The safety profile of rimonabant was consistent with previous studies; gastrointestinal, nervous system, psychiatric, and general adverse events were more common with rimonabant 20 mg.

CONCLUSIONS

In abdominally obese patients with atherogenic dyslipidemia, rimonabant 20 mg significantly improved multiple cardiometabolic risk markers and induced significant reductions in both intraabdominal and liver fat.

Lifestyle and pharmacological approaches to weight loss: efficacy and safety

CONTEXT

Obesity results from a prolonged small positive energy balance, and its treatment needs to reverse this imbalance.

EVIDENCE ACQUISITION

Citations retrieved from PubMed and The Handbook of Obesity 2008 were selected to illustrate the points.

EVIDENCE SYNTHESIS

Many different diets have been tried to treat obesity, and weight loss occurs with all of them. There is currently no evidence that clearly supports a superiority of one macronutrient composition for diets used for weight loss. The principal effect seems to be the degree of adherence to the prescribed calorie reduction. Lifestyle strategies to modify eating behavior can be used in individual counseling sessions or in groups, both of which are important in helping patients modify their patterns of eating. Physical activity is particularly important in helping patients maintain a weight loss once achieved and is less valuable for weight loss itself. Food intake is controlled through many different mechanisms, but only a few drugs have been developed that tap these mechanisms. Orlistat, which blocks intestinal lipase, is one; sibutramine, a serotonin-norepinephrine reuptake inhibitor, is a second. Surgical approaches provide the most dramatic weight loss and have been demonstrated to reduce long-term mortality and reduce the incidence of diabetes.

CONCLUSIONS

Weight loss can be achieved by many methods, but the surgical procedures appear to be the most durable.

High density lipoprotein cholesterol: an evolving target of therapy in the management of cardiovascular disease

Since the pioneering work of John Gofman in the 1950s, our understanding of high density lipoprotein cholesterol (HDL-C) and its relationship to coronary heart disease (CHD) has grown substantially. Numerous clinical trials since the Framingham Study in 1977 have demonstrated an inverse relationship between HDL-C and one’s risk of developing CHD. Over the past two decades, preclinical research has gained further insight into the nature of HDL-C metabolism, specifically regarding the ability of HDL-C to promote reverse cholesterol transport (RCT). Recent attempts to harness HDL’s ability to enhance RCT have revealed the complexity of HDL-C metabolism. This review provides a detailed update on HDL-C as an evolving therapeutic target in the management of cardiovascular disease.

Implications of the obesity epidemic for lipid-lowering therapy: non-HDL cholesterol should replace LDL cholesterol as the primary therapeutic target

Obesity, metabolic syndrome and diabetes are conditions with increasing prevalence around the world. Cardiovascular risk in diabetics is often so high as to overlap with event rates observed in those with established coronary disease and this has lead to diabetes being classified as a coronary risk equivalent. However, despite the elevated risk of cardiovascular events associated with diabetes and the metabolic syndrome, these patients often have normal low density lipoprotein (LDL) cholesterol despite frequent increases in apolipoprotein B, triglycerides and nonhigh density lipoprotein (HDL) cholesterol. In contrast to LDL cholesterol, non-HDL cholesterol represents cardiovascular risk across all patient populations but is currently only recommended as a secondary target of therapy by the ATP III report for patients with hypertriglyceridemia. This article provides an overview of the studies that shown non-HDL cholesterol to be superior to LDL cholesterol in predicting cardiovascular events and presents the case for non-HDL cholesterol being the more appropriate primary target of therapy in the context of the obesity pandemic. Adopting non-HDL cholesterol as the primary therapeutic target for all patients will conceivably lead to an appropriate intensification of therapy for high risk patients with low LDL cholesterol.

Weight loss during the intensive intervention phase of the weight-loss maintenance trial

BACKGROUND

To improve methods for long-term weight management, the Weight Loss Maintenance (WLM) trial, a four-center randomized trial, was conducted to compare alternative strategies for maintaining weight loss over a 30-month period. This paper describes methods and results for the initial 6-month weight-loss program (Phase I).

METHODS

Eligible adults were aged > or =25, overweight or obese (BMI=25-45 kg/m2), and on medications for hypertension and/or dyslipidemia. Anthropomorphic, demographic, and psychosocial measures were collected at baseline and 6 months. Participants (n=1685) attended 20 weekly group sessions to encourage calorie restriction, moderate-intensity physical activity, and the DASH (dietary approaches to stop hypertension) dietary pattern. Weight-loss predictors with missing data were replaced by multiple imputation.

RESULTS

Participants were 44% African American and 67% women; 79% were obese (BMI> or =30), 87% were taking anti-hypertensive medications, and 38% were taking antidyslipidemia medications. Participants attended an average of 72% of 20 group sessions. They self-reported 117 minutes of moderate-intensity physical activity per week, kept 3.7 daily food records per week, and consumed 2.9 servings of fruits and vegetables per day. The Phase-I follow-up rate was 92%. Mean (SD) weight change was -5.8 kg (4.4), and 69% lost at least 4 kg. All race-gender subgroups lost substantial weight: African-American men (-5.4 kg +/- 7.7); African-American women (-4.1 kg +/- 2.9); non-African-American men (-8.5 kg +/- 12.9); and non-African-American women (-5.8 kg +/- 6.1). Behavioral measures (e.g., diet records and physical activity) accounted for most of the weight-loss variation, although the association between behavioral measures and weight loss differed by race and gender groups.

CONCLUSIONS

The WLM behavioral intervention successfully achieved clinically significant short-term weight loss in a diverse population of high-risk patients.

Prospective study of incident age-related macular degeneration in relation to vigorous physical activity during a 7-year follow-up

PURPOSE

To test whether the risk of age-related macular degeneration (AMD) decreases with vigorous physical activity.

METHODS

This was a prospective study of self-reported clinically diagnosed macular degeneration in male (n = 29,532) and female (n = 12,176) runners followed prospectively for 7.7 years. Survival analyses of incident AMD versus average running distance (kilometers per day), cardiorespiratory fitness (10-km footrace performance), body mass index (BMI), cigarette use, and diet at baseline.

RESULTS

The 110 men and 42 women reporting incident AMD were older than those unaffected (mean +/- SE: 54.81 +/- 0.97 vs. 44.86 +/- 0.06 years), and the men were significantly more likely to have once smoked cigarettes (50.6 vs. 41.2%, P = 0.04 when adjusted for age). Age- and sex-adjusted AMD risk was greater in the men and women who consumed more meat (3.17 +/- 0.20 vs. 2.55 +/- 0.02 servings/wk) and less fruit (9.41 +/- 0.70 vs. 10.92 +/- 0.05 pieces/wk). The men and women reporting incident AMD ran for exercise significantly less than those who remained unaffected, when adjustment was made for age and sex (4.57 +/- 0.30 vs. 5.34 +/- 0.02 km/d, P < or = 0.01). When adjusted for age, sex, diet, and smoking history, the relative risk for AMD decreased 10% per km/d increment in running distance. Moreover, compared with the men and women who averaged less than 2 km/d, those averaging 2 to 4 km/d had 19% lower adjusted risk, and those averaging > or = 4 km/d had 42% to 54% lower adjusted AMD risk.

CONCLUSIONS

Higher doses of vigorous exercise (running) are associated with lower incident AMD risk independent of weight, cardiorespiratory fitness, and cigarette use. Limitations of the analyses include the select nature of the sample and reliance on self-report of both running history and clinically diagnosed AMD.

The role of physical activity in maintaining a reduced weight

Current physical activity recommendations call for 30 minutes of moderate-intensity activity on most days of the week, or the equivalent of expending approximately 1000 kcal in activity per week. These recommendations were formulated based on reducing the risk for chronic disease, but they do not appear adequate for weight loss and maintenance. Data from epidemiologic studies and randomized trials indicate that closer to 60 to 90 minutes of moderate-intensity activity every day is required for maintaining a reduced body weight, equivalent to expending 2500 to 2800 kcal in activity per week. Relevant studies leading to this conclusion are reviewed in this manuscript. However, to make a dent in the prevalence of obesity by targeting physical activity and food intake, it is imperative to address the current "built" environment, which is conducive to a sedentary lifestyle and overconsumption of energy. Only then will rigorous activity recommendations be easier to implement.

Prospective epidemiological cohort study of reduced risk for incident cataract with vigorous physical activity and cardiorespiratory fitness during a 7-year follow-up

PURPOSE

To test whether greater vigorous physical activity (kilometers per week run) and greater cardiorespiratory fitness (10-km race performance in meters per second) reduce the incidence of clinically diagnosed cataract.

METHODS

Prospective cohort study of self-reported clinical diagnosis of cataract in nondiabetic, nonvegetarian, and nonsmoking male (n = 29,025) and female runners (n = 11,967).

RESULTS

Incident cataracts were reported by 733 (2.53%) men and 179 (1.50%) women during (mean +/- SE) 7.74 +/- 0.01 and 7.42 +/- 0.02 years of follow-up, respectively. The risk for incident cataract increased with BMI, such that the risk in men > 27.5 kg/m(2) was 88% larger than in men < 20 kg/m(2). Men's cataract risk declined significantly in relation to running distance (P = 0.01), even when adjusted for BMI. Men who ran > or = 64 km/wk had 35% lower risk for cataract than those reporting < 16 km/wk (28% lower risk when adjusted for BMI). In addition, men with greater cardiorespiratory fitness were at significantly less risk for development of cataract than were the least fit men. This result was not accounted for by adjustment for running distance or BMI. Compared with the least fit men, those who ran faster than 4.75 m/s had 50% lower risk for incident cataract (43% lower when adjusted for km/wk and BMI).

CONCLUSIONS

These data suggest that the men's cataract risk decreased in association with lower BMI, greater physical activity, and greater cardiorespiratory fitness, the latter being statistically independent of both BMI and physical activity. The study limitations include the absence of confirmation of the clinical diagnosis and the lack of specificity of the type of cataract.

A Review of TV Viewing and Its Association With Health Outcomes in Adults

Observational studies of the relationship between TV viewing and health outcomes (overweight/obesity, cholesterol/lipids, blood pressure/hypertension, type 2 diabetes, and metabolic syndrome) in adults are reviewed. Studies indicate that in adults, greater amounts of TV viewing are consistently associated with increased overweight risk, both cross-sectionally and longitudinally, but that results are mixed regarding the relationship between adult TV viewing and other health outcomes. It is theorized that greater TV viewing is related to increased weight status and poorer health outcomes by reducing energy expenditure, predominantly through reducing time spent in physical activity, and increasing energy intake. No randomized trials that manipulated TV viewing time measured the effects of this manipulation on diet and physical activity and then measured future health outcomes in adults. However, experimental studies, predominantly conducted in children, show relationships between TV viewing, energy intake, physical activity, and weight status, which follow the hypothesized mechanisms. Interventions targeting TV viewing in adults appear to be justified, and proposed methods for conducting these interventions, as well as potential barriers to implementing these interventions, are discussed.

Design considerations and rationale of a multi-center trial to sustain weight loss: the Weight Loss Maintenance Trial

BACKGROUND

The Weight Loss Maintenance Trial (WLM) is a multi-center, randomized, controlled trial that compares the effects of two 30-month maintenance interventions, i.e., Personal Contact (PC) and Interactive Technology (IT) to a self-directed usual care control group (SD), in overweight or obese individuals who are at high risk for cardiovascular disease.

PURPOSE

This paper provides an overview of the design and methods, and design considerations and lessons learned from this trial.

METHODS

All participants received a 6-month behavioral weight loss program consisting of weekly group sessions. Participants who lost 4 kg were randomized to one of three conditions (PC, IT, or SD). The PC condition provided monthly contacts with an interventionist primarily via telephone and quarterly face-to-face visits. The IT condition provided frequent, individualized contact through a tailored, website system. Both the PC and IT maintenance programs encouraged the DASH dietary pattern and employed theory-based behavioral techniques to promote maintenance.

RESULTS

Design considerations included choice of study population, frequency and type of intervention visits, and choice of primary outcome. Overweight or obese persons with CVD risk factors were studied. The pros and cons of studying this population while excluding others are presented. We studied intervention contact strategies that made fewer demands on participant time and travel, while providing frequent opportunities for interaction. The primary outcome variable for the trial was change in weight from randomization to end of follow-up (30 months).

LIMITATIONS

Limits to generalizability are discussed. Individuals in need of weight loss strategies may have been excluded due to barriers associated with internet use. Other participants may have been excluded secondary to a comorbid condition.

CONCLUSIONS

This paper highlights the design and methods of WLM and informs readers of discussions of critical issues and lessons learned from the trial.

Gender differences in predictors of body weight and body weight change in healthy adults

BACKGROUND

Overweight and obesity are important predictors of a wide variety of health problems. Analysis of naturally occurring changes in body weight can provide valuable insights in improving our understanding of the influence of demographic, lifestyle, and psychosocial factors on weight gain in middle-age adults.

OBJECTIVE

To identify gender-specific predictors of body weight using cross-sectional and longitudinal analyses.

METHODS AND PROCEDURES

Anthropometric, lifestyle and psychosocial factors were measured at baseline and then quarterly for 1 year in 572 healthy adult volunteers from Central Massachusetts who were recruited between 1994 and 1998. Linear mixed models were used to analyze the relationship between body weight and potential predictors, including demographic (e.g., age, educational level), lifestyle (e.g., diet, physical activity, smoking), and psychosocial (e.g., anxiety, depression) factors.

RESULTS

Over the 1-year study period, on average, men gained 0.3 kg and women lost 0.2 kg. Predictors of lower body weight at baseline in both men and women included current cigarette smoking, greater leisure-time physical activity, and lower depression and anxiety scores. Lower body weights were associated with a lower percentage of caloric intake from protein and greater occupational physical activity levels only among men; and with higher education level only among women. Longitudinal predictors of 1-year weight gain among women included increased total caloric intake and decreased leisure-time physical activity, and among men, greater anxiety scores.

DISCUSSION

Demographic, lifestyle and psychosocial factors are independently related to naturally occurring changes in body weight and have marked differential gender effects. These effects should be taken into consideration when designing interventions for weight-loss and maintenance at the individual and population levels.

Effect of obesity on high-density lipoprotein metabolism

Reduced levels of high-density lipoproteins (HDL) in non-obese and obese states are associated with increased risk for the development of coronary artery disease. Therefore, it is imperative to determine the mechanisms responsible for reduced HDL in obese states and, conversely, to examine therapies aimed at increasing HDL levels in these individuals. This paper examines the multiple causes for reduced HDL in obese states and the effect of exercise and diet--two non-pharmacologic therapies--on HDL metabolism in humans. In general, the concentration of HDL-cholesterol is adversely altered in obesity, with HDL-cholesterol levels associated with both the degree and distribution of obesity. More specifically, intra-abdominal visceral fat deposition is an important negative correlate of HDL-cholesterol. The specific subfractions of HDL that are altered in obese states include the HDL2, apolipoprotein A-I, and pre-beta1 subfractions. Decreased HDL levels in obesity have been attributed to both an enhancement in the uptake of HDL2 by adipocytes and an increase in the catabolism of apolipoprotein A-I on HDL particles. In addition, there is a decrease in the conversion of the pre-beta1 subfraction, the initial acceptor of cholesterol from peripheral cells, to pre-beta2 particles. Conversely, as a means of reversing the decrease in HDL levels in obesity, sustained weight loss is an effective method. More specifically, weight loss achieved through exercise is more effective at raising HDL levels than dieting. Exercise mediates positive effects on HDL levels at least partly through changes in enzymes of HDL metabolism. Increased lipid transfer to HDL by lipoprotein lipase and reduced HDL clearance by hepatic triglyceride lipase as a result of endurance training are two important mechanisms for increases in HDL observed from exercise.

Obesity in neurobiology

Obesity reflects an imbalance between energy uptake and expenditure that is mediated by behavior. Obesity is a growing epidemic and a major risk factor for neurobiological diseases like stroke, dementia, intracranial hypertension and sleep disorders. Conversely, obesity can also be induced by neurobiological disorders and drugs. The etiology of obesity is complex and includes biology, behavior and environment. Physicians are faced with the need to manage obesity while strategies for prevention and sustained weight reduction are limited. Present treatment options comprise lifestyle modification, diet, pharmacotherapy and bariatric surgery. Considerable headway has been made into elucidating the neurobiological underpinnings of obesogenic behavior. There is now a growing understanding of the metabolic, hormonal and behavioral circuitries that contribute to the complex and redundant system for energy balance. Changing the net balance of this system to prevent or reduce obesity requires multimodal and long-term interventions.

The role of physical activity in producing and maintaining weight loss

The majority of randomized, controlled trials (RCTs) show only modest weight loss with exercise intervention alone, and slight increases in weight loss when exercise intervention is added to dietary restriction. In most RCTs, the energy deficit produced by the prescribed exercise is far smaller than that usually produced by dietary restriction. In prospective studies that prescribed high levels of exercise, enrolled individuals achieved substantially greater weight loss-comparable to that obtained after similar energy deficits were produced by caloric restriction. High levels of exercise might, however, be difficult for overweight or obese adults to achieve and sustain. RCTs examining exercise and its effect on weight-loss maintenance demonstrated mixed results; however, weight maintenance interventions were usually of limited duration and long-term adherence to exercise was problematic. Epidemiologic, cross-sectional, and prospective correlation studies suggest an essential role for physical activity in weight-loss maintenance, and post hoc analysis of prospective trials shows a clear dose-response relationship between physical activity and weight maintenance. This article reviews the role of physical activity in producing and maintaining weight loss. We focus on prospective, RCTs lasting at least 4 months; however, other prospective trials, meta-analyses and large systematic reviews are included. Limitations in the current body of literature are discussed.

Weight-related increases in hypertension, hypercholesterolemia, and diabetes risk in normal weight male and female runners

BACKGROUND

Although 36% of US men and 42% of US women are of normal weight, the health implications of greater weight in ostensibly normal-weight individuals are seldom acknowledged.

METHODS AND RESULTS

Self-reported physician-diagnosed incident diabetes, high cholesterol, and hypertension were compared with adult body mass index (BMI), and body circumferences in 29,139 male and 11,985 female nonsmoking runners followed prospectively for 7.7 and 7.4 years, respectively. Included among these were 20,731 men and 11,197 women who were of normal weight at baseline (BMI < 25 kg/m2). During follow-up, 2342 men (8.53%) and 499 women (4.26%) became hypertensive, 3330 men (12.2%) and 599 women (5.14%) were diagnosed with high cholesterol, and 197 men (0.68%) and 28 women (0.23%) became diabetic. Increasing BMI and waist circumference at baseline significantly increased the log odds for normal-weight men becoming hypertensive (P<0.0001), hypercholesterolemic (P<0.0001), and diabetic (P<0.02), and for normal-weight women becoming hypertensive (P=0.05). The log odds for being diagnosed with high cholesterol also increased with baseline BMI in normal-weight women (P<0.05). Relative to men with BMI < 20 kg/m2, the odds for being diagnosed with hypertension or high cholesterol increased by 45% (P=0.05) and 64% (P=0.002), respectively, for those with 20 < or = BMI < 22.5 kg/m2, and by 121% (P<0.0001) and 135% (P<0.0001), respectively, for those with 22.5 < or = BMI < 25 kg/m2. The odds for women with 22.5 < or = BMI < 25 kg/m2 developing hypertension or high cholesterol were 33% (P=0.02) and 29% (P=0.03) higher, respectively, than for women with 20 < or = BMI < 22.5 kg/m2, and 64% (P=0.0007) and 41% (P=0.008) higher, respectively, than women with BMI < 20 kg/m2. Relative to men and women with BMI < 22.5 kg/m2, the odds for developing diabetes during follow-up increased by 119% (P=0.009) and 116% (P=0.17), respectively, for those with 22.5 < or = BMI < 25 kg/m2.

CONCLUSIONS

Greater BMI and larger waist circumference increase the risks for hypertension, high cholesterol, and diabetes even among normal-weight nonsmoking runners, although overall risks remain relatively low vis-a-vis those for the overweight or obese.

Maintaining vigorous activity attenuates 7-yr weight gain in 8340 runners

INTRODUCTION/PURPOSE

Body weight generally increases with aging in Western societies. Although training studies show that exercise produces acute weight loss, it is unclear whether the long-term maintenance of vigorous exercise attenuates the trajectory of age-related weight gain. Specifically, prior studies have not tested whether the maintenance of physical activity, in the absence of any change in activity, prevents weight gain.

METHODS

Prospective study of 6119 male and 2221 female runners whose running distances changed < 5 km x wk(-1) between baseline and follow-up surveys 7 yr later.

RESULTS

On average, men who maintained modest (0-23 km x wk(-1)), intermediate (24-47 km x wk(-1)), or prolonged running distances (> or = 48 km x wk(-1)) all gained weight through age 64; however, those who maintained > or = 48 km x wk(-1) had one half the average annual weight gain of those who maintained < 24 km x wk(-1). For example, between the ages of 35 and 44 in men and 30 and 39 yr in women, those who maintained < 24 km x wk(-1) gained, on average, 2.1 and 2.9 kg more per decade than those averaging > 48 km x wk(-1). Age-related weight gain, and its attenuation by maintained exercise, were both greater in younger than in older men. Men's gains in waist circumference with age, and its attenuation by maintaining running, were the same in older and younger men. Regardless of age, women increased their body weight, waist circumference, and hip circumference over time, and these measurements were attenuated in proportion to their maintained running distance. In both sexes, running disproportionately prevented more extreme increases in weight.

CONCLUSION

As they aged, men and women gained less weight in proportion to their levels of sustained vigorous activity. This long-term beneficial effect is in addition to the acute weight loss that occurs with increased activity.

Obesity and eye diseases

The prevalence of obesity has reached epidemic proportions in many countries. Although its impact on overall health is well documented, less is known about the ocular manifestations of obesity. Among different eye diseases, obesity has been linked with age-related cataract, glaucoma, age-related maculopathy, and diabetic retinopathy. Numerous population-based and prospective studies support an association between obesity and risk of age-related cataract. However, the nature and strength of these associations, particularly with the different cataract subtypes, remains to be determined. There is strong evidence that obesity is associated with elevated intraocular pressure, but there is no convincing data to support a more direct association between obesity and glaucomatous optic neuropathy. Studies to date have not found a consistent pattern of association between obesity and risk of age-related maculopathy or diabetic retinopathy. Thus, although obesity may be a risk factor for many ocular conditions, the present literature is inadequate to establish any convincing associations. Furthermore, whether weight loss reduces the risk of eye diseases remains unresolved. Because of the potential public health impact of obesity, there is a greater need to understand its ocular effects.

Endurance exercise training raises high-density lipoprotein cholesterol and lowers small low-density lipoprotein and very low-density lipoprotein independent of body fat phenotypes in older men and women

Endurance exercise training improves plasma lipoprotein and lipid profiles and reduces cardiovascular disease risk. However, the effect of endurance exercise training, independent of diet and body fat phenotypes, on plasma lipoprotein subfraction particle concentration, size, and composition as measured by nuclear magnetic resonance (NMR) spectroscopy is not known. We hypothesized that 24 weeks of endurance exercise training would independently improve plasma lipoprotein and lipid profiles as assessed by both conventional and novel NMR measurement techniques. One hundred sedentary, healthy 50- to 75-year-olds following a standardized diet were studied before and after 24 weeks of aerobic exercise training. Lipoprotein and lipid analyses, using both conventional and NMR measures, were performed at baseline and after 24 weeks of exercise training. Relative and absolute maximum oxygen consumption increased 15% with exercise training. Most lipoprotein and lipid measures improved with 24 weeks of endurance exercise training, and these changes were consistently independent of baseline body fat and body fat changes with training. For example, with exercise training, total cholesterol, triglycerides, and low-density lipoprotein cholesterol (LDL-C) decreased significantly (2.1+/-1.8 mg/dL, P=.001; -17+/-3.5 mg/dL, P<.0001; and -0.7+/-1.7 mg/dL, P<.0001, respectively), and high-density lipoprotein cholesterol subfractions (HDL3-C and HDL2-C) increased significantly (1.9+/-0.5 mg/dL, P=.01, and 1.2+/-0.3 mg/dL, P=.02, respectively). Particle concentrations decreased significantly for large and small very low-density lipoprotein particles (-0.7+/-0.4 nmol/L, P<.0001, and -1.1+/-1.7 nmol/L, P<.0001, respectively), total, medium, and very small LDL particles (-100+/-26 nmol/L, P=.01; -26+/-7.0 nmol/L, P=.004; and -103+/-27 nmol/L, P=.02, respectively), and small HDL particles (-0.03+/-0.4 micromol/L, P=.007). Mean very low-density lipoprotein particle size also decreased significantly (-1.7+/-0.9 nm, P<.0001) and mean HDL particle size increased significantly with exercise training (0.1+/-0.0 nm, P=.04). These results show that 24 weeks of endurance exercise training induced favorable changes in plasma lipoprotein and lipid profiles independent of diet and baseline or change in body fat.

Physical Activity and Weight Management Across the Lifespan

This review discusses key findings and recommendations related to the role of physical activity in weight gain prevention, weight loss, and weight-loss maintenance across the lifespan. For weight gain prevention, epidemiological and clinical studies suggest that regular physical activity is critical, with increases above the recommended 30 min daily for health (e.g., to 45 to 60 min daily) potentially desirable for curtailing weight gain. For weight loss, clinical studies suggest that physical activity interventions alone usually produce only modest results. Combining physical activity with dietary interventions increases the chance of success, especially at higher levels of physical activity (e.g., 200 to 300 min or more weekly). For weight-loss maintenance, high levels of physical activity (e.g., 40 to 90 min daily) may be necessary. To manage weight across the lifespan, a comprehensive approach to physical activity is needed supported by public policy interventions that help make physical activity a part of daily life.

Dose-dependent effects of training and detraining on weight in 6406 runners during 7.4 years

OBJECTIVE

Prior randomized and non-randomized training studies have failed to establish a dose-response relationship between vigorous exercise and weight loss; this failure may be due, in part, to their short durations and small sample sizes. The objectives of this study were to determine whether exercise reduces body weight and to examine the dose-response relationships between changes in exercise and changes in total and regional adiposity.

RESEARCH METHODS AND PROCEDURES

This was a large prospective study of 3973 men and 1444 women who quit running (detraining), 270 men and 146 women who started running (training), and 420 men and 153 women who remained sedentary during 7.4 years of follow-up. The outcomes measured were weekly running distance, body weight, BMI, body circumferences, and bra cup size.

RESULTS

There were significant inverse relationships between the changes in the amount of vigorous exercise (km/wk run) and the changes in weight and BMI in men (slope +/- standard error: -0.039 +/- 0.005 kg/km per week and -0.012 +/- 0.002 kg/m(2) per km/wk, respectively) and in older women (-0.060 +/- 0.018 kg/km per week and -0.022 +/- 0.007 kg/m(2) per km/wk) who quit running, and in initially sedentary men (-0.098 +/- 0.017 kg/km per week and -0.032 +/- 0.005 kg/m(2) per km/wk) and women (-0.062 +/- 0.023 kg/km per week and -0.021 +/- 0.008 kg/m(2) per km/wk) who started running. Changes in waist circumference, an indicator of intra-abdominal fat, were also inversely related to changes in running distance in men who quit (-0.026 +/- 0.005 cm/km per week) or started running (-0.078 +/- 0.017 cm/km per week).

DISCUSSION

The initiation of vigorous exercise and its cessation decrease and increase, respectively, body weight and intra-abdominal fat, and these changes are proportional to the change in exercise dose.

Exercise for overweight or obesity

BACKGROUND

Clinical trials have shown that exercise in adults with overweight or obesity can reduce bodyweight. There has been no quantitative systematic review of this in The Cochrane Library.

OBJECTIVES

To assess exercise as a means of achieving weight loss in people with overweight or obesity, using randomised controlled clinical trials.

SEARCH STRATEGY

Studies were obtained from computerised searches of multiple electronic bibliographic databases. The last search was conducted in January 2006.

SELECTION CRITERIA

Studies were included if they were randomised controlled trials that examined body weight change using one or more physical activity intervention in adults with overweight or obesity at baseline and loss to follow-up of participants of less than 15%.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data.

MAIN RESULTS

The 43 studies included 3476 participants. Although significant heterogeneity in some of the main effects' analyses limited ability to pool effect sizes across some studies, a number of pooled effect sizes were calculated. When compared with no treatment, exercise resulted in small weight losses across studies. Exercise combined with diet resulted in a greater weight reduction than diet alone (WMD -1.1 kg; 95% confidence interval (CI) -1.5 to -0.6). Increasing exercise intensity increased the magnitude of weight loss (WMD -1.5 kg; 95% CI -2.3 to -0.7). There were significant differences in other outcome measures such as serum lipids, blood pressure and fasting plasma glucose. Exercise as a sole weight loss intervention resulted in significant reductions in diastolic blood pressure (WMD -2 mmHg; 95% CI -4 to -1), triglycerides (WMD -0.2 mmol/L; 95% CI -0.3 to -0.1) and fasting glucose (WMD -0.2 mmol/L; 95% CI -0.3 to -0.1). Higher intensity exercise resulted in greater reduction in fasting serum glucose than lower intensity exercise (WMD -0.3 mmol/L; 95% CI -0.5 to -0.2). No data were identified on adverse events, quality of life, morbidity, costs or on mortality.

AUTHORS' CONCLUSIONS

The results of this review support the use of exercise as a weight loss intervention, particularly when combined with dietary change. Exercise is associated with improved cardiovascular disease risk factors even if no weight is lost.

Bariatric surgery for morbid obesity: risks and benefits in chronic kidney disease patients

Obesity is one of the most preventable causes of morbidity and mortality of the 21st century. Chronic kidney disease (CKD) has been a largely overlooked consequence of obesity; however, accumulating evidence elucidates the association. Obesity is at the core, promoting a cascade of secondary pathologies including diabetes, dyslipidemia, inflammation, hypertension, and the metabolic syndrome; these comorbidities constitute great risk for CKD. With the diagnosis of CKD, there is an increased threat of cardiovascular disease and the attendant increase in morbidity and mortality rates. Substantial weight loss in the obese population can be effectively achieved and maintained through bariatric surgery, which confers major health benefits by producing resolution or improvement of obesity-related comorbidities. This surgical procedure presents an early hazard of acute on chronic kidney failure, which is offset by a potential improvement in the risk of CKD progression with anticipated improvement in hypertension, diabetes, and CKD risk factors. Future research is needed to describe the clinical course and risks and benefits of bariatric surgery in the CKD population.

Evidence for prescribing exercise as therapy in chronic disease

Considerable knowledge has accumulated in recent decades concerning the significance of physical activity in the treatment of a number of diseases, including diseases that do not primarily manifest as disorders of the locomotive apparatus. In this review we present the evidence for prescribing exercise therapy in the treatment of metabolic syndrome-related disorders (insulin resistance, type 2 diabetes, dyslipidemia, hypertension, obesity), heart and pulmonary diseases (chronic obstructive pulmonary disease, coronary heart disease, chronic heart failure, intermittent claudication), muscle, bone and joint diseases (osteoarthritis, rheumatoid arthritis, osteoporosis, fibromyalgia, chronic fatigue syndrome) and cancer, depression, asthma and type 1 diabetes. For each disease, we review the effect of exercise therapy on disease pathogenesis, on symptoms specific to the diagnosis, on physical fitness or strength and on quality of life. The possible mechanisms of action are briefly examined and the principles for prescribing exercise therapy are discussed, focusing on the type and amount of exercise and possible contraindications.

Aerobic exercise and HDL2-C: a meta-analysis of randomized controlled trials

PURPOSE

Use the meta-analytic approach to examine the effects of aerobic exercise on high-density lipoprotein two cholesterol (HDL2-C) in adults. STUDY SOURCES: (1) Computerized literature searches; (2) cross-referencing from retrieved articles; (3) hand-searching; and (4) expert review of our reference list.

STUDY SELECTION

(1) Randomized controlled trials; (2) aerobic exercise > or = 8 weeks; (3) adults > or = 18 years of age; (4) studies published in journal, dissertation, or master's thesis format; (5) studies published in the English-language between January 1, 1955 and January 1, 2003; and (6) assessment of HDL2-C in the fasting state.

DATA ABSTRACTION

All coding conducted by both authors, independent of each other. Discrepancies were resolved by consensus.

RESULTS

Nineteen randomized controlled trials representing 20 HDL2-C outcomes from 984 males and females (516 exercise, 468 control) were pooled for analysis. Using random-effects modeling and bootstrap confidence intervals (BCI), a statistically significant increase of approximately 11% was observed for HDL2-C (X +/- S.E.M., 2.6 +/- 0.9 mg/dl, 95% BCI, 1.0-4.4 mg/dl). With each study deleted from the model once, results remained statistically significant. Increases in HDL2-C were independent of decreases in body weight, body mass index (kg/m2), and percent body fat.

CONCLUSION

Aerobic exercise increases HDL2-C in adults.

Effectiveness of altering serum cholesterol levels without drugs

Drug therapy with statins and other agents can result in dramatic lipid-lowering effects. Despite the wealth of data supporting the beneficial effects of pharmacologic therapy on cardiovascular risk, patients often express a desire to accomplish similar goals with diet alone. And, except for patients with extreme cholesterol elevations, consensus panels all promote dietary therapy as an initial step in the treatment of hyperlipidemia. This review examines a variety of dietary strategies designed to lower lipid levels, including the American Heart Association diet, the Ornish diet, the Mediterranean diet, exercise, phytosterols, fiber, soy products, and fish oil. Though the declines in low-density lipoprotein cholesterol levels with these methods range from 0% to 37%, cardiovascular risk may be more significantly impacted than would be predicted from these changes alone. Significant benefits can be reaped from nonpharmacologic measures.

Aerobic exercise and lipids and lipoproteins in men: a meta-analysis of randomized controlled trials

BACKGROUND: Aerobic exercise is recommended for improving lipoprotein and lipid levels which at less than their optimal levels are risk factors for cardiovascular disease. Evidence seems lacking for the effectiveness of exercise in reducing these levels, possibly due to small sizes in studies. We concluded a meta-analysis of the studies to examine the effects of aerobic exercise on lipids and lipoproteins in adult men. METHODS: Studies were retrieved via computerized literature searches, cross-referencing from retrieved articles, hand-searching, and expert review of our reference list. Inclusion criteria were randomized controlled trials, aerobic exercise ≥8 weeks, adult men ≥18 years of age, studies published in journal, dissertation, or master's thesis format, studies published in the English-language between January 1, 1955 and January 1, 2003, and assessment of one or more of the following lipids and lipoproteins: total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDLC), and triglycerides (TG). All coding was conducted by both authors, independent of each other. Discrepancies were resolved by consensus. RESULTS: Forty-nine randomized controlled trials representing up to 67 outcomes from 2,990 men (1,741 exercise, 1,249 control) were pooled for analysis. Using random-effects modeling, statistically significant improvements were observed for TC, HDL-C and TG, and a trend for decreases was observed for LDL-C. Changes were equivalent to improvements of 2% for TC and HDL-C, 3% of LDL-C, and 9% for TG. CONCLUSIONS: Aerobic exercise reduces TC and TG and increases HDL-C in men 18 years of age and older.

Cross-sectional relationships of exercise and age to adiposity in 60,617 male runners

INTRODUCTION/PURPOSE

To assess in men whether exercise affects the estimated age-related increase in adiposity, and contrariwise, whether age affects the estimated exercise-related decrease in adiposity.

METHODS

Cross-sectional analyses of 64,911 male runners who provided data on their body mass index (97.6%) and waist circumference (91.1%).

RESULTS

Between 18 and 55 yr old, the decline in BMI with weekly distance run (slope +/- SE) was significantly greater in men 25-55 yr old than in younger men (slope +/- SE: -0.036 +/- 0.001 vs -0.020 +/- 0.002 kg x m(-2) per km x wk(-1)). Declines in waist circumference with distance were also significantly greater in older than younger men (P < 10(-9)), that is, the slopes decreased progressively from -0.035 +/- 0.004 cm per km x wk(-1) in 18- to 25-yr-old men to -0.097 +/- 0.003 cm per km x wk(-1) in 50- to 55-yr-old men). Increases in BMI with age were greater for men who ran under 16 km.wk(-1) than for relatively longer distance runners. Waist circumference increased with age at all running distances, but the increase diminished by running further (0.259 +/- 0.015 cm x yr(-1) if running <8 km x wk(-1) and 0.154 +/- 0.003 cm x yr(-1) for >16 km x wk(-1)). In men 50-85 yr old, BMI declined -0.038 +/- 0.001 kg x m(-2) per km x wk(-1) run when adjusted for age and declined -0.054 +/- 0.003 kg x m(-2) (increased 0.021 +/- 0.007 cm) per year of age when adjusted for running distance. Their waist circumference declined -0.096 +/- 0.002 cm per km x wk(-1) run when adjusted for age and increased 0.021 +/- 0.007 cm per year of age when adjusted for running distance.

CONCLUSIONS

These data suggest that age and vigorous exercise interact with each other in affecting men's adiposity and are consistent with the proposition that vigorous physical activity must increase with age to prevent middle-age weight gain.

Nonsurgical and surgical treatment of obesity

An increasing number of morbidly obese patients are presenting for surgery, with the potential for increased perioperative morbidity and mortality. This article reviews surgical and nonsurgical options in the management of morbidly obese patients. Overweight and obese individuals should be treated with diet, exercise, and behavioral therapy. The failure of this approach is an indication for pharmacologic therapy. Bariatric surgery reduces obesity-related complications and reduces long-term morbidity, mortality, and health care resources use.

Aerobic exercise, lipids and lipoproteins in overweight and obese adults: a meta-analysis of randomized controlled trials

OBJECTIVE

Use the meta-analytic approach to examine the effects of aerobic exercise on lipids and lipoproteins in overweight and obese adults.

DATA SOURCES

(1) Computerized literature searches, (2) cross-referencing from review and original articles, (3) hand searching, and (4) expert review of reference list.

STUDY SELECTION

(1) randomized controlled trials, (2) aerobic exercise > or =8 weeks, (3) adult humans > or =18 y of age, (4) all subjects overweight or obese (BMI > or =25 kg/m(2)), (5) studies published in journal, dissertation, or master's thesis format, (6) studies published in the English-language, (7) studies published between 1 January 1955 and 1 January 2003, (8) assessment of one or more of the following lipid and/or lipoprotein variables: total cholesterol (TC), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), and triglycerides (TG).

DATA ABSTRACTION

Dual-coding by the first two authors (inter-rater agreement=0.96).

RESULTS

In total, 13 studies representing 31 groups (17 exercise, 14 control), 613 subjects (348 exercise, 265 control), and up to 17 outcomes were available for pooling. Across all categories, random-effects modeling resulted in statistically significant improvements for TC (X +/- s.e.m., - 3.4+/-1.7 mg/dl, 95% CI, - 6.7 to - 0.2 mg/dl) and TG (X +/-s.e.m., - 16.1+/-7.3 mg/dl, 95% CI, - 30.2 to - 2.1 mg/dl) but not HDL (X +/- s.e.m., 1.6+/-0.8 mg/dl, 95% CI, - 0.02 to 3.2 mg/dl) or LDL (X +/-s.e.m., - 0.5+/-1.3 mg/dl, 95% CI, - 3.0 to 2.0 mg/dl). Changes were equivalent to improvements of 2% (TC), 11% (TG), 3% (HDL), and 0.3% (LDL). After conducting sensitivity analyses (each study deleted from the model once), only decreases in TG remained statistically significant. Increases in HDL were associated with increases in maximum oxygen consumption (VO(2 max) in ml/kg/min, r=0.75, P=0.002) and decreases in body weight (r=0.77, P<0.001), while decreases in LDL were associated with decreases in body weight (r=0.75, P=0.009).

CONCLUSIONS

Aerobic exercise decreases TG in overweight and obese adults. However, a need exists for additional randomized controlled trials in various overweight and/or obese populations above and beyond those included in our analysis.

The comparative and cumulative effects of a dietary restriction and exercise on weight loss

OBJECTIVE

To assess the independence of changes made in diet and physical activity for weight loss; and, to examine the comparative and cumulative effects of these behavioral changes on weight loss outcomes.

DESIGN

The observational study is based on longitudinal data collected from 674 women and 288 men enrolled in a 2-year weight loss program introduced into a managed care setting.

MEASUREMENTS

The outcome variable was body mass index (BMI) change from baseline to 2-year follow-up. Primary independent variables were changes in physical activity and dietary fat intake, assessed as continuous measures using the Paffenbarger Physical Activity Questionnaire and Block Fat Screener Questionnaire, respectively. Two-way ANCOVA was used to assess the relative effect on BMI of behavioral changes.

RESULTS

Study results showed no preference for diet or physical activity change as a weight loss strategy. For both genders, the relationship between the two behaviors was synergistic rather than compensatory. Examination of the comparative benefits of behavioral changes indicated that, for women and men, restricting fat intake was more effective than increasing exercise for weight loss. While fat restrictions alone contributed to weight loss in both genders, exercise alone provided weight loss benefits to men, only. The cumulative effect of weight loss behaviors varied by gender. In women, an interaction was observed. The response of weight to fat restriction was greater among those who increased their exercise moderately or substantially. In men, there was no interaction; exercise increases helped to offset weight gain or provided small weight loss benefits at all levels of dietary fat change.

CONCLUSION

Dietary changes appeared to be more effective than increased physical activity for weight loss. For women, the cumulative effect of concomitant changes in diet and exercise on weight loss was more than additive.

Behavioral Versus Genetic Correlates of Lipoproteins and Adiposity in Identical Twins Discordant for Exercise

Background— Lipoprotein and weight differences between vigorously active and sedentary monozygotic (MZ) twins were used to (1) estimate the effects of training while controlling for genotype and (2) estimate genetic concordance (ie, similarity) in the presence of divergent lifestyles.

Methods and Results— Thirty-five pairs of MZ twins (25 male, 10 female) were recruited nationally who were discordant for vigorous exercise (running distances differed by ≥40 km in male and ≥32 km in female twins). The active twins ran an average (mean±SD) of 63.0±20.4 km/wk, whereas the mostly sedentary twins averaged 7.0±13.5 km/wk. The active twins had significantly lower body mass index (difference±SE, −2.12±0.57 kg/m 2 , P =0.0007) and significantly higher HDL cholesterol (0.14±0.04 mmol/L, P =0.004), HDL 2 (2.71±1.04 U, P =0.01), and apolipoprotein (apo) A-I (0.10±0.03 g/L, P =0.004). Despite the difference in lifestyle, when adjusted for sex, the correlations between the discordant MZ twin pairs were significant ( P <0.01) for HDL cholesterol ( r =0.69), apoA-I ( r =0.58), and HDL 2 ( r =0.67). There was no significant MZ twin correlation for body mass index ( r =0.17). None of the active twins having an overweight twin were themselves overweight.

Conclusions— Behavior (vigorous exercise) may reduce genetic influences on body mass index. In contrast, genetics (or shared environment) substantially influences HDL cholesterol and HDL subclasses, even in the presence of extreme behavioral differences. There may be greater individual control over moderate degrees of obesity, whereas low HDL cholesterol may be largely predetermined and less effectively treated by vigorous exercise.

Physical activity considerations for the treatment and prevention of obesity

Overweight and obesity present significant public health concerns because of the link with numerous chronic health conditions. Excess body weight is a result of an imbalance between energy intake and energy expenditure. Physical activity is the most variable component of energy expenditure and therefore has been the target of behavioral interventions to modify body weight. It appears that physical activity is an important component on long-term weight control, and therefore adequate levels of activity should be prescribed to combat the obesity epidemic. Although there is evidence that 30 min of moderate-intensity physical activity may improve health outcomes, the amount of physical activity that may be necessary to control body weight may be >30 min/d. There is a growing body of scientific literature suggesting that at least 60 min of moderate-intensity physical activity may be necessary to maximize weight loss and prevent significant weight regain. Moreover, adequate levels of physical activity appear to be important for the prevention of weight gain and the development of obesity. Physical activity also appears to have an independent effect on health-related outcomes when compared with body weight, suggesting that adequate levels of activity may counteract the negative influence of body weight on health outcomes. Thus, it is important to target intervention strategies to facilitate the adoption and maintenance of an adequate amount of physical activity to control body weight.

Interleukin-6 genotype is associated with high-density lipoprotein cholesterol responses to exercise training

BACKGROUND

High-density lipoprotein cholesterol (HDL-C) and its subfractions are modifiable with exercise training and these responses are heritable. The interleukin-6 (IL6)-174G/C polymorphism may be associated with HDL-C levels. We hypothesized that the IL6-174G/C polymorphism would be associated with plasma HDL-C response to exercise training.

METHODS AND RESULTS

Sixty-five 50- to 75-year-olds on a standardized diet were studied before and after 24 weeks of aerobic exercise training. Significant differences existed among genotype groups for change with exercise training in HDL-C, HDL3-C, integrated HDL4,5NMR-C, and HDLsize. The CC genotype group increased HDL-C more than the GG (7.0 +/- 1.3 v. 1.0 +/- 1.1 mg/dL, p = 0.001) and GC groups (3.3 +/- 0.9 mg/dL, p = 0.02); for HDL3-C, the CC group increased more than the GG (6.1 +/- 1.0 v. 0.9 +/- 0.9, mg/dL p < 0.001) and GC groups (2.5 +/- 0.7 mg/dL, p = 0.006). Integrated HDL4,5NMR-C increased more in the CC than GG group (6.5 +/- 1.6 mg/dL v. 1.0 +/- 1.3 mg/dL, p = 0.01), as did HDLsize compared to the GG (CC: 0.3 +/- 0.1 v. GG: 0.1 +/- 0.1 nm, p = 0.02) and GC (0.0 +/- 0.0 nm, p = 0.007) groups.

CONCLUSIONS

IL6 genotype is associated with HDL-C response to exercise training.