History of sport participation in relation to obesity and related health behaviors in women

Exploring the relationship between adolescent biological maturation, physical activity, and sedentary behaviour: a systematic review and narrative synthesis

CONTEXT

Across adolescence, there is a notable decline in physical activity in boys and girls. Maturational timing may be a risk factor for disengagement from physical activity and increased sedentary behaviours during adolescence.

OBJECTIVE

This systematic review aimed to summarise literature that examined the relationship between maturational timing, physical activity and sedentary behaviour in adolescents.

METHODS

Six electronic databases were searched for articles that assessed biological maturation and physical activity (including sports participation and active transportation) or sedentary behaviours in adolescents. Two reviewers conducted title, abstract, and full-text screening, reference and forward citation searches. Included articles were evaluated for quality using a standardised tool. A narrative synthesis was used to analyse the findings due to the heterogeneity of the studies.

RESULTS

Searches yielded 78 articles (64 unique studies) that met the inclusion criteria, representing 242,316 participants (153,179 unique). Studies ranged from 30.0% (low) to 91.7% (high) in quality. An inverse relationship between maturational timing and physical activity (in 50 and 60% of studies in boys and girls, respectively) and a positive relationship between maturational timing and sedentary behaviour (in 100% and 53% of studies in boys and girls, respectively) was most commonly reported. Evidence supporting an association between maturational timing, sports participation, and active transportation was inconsistent.

CONCLUSIONS

While this review demonstrates some evidence for early maturational timing as a risk factor for disengagement from physical activity and increase in sedentary behaviours, the reviewed literature also demonstrates that this relationship is complex. Future research that tracks maturity-related variations in physical activity and sedentary behaviours over adolescence is warranted.

Changes in diet, and the relationship between diet and physical activity within and across the lifetime of current ultra-endurance exercisers

BACKGROUND

There is currently no information on the lifetime diet of ultra-endurance exercisers. This study describes changes in diet across the lifetime of current ultra-endurance exercisers and the relationship between diet and physical activity (specifically ultra-endurance exercise [UEE]).

METHODS

Lifetime physical activity and diet were assessed in current ultra-endurance exercisers (N.=120; ages 21-74 years) over six life periods (5-12, 13-18, 19-30, 31-45, 46-60, 61-75 years). Using the life period having the largest absolute increase in UEE (IUEE), diet was assessed according to food category scores and dietary patterns. Changes in lifetime diet were described by comparing food category scores between adjacent life periods. Differences in food category scores were investigated between the life period for each IUEE group and the preceding life period and associations between dietary patterns and UEE were investigated within each IUEE group. Relationships between lifetime diet and UEE were investigated by examining associations between lifetime food category scores and lifetime UEE.

RESULTS

The participant group had significant increases in all food category scores from 13-18 to 19-30 years and significant decreases in all food category scores from 19-30 to 31-45 years. UEE correlated negatively with the Western style dietary pattern in the IUEE19-30 group and positively with the fruit and vegetable dietary pattern in the IUEE31-45 group. There was a positive correlation between lifetime UEE and lifetime vegetables and fruit category scores.

CONCLUSIONS

The ultra-endurance exercisers in this study exhibited changes in diet similar to general populations, which appear to reflect typical nutritional requirements across the lifespan.

The NBA and Youth Basketball: Recommendations for Promoting a Healthy and Positive Experience

Participation in sports offers both short-term and long-term physical and psychosocial benefits for children and adolescents. However, an overemphasis on competitive success in youth sports may limit the benefits of participation, and could increase the risk of injury, burnout, and disengagement from physical activity. The National Basketball Association and USA Basketball recently assembled a group of leading experts to share their applied research and practices to address these issues. This review includes the group's analysis of the existing body of research regarding youth sports participation and the related health, performance, and psychosocial outcomes. Based upon this, age-specific recommendations for basketball participation are provided that aim to promote a healthy and positive experience for youth basketball players.

The Role of Youth Sports in Promoting Children's Physical Activity and Preventing Pediatric Obesity: A Systematic Review

Youth sport participation plays an important role in promoting physical activity among children and may be a possible venue for the prevention of pediatric obesity. To design effective physical activity interventions, it is imperative to understand how different aspects of sport participation influence physical activity (PA). The purpose of this article is to present a comprehensive review of the impact of youth sport participation on children's PA and obesity status. A total of 44 studies published up to January 2014 concerning youth sport participation, PA, and obesity status were identified. Inclusion criteria were studies comparing PA levels of sport participants to nonparticipants or those comparing PA levels in different sport types and settings. Studies with the outcome variables of obesity status (e.g., body mass index, fat percentage, waist circumference) were also included. Participation in youth sport was positively associated with children's PA levels, and youth participating in sports were more likely to persist in their PA. However, the relationship between youth sport participation and obesity status was inconclusive. Educators and sports professionals should find ways to involve children in various sports settings and policies and help obese children engage more in sports.

The Determinants of Physical Activity in Rural Women, Aged 20 to 44 Years, in Georgia

Physical activity rates in rural women are very low. The purpose of this study was to explore the determinants of physical activity in rural women aged 20 to 44 years. A survey was used to collect data on a cluster sample of 184 participants. This study was guided by Self-Determination Theory. Survey data suggest that the highest type of motivation was identified regulation, and husband's support had the strongest effect on physical activity. Findings suggest that a history of sports participation can lead to the formation of intrinsic motivation. The results will assist in developing effective physical activity interventions.

The Contribution of Physical Activity and Media Use during Childhood and Adolescence to Adult Women's Body Image

This study aimed to investigate the effects of both past and current physical activity and media use on women's body image. A sample of 144 female undergraduate students completed measures of current physical activity, media use and body image, as well as providing retrospective reports of their physical activity participation and media usage during childhood and adolescence. Regression analyses showed that childhood experiences of physical activity and media use predicted adult body-image concerns more strongly than current activities. It was concluded that early experiences of both physical activity and media use during childhood and adolescence play an important role in the development of adult women's body image.

Weekly Physical Activity Levels of Older Adults Regularly Using a Fitness Facility

The aim of this paper was to determine if weekly physical activity levels were greater in an independent-living older adult population that was regularly participating in structured fitness activities. Also, lifetime exercise history and sex differences were investigated in an effort to understand how they relate to current weekly step activity. Total weekly step counts, measured with a pedometer, were assessed in two older adult groups; the first consisted of members of a local senior center who regularly used the fitness facility (74.5 ± 6.0 yrs; mean ± SD) while the second group consisted of members who did not use the fitness facility (74.8 ± 6.0 yrs). Participants also completed the Lifetime Physical Activity Questionnaire (LPAQ). No significant difference was found in the total number of weekly steps between groups (p = 0.88) or sexes (p = 0.27). The LPAQ suggested a significant decline in activity with aging (p = 0.01) but no difference between groups (p = 0.54) or sexes (p = 0.80). A relationship was observed between current step activity and MET expenditure over the past year (p = 0.008, r (2) = 0.153) and from ages 35 to 50 years (p = 0.037, r (2) = 0.097). The lack of difference in weekly physical activity level between our groups suggests that independent-living older adults will seek out and perform their desired activity, in either a scheduled exercise program or other leisure-time activities. Also, the best predictor of current physical activity level in independent-living older adults was the activity performed over the past year.

Psychological need satisfaction, intrinsic motivation and affective response to exercise in adolescents

OBJECTIVES

To further understanding of the factors influencing adolescents' motivations for physical activity, the relationship of variables derived from Self-Determination Theory to adolescents' affective response to exercise was examined.

DESIGN

Correlational.

METHOD

Adolescents (N = 182) self-reported psychological needs satisfaction (perceived competence, relatedness, and autonomy) and intrinsic motivation related to exercise. In two clinic visits, adolescents reported their affect before, during, and after a moderate-intensity and a hard-intensity exercise task.

RESULTS

Affective response to exercise and psychological needs satisfaction independently contributed to the prediction of intrinsic motivation in hierarchical linear regression models. The association between affective response to exercise and intrinsic motivation was partially mediated by psychological needs satisfaction.

CONCLUSIONS

Intrinsic motivation for exercise among adolescents may be enhanced when the environment supports perceived competence, relatedness, and autonomy, and when adolescents participate in activities that they find enjoyable.

Influence of sports, physical education, and active commuting to school on adolescent weight status

OBJECTIVE

To compare the associations between weight status and different forms of physical activity among adolescents.

METHODS

We conducted telephone surveys with 1718 New Hampshire and Vermont high school students and their parents as part of a longitudinal study of adolescent health. We surveyed adolescents about their team sports participation, other extracurricular physical activity, active commuting, physical education, recreational activity for fun, screen time, diet quality, and demographics. Overweight/obesity (BMI for age ≥ 85th percentile) and obesity (BMI for age ≥ 95 percentile) were based on self-reported height and weight.

RESULTS

Overall, 29.0% (n = 498) of the sample was overweight/obese and 13.0% (n = 223) were obese. After adjustments, sports team participation was inversely related to overweight/obesity (relative risk [RR] = 0.73 [95% confidence interval (CI): 0.61, 0.87] for >2 sports teams versus 0) and obesity (RR = 0.61 [95% CI: 0.45, 0.81] for >2 sports teams versus 0). Additionally, active commuting to school was inversely related to obesity (RR = 0.67 [95% CI: 0.45, 0.99] for >3.5 days per week versus 0). Attributable risk estimates suggest obesity prevalence would decrease by 26.1% (95% CI: 9.4%, 42.8%) if all adolescents played on 2 sports teams per year and by 22.1% (95% CI: 0.1%, 43.3%) if all adolescents walked/biked to school at least 4 days per week.

CONCLUSIONS

Team sport participation had the strongest and most consistent inverse association with weight status. Active commuting to school may reduce the risk of obesity, but not necessarily overweight, and should be studied further. Obesity prevention programs should consider strategies to increase team sport participation among all students.

The influence of a behavior modification interventional program on body mass index in obese adolescents

BACKGROUND/PURPOSE

The prevalence of obesity and overweight among children and adolescents is increasing rapidly. The present research was performed to determine the influence of a ''behavior modification'' program on body mass index (BMI) in obese public high school students in Iran.

METHODS

In this study, 152 adolescence and their parents were selected from 12 high schools of Khorram Abad from 2004 to 2006, and they were randomly assigned to either the intervention or the control groups. The "behavior modification" interventional program consisted of nutritional education, modifying dietary habits, teaching exercise programs, teaching nutritional facts to the parents, and performing exercises 3 days a week. The height and weight as well as waist, hip, and wrist circumferences of the participants were measured before and after implementing the interventional program. BMI and waist to hip ratio (WHR) were calculated. The adolescents and parents completed a nutrition knowledge questionnaire. Adolescents also completed the Beck's Depression Questionnaire.

RESULTS

Adolescent's mean weight, BMI, and waist and hip circumferences decreased significantly after implementing the interventional program, in the intervention group (p≤0.001). In addition, the students' and parents' nutrition knowledge increased in the intervention group after implementing the interventional program (p<0.046). The symptoms of depression decreased and the frequency of students without symptoms of depression increased in the case group, but it did not reveal a statistically significant difference between case and control groups.

CONCLUSION

The ''behavior modification'' interventional program is effective in reducing BMI in obese students, and therefore, school principals and planners can play an important role in controlling obesity by implementing this program via the students, their parents, and the school staff.

Do youth sports prevent pediatric obesity? A systematic review and commentary

Sport is a promising setting for obesity prevention among youth, but little is known about whether it prevents obesity. We reviewed research comparing sport participants with nonparticipants on weight status, physical activity, and diet. Among 19 studies, we found no clear pattern of association between body weight and sport participation. Among 17 studies, we found that sport participants are more physically active than those who do not participate. We found seven studies that compared the diet of sport participants with non-participants. These studies reported that youth involved in sport were more likely to consume fruits, vegetables, and milk, and also more likely to eat fast food and drink sugar-sweetened beverages and consume more calories overall. It is unclear from these results whether sports programs, as currently offered, protect youth from becoming overweight or obese. Additional research may foster understanding about how sport, and youth sport settings, can help promote energy balance and healthy body weight.

Governmental interventions and youth physical activity in France

Data from a representative sample of 2474 French youth show that, despite a 7-year French Ministry of Health strategy for nutrition and physical activities, adolescents' motivation to practise sports and physical activities decreased significantly between 2001 and 2008. While this paper focuses on the context of physical activity in France, the general discussion may be applicable to other countries concerned with the obesity pandemic.

Regional brain activation and affective response to physical activity among healthy adolescents

Research has shown that frontal brain activation, assessed via electroencephalographic (EEG) asymmetry, predicts the post-exercise affective response to exercise among adults. Building on this evidence, the present study investigates the utility of resting cortical asymmetry for explaining variance in the affective response both during and after exercise at two different intensities among healthy adolescents. Resting EEG was obtained from 98 adolescents (55% male), who also completed two 30-min exercise tasks on a cycle ergometer at a moderate and hard intensity. Affect (as measured by the Feeling Scale) was assessed prior to exercise, every 10min during exercise, immediately post-exercise, and 10min post-exercise. When moderate exercise was performed first, resting frontal cortical asymmetry was related to the affective response to moderate exercise, such that left-dominant adolescents reported more positive affect compared to right-dominant adolescents. When hard exercise was performed first, the association was not significant. The results are interpreted in light of current theory related to affect in response to exercise.

Personality, physical fitness, and affective response to exercise among adolescents

PURPOSE

Evidence shows that aspects of personality are associated with participation in physical activity. We hypothesized that, among adolescents, behavioral activation (BAS) and behavioral inhibition (BIS) systems would be associated with physical fitness (cardiovascular fitness and percent body fat), enjoyment of exercise, tolerance of and persistence in high-intensity exercise, and affective response to an acute exercise bout.

METHODS

One hundred and forty-six healthy adolescents completed a cardiovascular fitness test, percent body fat assessment (dual-energy x-ray absorptiometer), and two 30-min cycle ergometer exercise tasks at moderate and hard intensities. Questionnaires evaluated BIS/BAS, enjoyment of exercise, and preference and tolerance for high-intensity activity. Affect in response to exercise was assessed using the Feeling Scale (FS) and the Activation Deactivation Adjective Check List (AD ACL).

RESULTS

BIS was negatively correlated with cardiovascular fitness and tolerance for high-intensity exercise, and adolescents with high BIS scores reported more negative FS in response to exercise at both moderate and hard intensities. BAS was positively correlated with enjoyment of exercise, and adolescents with high BAS scores reported having more positive FS and higher energetic arousal on the AD ACL in response to moderate-intensity exercise. The association between BAS and affect was attenuated for the hard-intensity exercise task.

CONCLUSION

These findings suggest that both the drive to avoid punishing stimuli (BIS) and the drive to approach rewarding stimuli (BAS) are related to the affective response to exercise. The BIS may be more strongly associated with fitness-related exercise behavior among adolescents than the BAS, whereas the BAS may play a relatively greater role in terms of subjective exercise enjoyment.

Past-year sports participation, current physical activity, and fitness in urban adolescent girls

BACKGROUND

This study examined associations between sports participation, physical activity, fitness level, and body mass index in ninth-grade girls.

METHODS

Data were analyzed for 221 participants who completed sports participation and physical activity recall questionnaires, an aerobic step test, and height and weight measurement.

RESULTS

On average, participants had low physical activity levels, and many were overweight or obese (47%). About half participated in at least one organized sport in the previous year. Sports participants had higher current estimated energy expenditure compared with non-sports participants (P=.0007). Those who participated on at least two teams were more likely to complete the three-stage step test without reaching their target heart rate than those who did not participate on any teams (P<.03). Past sports participation was positively associated with current physical activity and fitness levels.

CONCLUSION

Urban adolescent girls who participate in sports have increased energy expenditure and higher fitness levels, indicating sports as a potential strategy to improve physical activity and health in this population.

A prospective study of age-specific physical activity and premenopausal breast cancer

BACKGROUND

Physical activity has been consistently associated with lower risk of postmenopausal breast cancer, but its relationship with premenopausal breast cancer is unclear. We investigated whether physical activity is associated with reduced incidence of premenopausal breast cancer, and, if so, what age period and intensity of activity are critical.

METHODS

A total of 64,777 premenopausal women in the Nurses' Health Study II reported, starting on the 1997 questionnaire, their leisure-time physical activity from age 12 to current age. Cox regression models were used to examine the relationship between physical activity, categorized by age period (adolescence, adulthood, and lifetime) and intensity (strenuous, moderate, walking, and total), and risk of invasive premenopausal breast cancer.

RESULTS

During 6 years of follow-up, 550 premenopausal women developed breast cancer. The strongest associations were for total leisure-time activity during participants' lifetimes rather than for any one intensity or age period. Active women engaging in 39 or more metabolic equivalent hours per week (MET-h/wk) of total activity on average during their lifetime had a 23% lower risk of premenopausal breast cancer (relative risk = 0.77; 95% confidence interval = 0.64 to 0.93) than women reporting less activity. This level of total activity is equivalent to 3.25 h/wk of running or 13 h/wk of walking. The age-adjusted incidence rates of breast cancer for the highest (> or = 54 MET-h/wk) and lowest (< 21 MET-h/wk) total lifetime physical activity categories were 136 and 194 per 100 000 person-years, respectively. High levels of physical activity during ages 12-22 years contributed most strongly to the association.

CONCLUSIONS

Leisure-time physical activity was associated with a reduced risk for premenopausal breast cancer in this cohort. Premenopausal women regularly engaging in high amounts of physical activity during both adolescence and adulthood may derive the most benefit.

Participation in physical activity among normal- and overweight Hispanic and non-Hispanic white adolescents

BACKGROUND

The purpose of this study was to determine the relation between weight status and participation in physical activity (PA) among Hispanic and non-Hispanic white (NHW) adolescent boys and girls.

METHODS

In this cross-sectional study, height and weight were measured and a modified 2001 Youth Risk Behavior Survey was administered to 1,302 Hispanic and NHW adolescents, aged 14-17 years, attending high school in Nueces County, Texas. Linear regression analysis was used to assess the relation between weight status (normal weight or "at risk for overweight and overweight" [AR&O]) and PA, including moderate PA, vigorous PA, strength training, participation in team sports, and TV viewing, according to gender and ethnicity.

RESULTS

Thirty-eight percent of adolescents were AR&O, including 32% and 48% of Hispanic girls and boys, respectively, and 22% and 35% of NHW girls and boys, respectively. As expected, boys reported participating in more PAs than girls. Compared with NHW girls, both normal weight and AR&O Hispanic girls reported significantly fewer bouts of moderate activity, less involvement in team sports, and more time watching TV. Normal weight boys reported participating in significantly more vigorous activity than those who were AR&O. Hispanic boys reported more strength training than NHWs; however, they watched significantly more hours of TV than NHW boys.

CONCLUSIONS

Hispanic and NHW high school students reported participation in different PAs; this information may be useful for planning health and physical education curriculum.

Socioeconomic position in childhood and adulthood and weight gain over 34 years: the Alameda County Study

PURPOSE

Socioeconomic position (SEP) has been shown to be related to obesity and weight gain, especially among women. It is unclear how different measures of socioeconomic position may impact weight gain over long periods of time, and whether the effect of different measures vary by gender and age group. We examined the effect of childhood socioeconomic position, education, occupation, and log household income on a measure of weight gain using individual growth mixed regression models and Alameda County Study data collected over thirty four years(1965-1999).

METHODS

Analyses were performed in four groups stratified by gender and age at baseline: women, 17-30 years (n = 945) and 31-40 years (n = 712); men, 17-30 years (n = 766) and 31-40 years (n = 608).

RESULTS

Low childhood SEP was associated with increased weight gain among women 17-30 (0.13 kg/year, p < 0.001). Low educational status was associated with increased weight gain among women 17-30 (0.14 kg/year, p = 0.030), 31-40 (0.14 kg/year, p = 0.014), and men 17-30 (0.20 kg/year, p = 0.001).

CONCLUSION

Log household income was inversely associated with weight gain among men 31-40 (-0.10 kg/yr, p = 0.16). Long-term weight gain in adulthood is associated with childhood SEP and education in women and education and income in men.

Adolescent physical activity and health: a systematic review

Physical activity in adolescence may contribute to the development of healthy adult lifestyles, helping reduce chronic disease incidence. However, definition of the optimal amount of physical activity in adolescence requires addressing a number of scientific challenges. This article reviews the evidence on short- and long-term health effects of adolescent physical activity. Systematic reviews of the literature were undertaken using a reference period between 2000 and 2004, based primarily on the MEDLINE/PubMed database. Relevant studies were identified by examination of titles, abstracts and full papers, according to inclusion criteria defined a priori. A conceptual framework is proposed to outline how adolescent physical activity may contribute to adult health, including the following pathways: (i) pathway A--tracking of physical activity from adolescence to adulthood; (ii) pathway B--direct influence of adolescent physical activity on adult morbidity; (iii) pathway C--role of physical activity in treating adolescent morbidity; and (iv) pathway D - short-term benefits of physical activity in adolescence on health. The literature reviews showed consistent evidence supporting pathway 'A', although the magnitude of the association appears to be moderate. Thus, there is an indirect effect on all health benefits resulting from adult physical activity. Regarding pathway 'B', adolescent physical activity seems to provide long-term benefits on bone health, breast cancer and sedentary behaviours. In terms of pathway 'C', water physical activities in adolescence are effective in the treatment of asthma, and exercise is recommended in the treatment of cystic fibrosis. Self-esteem is also positively affected by adolescent physical activity. Regarding pathway 'D', adolescent physical activity provides short-term benefits; the strongest evidence refers to bone and mental health. Appreciation of different mechanisms through which adolescent physical activity may influence adult health is essential for drawing recommendations; however, the amount of exercise needed for achieving different benefits may vary. Physical activity promotion must start in early life; although the 'how much' remains unknown and needs further research, the lifelong benefits of adolescent physical activity on adult health are unequivocal.

Tracking of physical activity from adolescence to adulthood: a population-based study

OBJECTIVE: To assess the association between regular physical activity in adolescence and leisure-time physical activity in adulthood, with emphasis on gender differences. METHODS: A population-based cross-sectional study was carried out in Pelotas, Southern Brazil, in 2003. A representative sample of households was selected in multiple stages and subjects aged 20-59 years were interviewed. Leisure-time physical activity was evaluated using the International Physical Activity Questionnaire. Data on adolescent physical activity were based on subjects' recall. RESULTS: Of 2,577 subjects interviewed, 27.5% were classified as adequately active, and 54.9% reported regular physical activity in adolescence. Subjects who engaged in regular physical activity during adolescence were more likely to be adequately active in adulthood (adjusted prevalence ratio 1.42; 95% CI: 1.23; 1.65). This effect was stronger in women (adjusted prevalence ratio: 1.51; 95% CI: 1.22; 1.86) than men (adjusted prevalence ratio: 1.35; 95% CI: 1.10; 1.67). CONCLUSIONS: Promoting physical activity in school age may be a successful intervention against the epidemic of adult inactivity. Although women were less likely to report regular physical activity in adolescence, the effect of this experience on adult behavior was stronger than in men.

Opportunities and challenges in the prevention and control of cancer and other chronic diseases: children's diet and nutrition and weight and physical activity

OBJECTIVE

The purpose of this article is to review the role of behavioral research in disease prevention and control, with a particular emphasis on lifestyle- and behavior-related cancer and chronic disease risk factors--specifically, relationships among diet and nutrition and weight and physical activity with adult cancer, and tracking developmental origins of these health-promoting and health-compromising behaviors from childhood into adulthood.

METHOD

After reviewing the background of the field of cancer prevention and control and establishing plausibility for the role of child health behavior in adult cancer risk, studies selected from the pediatric published literature are reviewed. Articles were retrieved, selected, and summarized to illustrate that results from separate but related fields of study are combinable to yield insights into the prevention and control of cancer and other chronic diseases in adulthood through the conduct of nonintervention and intervention research with children in clinical, public health, and other contexts.

RESULTS

As illustrated by the evidence presented in this review, there are numerous reasons (biological, psychological, and social), opportunities (school and community, health care, and family settings), and approaches (nonintervention and intervention) to understand and impact behavior change in children's diet and nutrition and weight and physical activity.

CONCLUSIONS

Further development and evaluation of behavioral science intervention protocols conducted with children are necessary to understand the efficacy of these approaches and their public health impact on proximal and distal cancer, cancer-related, and chronic disease outcomes before diffusion. It is clear that more attention should be paid to early life and early developmental phases in cancer prevention.

Early determinants of physical activity in adolescence: prospective birth cohort study

OBJECTIVE

To examine the effects of early social, anthropometric, and behavioural variables on physical activity in adolescence.

DESIGN

Prospective birth cohort study.

SETTING

Pelotas, southern Brazil.

PARTICIPANTS

4453 adolescents aged 10-12 years participating in the Pelotas 1993 birth cohort study (follow-up rate 87.5%).

MAIN OUTCOME MEASURES

Sedentary lifestyle (< 300 minutes of physical activity per week) and median physical activity score (minutes per week).

RESULTS

The prevalence of a sedentary lifestyle at age 10-12 years was 58.2% (95% confidence interval 56.7% to 59.7%). Risk factors for a sedentary lifestyle in adolescence were female sex, high family income at birth, high maternal education at birth, and low birth order. Weight gain variables at ages 0-1, 1-4, and 4-11 years and overweight at age 1 or 4 years were not significant predictors of physical activity. Levels of physical activity at age 4 years, based on maternal report, were inversely related to a sedentary lifestyle at age 10-12 years.

CONCLUSIONS

Physical activity in adolescence does not seem to be programmed by physiological factors in infancy. A positive association between birth order and activity may be due to greater intensity of play in childhood and adolescence. Tracking of physical activity from age 4 to 10-12 years, however, suggests that genetic factors or early habit formation may be important.

Lifetime Recreational Exercise Activity and Breast Cancer Risk Among Black Women and White Women

BACKGROUND

Physical inactivity is a potentially modifiable breast cancer risk factor. Because few data on this relationship exist for black women, we examined the relationship between breast cancer risk and lifetime and time- or age-specific measures of recreational exercise activity among white women and among black women.

METHODS

The Women's Contraceptive and Reproductive Experiences Study was a multicenter population-based case-control study of black women and white women aged 35-64 years with newly diagnosed invasive breast cancer. We collected detailed histories of lifetime recreational exercise activity during in-person interviews with 4538 case patients with breast cancer (1605 black and 2933 white) and 4649 control subjects (1646 black and 3033 white). Control subjects were frequency-matched to case patients on age, race, and study site. We examined associations between exercise activity measures (metabolic equivalents of energy expenditure [MET]-hours per week per year) and breast cancer risk overall and among subgroups defined by race, other breast cancer risk factors, and tumor characteristics by use of unconditional logistic regression. All statistical tests were two-sided.

RESULTS

Among all women, decreased breast cancer risk was associated with increased levels of lifetime exercise activity (e.g., average MET-hours per week per year, P(trend) = .002). An average annual lifetime exercise activity that was greater than the median level for active control subjects was associated with an approximately 20% lower risk of breast cancer, compared with that for inactivity (for 6.7-15.1 MET-hours/week/year, odds ratio [OR] = 0.82, 95% confidence interval [CI] = 0.71 to 0.93; for > or =15.2 MET-hours/week/year, OR = 0.80, 95% CI = 0.70 to 0.92). The inverse associations did not differ between black and white women (for MET-hours/week/year, P(trend) = .003 and P(trend) = .09, respectively; homogeneity of trends P = .16). No modification of risk was observed by disease stage, estrogen receptor status, or any breast cancer risk factor other than first-degree family history of breast cancer.

CONCLUSIONS

This study supports an inverse association between physical activity and breast cancer among black women and among white women.

TRP64ARG polymorphism of the beta 3-adrenergic receptor gene and obesity risk: effect modification by a sedentary lifestyle

AIM

We performed a case-control study to assess the association between obesity risk and the Trp64Arg polymorphism of the beta 3-adrenergic receptor gene.

METHODS

Obese subjects [n = 159; body mass index (BMI) > 30 kg/m2] and controls (n = 154; BMI < 25 kg/m2) were compared using multivariable logistic regression to control for potential confounders.

RESULTS

A higher obesity risk (adjusted OR: 2.98; 95% CI: 1.00-8.56; p = 0.05) was associated with the Trp64Arg polymorphism among sedentary, but not among more active people.

CONCLUSIONS

Our results suggest that the TRP64ARG polymorphism of the ADRB3 seems to be a risk factor for obesity that is dependent on a sedentary lifestyle.