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PubMed1999

Childhood obesity: the genetic-environmental interface.

Obesity has a high prevalence in children living in industrialized countries. Excess adiposity is the result of a prolonged positive energy balance. Both genetic and environmental factors are involved. A genetic predisposition to obesity has been ascertained from, for example, twin studies. Animal models of genetic obesity have been used to identify candidate genes, which have, in some cases, also been demonstrated in humans. Genome scanning has highlighted some of the human genes that may be involved. Several environmental factors promote an imbalance between nutrient intake and nutrient oxidation in genetically predisposed children. Fat intake is associated with adiposity in children. The low thermogenesis induced by fat intake is another potential contributory factor. Oxidative activity in skeletal muscles greatly influences total energy expenditure as well as fat oxidation rate. Sedentary behaviour promotes low energy requirements in children. Moreover, low skeletal muscle activity reduces fat oxidation, favouring fat gain. Several socio-economic and cultural factors affect the dietary and physical activity habits of children. Finally, the enlargement of the fat mass induces compensatory metabolic reactions to oppose further fat gain. Further research on the factors responsible for the pathogenesis of obesity is necessary to identify more sensitive targets for the effective prevention and treatment of childhood obesity.

Child↗

PubMed1993

Usual dietary fat intake and insulin concentrations in healthy women twins.

OBJECTIVE: To evaluate the associations between the usual intake of dietary fats and insulin concentrations. Insulin concentrations and insulin resistance have been positively related to risk for NIDDM, obesity, hypertension, dyslipidemia, and coronary heart disease, yet little is known of the environmental risk factors for relative hyperinsulinemia. Insulin resistance can be induced by high-fat feeding in laboratory animals; therefore, high-fat diets may increase risks for developing NIDDM. RESEARCH DESIGN AND METHODS: Subjects included 544 nondiabetic women who participated in the second examination of the Kaiser Permanente Women Twins Study (1989-1990). Fasting and 2-h post 75-g glucose load insulin levels were determined. Dietary fat intake was assessed by a food frequency questionnaire. Generalized least-squares regression analyses for unpaired twin data were used to determine the relationship between dietary fat intake and insulin levels after adjustment for total calories, age, several behavioral variables, and in some models, percentage of body fat and waist-to-hip ratio. Associations of dietary fat intake with insulin levels were also evaluated within the subset of monozygotic twin pairs (n = 164 pairs) after removal of genetic influences by regression analysis of intrapair differences. RESULTS: Among the 544 individual women, a 20 g/day increase in total dietary fat was associated with a higher fasting insulin level (9% [P < 0.001] before and 6% [P < 0.01] after adjustment for the obesity variables). Higher intakes of saturated fat, oleic acid, and linoleic acid were each positively related to higher fasting insulin values. The relation of dietary fat with fasting insulin was significantly attenuated among physically active women compared with those who were sedentary (P = 0.04), even after adjustment for obesity. Only saturated fat intake was significantly associated with 2-h postglucose load insulin level before (P = 0.004) but not after adjustment for obesity. Within identical twin pairs, total dietary fat was positively related to fasting insulin before (P = 0.03) but not after adjustment for obesity (P = 0.11). CONCLUSIONS: High intake of total dietary fat is positively related to relative fasting hyperinsulinemia in nondiabetic women, particularly those who are sedentary. This effect appears to be partly mediated by the relation of dietary fat with obesity.

Adult↗

PubMed1984

Contingency management of exercise by chronic schizophrenics.

Research on the control and maintenance of exercise by chronic schizophrenics has been relatively neglected, despite widespread knowledge of the adverse consequences of sedentary living. The present study evaluated the effects of simple contingency-management procedures designed to encourage exercising by two psychotic residents living in a sheltered group home. For both subjects, the ABAB experimental analysis demonstrated the effectiveness of the intervention. Improved levels of exercise were maintained at follow-up and the contingency-management system was implemented as a regular part of the group home's rehabilitation program for all residents.

Adult↗

PubMed1986

Frequency and clustering of nonlipid coronary risk factors in dyslipoproteinemia. The Lipid Research Clinics Program Prevalence Study.

In a defined population of 4349 men and 3398 women, we evaluated the frequency and clustering of five nonlipid coronary heart disease risk factors--obesity, hypertension, sedentary lifestyle, cigarette smoking, and alcohol consumption--in nine categorical lipoprotein phenotypes--normal, types I or V, IIA, IIB, III, IV, hypoHDL (high-density lipoprotein), hypoLDL (low-density lipoprotein), and hyperHDL. This analysis indicated that compared with the normal phenotype, nonlipid coronary risk factors tend to be more frequent and thus cluster in individuals with "high risk" phenotypes, and occur somewhat less frequently in those with "low risk" phenotypes. Thus, identification of a high-risk phenotype suggests the presence of nonlipid risk factors as well, and the clinician should be alert to this possibility. A multivariable analysis of the independent associations of each of the risk factors with the lipid and lipoprotein components that define the phenotypes suggested that several behavioral risk factors may directly affect lipid and lipoprotein levels. This observation raises the possibility that certain intervention strategies, such as weight loss, smoking cessation, and regular exercise, may favorably influence dyslipoproteinemia.

Adult↗

PubMed1994

Determination of the anaerobic threshold by gas exchange: biochemical considerations, methodology and physiological effects.

This paper explains the physiological and biochemical basis of the anaerobic threshold (AT), achieved during physical exercise. The lactate concentration is approximately the same at rest in relatively fit adults, in normal sedentary subjects in adult patients with heart disease. But during exercise, the increase of lactate is inversely related to the physical fitness of the individual. During incremental work, the lactate concentration increases initially very little until a distinct metabolic rate (VO2 AT) is reached at which lactate starts to increase steeply (anaerobic threshold/AT; VO2 AT). Above the anaerobic threshold, accelerated glycolysis increases muscle lactic acidosis. This acidosis is buffered primarily by bicarbonate. The bicarbonate-derived CO2 causes an increased alveolar CO2 output relative to O2 uptake. Oxygen uptake is increased virtually linearly with work rate in healthy subjects with a slope of approximately 10 ml O2/min/Watt. VCO2 starts to increase more steeply in the mid-work-rate range after an initial linear behavior. This steepening is caused by an increased CO2 production from the HCO3-buffering of lactic acid for the range of work rates above the AT. Below the AT, the slope of increase in VCO2 is 1 or slightly less, averaging 0.95. Above the AT, it is greater than 1. The submaximal exercise protocol for the determination of AT includes a period of 2-3 min of unloaded cycling, a ramp program with x Watt increase/minute and a recovery period of 2 min. X is the rate of work rate increase per min, so that the incremental period of the exercise test lasts 8-10 min, stressing the patient for only a short time. The anaerobic threshold can be determined during the ramp program using the following four parameters: 1) steeper increase of VCO2 as compared to VO2 (V-slope-method); 2) respiratory exchange ratio = 0.95; 3) PETO2 increase; 4) VE/VO2 increase. The V-slope-method can be successfully applied, not only in healthy volunteers, but also in patients suffering from cardiac and/or pulmonary (breathing abnormalities) diseases. The so far published data show that the anaerobic threshold in healthy people and patients is a highly reproducible, accurately measurable, securely achievable parameter for the non-invasive evaluation of the individual cardiopulmonary exercise capacity.

Acid-Base Equilibrium↗

PubMed2001

Food and activity preferences in children of lean and obese parents.

BACKGROUND: Children of obese parents have a substantially higher risk of adult obesity than children of lean parents. Adoption and twin studies have shown that this risk is largely genetic but the proximal mechanisms of the genetic risk are not known. Comparisons of energy intake or expenditure in children of obese and lean parents have produced mixed, but generally negative results. An alternative hypothesis is that the early expression of obesity risk is through food and activity preferences, which provides a basis for later weight gain. The aim of this study was therefore to compare food and activity preferences in a large sample of young children from obese and lean families using parental obesity as a marker of the obesity-risk phenotype. Because the children from the families with obese parents were not yet overweight, differences observed in the two types of families are more likely to be causes than effects of obesity. METHODS: A total of 428 children aged 4-5 y, whose parents were either obese/overweight or normal-weight/lean were selected from a population sample of families with twin births. Food and activity preferences were assessed with a combination of food intake and taste tasks, and questionnaires completed by the mother during a home visit. FINDINGS: Children from the obese/overweight families had a higher preference for fatty foods in a taste test, a lower liking for vegetables, and a more 'overeating-type' eating style. They also had a stronger preference for sedentary activities, and spent more time in sedentary pastimes. There were no differences in speed of eating or reported frequency of intake of high-fat foods. CONCLUSION: Part of the process whereby a genetic risk of obesity is transmitted to the next generation could be through differences in diet and activity preferences, which would place susceptible individuals at risk of positive energy balance in the permissive nutritional environment of industrialised countries today.

Child, Preschool↗

PubMed2001

Childhood overweight: a contextual model and recommendations for future research.

The prevalence of overweight among children has doubled within the past two decades. Increases in the rate of childhood overweight are of particular concern due to the negative health and psychological effects noted among overweight children. As shown by previous research, the development of childhood overweight involves a complex set of factors from multiple contexts that interact with each other to place a child at risk of overweight. This multifaceted system can be conceptualized using Ecological Systems Theory (EST). EST highlights the importance of considering the context(s), or ecological niche, in which a person is located in order to understand the emergence of a particular characteristic. In the case of a child, the ecological niche includes the family and the school, which are in turn embedded in larger social contexts including the community and society at large. In this review, EST is used as a framework with which to summarize research assessing predictors of childhood overweight. Specifically, child characteristics that place children at risk of the development of overweight (including dietary intake, physical activity, and sedentary behaviour) will be reviewed while taking into consideration the influence of the familial environment, the school environment, and the community and larger social environments. It is concluded that future research needs to adopt a broader contextual approach in order to understand and intervene against the processes leading to the development of overweight among children and that the use of theories or paradigms such as EST will facilitate developing and testing models of causal processes.

Child↗

PubMed2003

Physical activity interventions in the prevention and treatment of paediatric obesity: systematic review and critical appraisal.

Interventions for prevention and treatment of childhood obesity typically target increases in physical activity and, more recently, reductions in physical inactivity (sedentary behaviour such as television viewing). However, the evidence base for such strategies is extremely limited. The main aim of the present review was to update the systematic review and critical appraisal of evidence in the light of the recent rapid expansion of research in this area. Randomised controlled trials (RCT) that targeted activity or inactivity, that followed up children or adolescents for at least 1 year and that included an objective weight-related outcome measure were included. Trials were appraised using previously published criteria (Harbour & Miller, 2001), and literature search strategies described previously (Reilly et al. 2002) were updated to May 2002. A total of four new RCT, two new systematic reviews and one meta-analysis were identified. The evidence base has increased markedly since the completion of earlier reviews, although high-quality evidence is still lacking. The evidence on childhood obesity prevention is not encouraging, although promising targets for prevention are now clear, notably reduction in sedentary behaviour. There is stronger evidence that targeting activity and/or inactivity might be effective in paediatric obesity treatment, but doubts as to the generalisability of existing interventions, and the clinical relevance of the interventions is unclear. Further research in settings outside the USA is urgently needed, and two ongoing RCT in Scotland are summarised.

Adolescent↗

PubMed2005

Evidence for secular trends in children's physical activity behaviour.

It is not clear whether the global increase in weight problems in children is the result of excessive energy intake or decreasing energy expenditure. Methodological limitations have made it difficult to analyse. There is evidence that at least part of the problem may lie with increasing energy consumption, but it is important to examine the other side of the energy equation also. However, it is not possible to conclusively describe physical activity trends because of the absence of suitable baseline data. One solution is to summate all available evidence in as many areas of daily activities as possible and then draw tentative conclusions. This review summarises available trend data on direct representations of physical activity in a range of contexts, together with indirect measures such as sedentariness, fitness, and attitudes. The conclusions drawn are: physical activity in clearly defined contexts such as active transport, school physical education, and organised sports is declining in many countries; young people would like to be active but are often constrained by external factors such as school policy or curricula, parental rules in relation to safety and convenience, and physical environmental factors.

Activities of Daily Living↗

PubMed1991

Family and peer issues among adolescents with spina bifida and cerebral palsy.

Increasingly, children with disabling conditions are surviving through childhood into adolescence and beyond. This places increased importance on understanding adolescent, family, and peer relationships, which are critical to healthy development among adolescents in general and to transitions to successful adulthood among youths with physical disabilities in particular. The purpose of this study was to identify the patterns of family and peer interactions. One hundred two youths with spina bifida and 60 adolescents with cerebral palsy between the ages of 12 and 22 completed written psychological measures as well as an in-depth structured interview. Approximately 90% of youths with spina bifida and cerebral palsy resided at home, of whom 80.4% and 72% lived with both parents. Almost without exception, parental relationships were defined as positive, with no difference of attitude noted toward the mother and father. Relationships with parents for teenagers with spina bifida were marked by high levels of dependence on parents for personal care such as bowel programs and, for both groups, low levels of responsibility at home and lack of discussion with parents about sexuality or menstruation. Although friends were viewed as very important by most respondents (approximately 83%), relationships were characterized by extremely limited out-of-school contacts, negligible participation with organized social activities, and a primary orientation toward sedentary activities. Finally, regarding heterosexual relationships, whereas 44.1% of respondents with spina bifida and 54.2% of respondents with cerebral palsy said their friends dated, only 14.7% and 28.3% of study participants indicated that they had ever been on a date and, even for those teenagers, heterosexual social contacts were infrequent.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed2004

Differential effects of habitat complexity, predators and competitors on abundance of juvenile and adult coral reef fishes.

Greater structural complexity is often associated with greater abundance and diversity, perhaps because high complexity habitats reduce predation and competition. Using 16 spatially isolated live-coral reefs in the Bahamas, I examined how abundance of juvenile (recruit) and adult (non-recruit) fishes was affected by two factors: (1) structural habitat complexity and (2) the presence of predators and interference competitors. Manipulating the abundance of low and high complexity corals created two levels of habitat complexity, which was cross-factored with the presence or absence of resident predators (sea basses and moray eels) plus interference competitors (territorial damselfishes). Over 60 days, predators and competitors greatly reduced recruit abundance regardless of habitat complexity, but did not affect adult abundance. In contrast, increased habitat complexity had a strong positive effect on adult abundance and a weak positive effect on recruit abundance. Differential responses of recruits and adults may be related to the differential effects of habitat complexity on their primary predators. Sedentary recruits are likely most preyed upon by small resident predators that ambush prey, while larger adult fishes that forage widely and use reefs primarily for shelter are likely most preyed upon by large transient predators that chase prey. Increased habitat complexity may have inhibited foraging by transient predators but not resident predators. Results demonstrate the importance of habitat complexity to community dynamics, which is of concern given the accelerated degradation of habitats worldwide.

Analysis of Variance↗

PubMed2006

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.

Brazil↗

PubMed1996

Psychosocial and physical risk factors for musculoskeletal disorders of the neck, shoulders, and lower back in salespeople.

OBJECTIVES: To analyse the association between symptoms from the musculoskeletal system and many psychosocial and other physical stressors in the job demand-control-support model. Also to analyse the influence of personality characteristics. METHODS: 1306 salespeople answered a self administered questionnaire on job characteristics, exposures, personality characteristics, social network, smoking and drinking habits, and symptoms of the neck, shoulders, and low back. RESULTS: In multivariate analyses, high job demands were related to neck and shoulder symptoms (ORs 1.43-1.47 in the highest exposure groups compared with the lowest), and tendency to become overworked and lack of social support from colleagues were related to back pain (OR 1.81-2.04 in the highest exposure groups compared with the lowest). Lack of variation in the job, low control over time, and high competition were related to neck symptoms, but there was an interaction so that both low control over time and high competition had to be present to increase the OR. Also, driving long distances and sedentary work were related to neck and low back pain, and time spent in the car to shoulder pain (ORs 1.64-2.80 in the three highest groups v the lowest exposure groups). CONCLUSION: Both psychosocial and physical factors were associated with musculoskeletal symptoms. Many dimensions of the demand-control-support model were associated with symptoms. Only one personality characteristic, tendency to feel overworked, significantly influenced the prevalence of musculoskeletal symptoms.

Adult↗

PubMed2006

Participants' perceptions of a lifestyle approach to promoting physical activity: targeting deprived communities in Kingston-upon-Hull.

BACKGROUND: The health benefits of an active lifestyle have been extensively documented and generally accepted. In the UK, declining physical activity levels are a major contributing factor to a number of public health concerns such as obesity and coronary heart disease. Clearly, there is an urgent need to support people in developing sustainable active lifestyles. In 2003, a new lifestyle-based physical activity service called Active Lifestyles (AL) was set up in Kingston-upon-Hull to help local residents to become more active and develop healthier lifestyles. The service targeted the most deprived communities in the city. The aim of the study was to explore participants' perceptions of the operation and effectiveness of the AL service. METHODS: Five focus groups were conducted in community centres and offices in the health promotion service in Kingston-upon-Hull. Sixteen white adult males (n = 5) and females (n = 11) participated in the study. Ages ranged from 15-73 years (mean age = 53 years). Data were analysed using a content analysis technique based on the 'framework' approach. RESULTS: Three broad themes emerged from the focus groups; the referral process; operational aspects of the AL service; and perceived benefits of the service. Overall, participants were extremely positive about the AL service. Many reported increased activity levels, modified eating habits, and enhanced awareness and education regarding healthier living. Most participants reported that local awareness of the AL service was low and greater promotion was required so more people could benefit. The success of the service was highly dependent upon the qualities and approach of the AL advisor. CONCLUSION: The service appears to have filled a gap in service provision since it offered support to the most sedentary, older, unfit and overweight individuals, many of whom live in the most deprived parts of Kingston-upon-Hull. Traditional exercise referral schemes that focus solely on facility-based exercise should be broadened to encompass everyday lifestyle activity, where referral to a gym or exercise facility is just one of a number of physical activity options.

Adolescent↗

PubMed1989

Interactions of iron deficiency and exercise training in male Sprague-Dawley rats: ferrokinetics and hematology.

Ferrokinetic and hematologic studies were performed using adult male Sprague-Dawley rats to determine if 12 wk of exercise training alters the delivery of iron to the red blood cell (RBC) mass, the severity of the anemia or the maximal exercise performance of moderately iron-deficient animals. Forty rats were assigned to either iron-deficient (ID) or control (CN) diets, and further subdivided into sedentary (SD) and exercised (EX) groups. Exercised groups were trained on a treadmill, at a 15% grade, 65% VO2max, for 90 min/d, 4 d/wk. After 12 wk of exercise training and dietary iron deficiency, the final body weight of IDEX rats was 90.5% that of IDSD rats. Fractional plasma iron clearance in IDEX rats was 86% of that in IDSD rats (3.32 vs. 2.85%/min). Exercise training failed to increase absolute VO2max (ml/min) or change hemoglobin concentration in iron-deficient rats. Resting oxygen consumption in IDEX rats was 116% that in IDSD rats (42.8 vs. 32.5 ml.kg-1.min-1, P less than 0.05). We conclude that exercise training and iron deficiency interact to alter iron physiology in exercised, iron-deficient animals. This interaction affects the kinetic behavior of plasma iron, growth and basal oxygen consumption.

Animals↗

PubMed1999

Total daily energy expenditure and patterns of physical activity in adolescents assessed by two different methods.

Minute-by-minute heart rate monitoring and an activity diary were used simultaneously during three days in 30 randomly selected adolescents (16 boys, 14 girls; mean age 15.0+/-1.0). Total daily energy expenditure (TDEE) and its components (energy expenditure during sleep, during rest and in physical activity) and times spent at different intensity levels (sedentary, light, moderate physical activity and vigorous physical activity) were compared. TDEE from heart rate monitoring averaged 10.9+/-2.7 MJ x d(-1) compared to 11.3+/-2.3 MJ x d(-1) from the activity diary (NS). The limits of agreement (mean+/-2 SD) were -3.54 MJ x d(-1) and 2.74 MJ x d(-1). There was no significant difference for any of the TDEE components between the methods (MANOVA). A significant method effect (P<0.001) was observed for time spent in sedentary and light physical activity (MANOVA). No significant difference was observed for time spent in moderate and vigorous physical activity. According to this, heart rate monitoring and activity diary are comparable for group assessment of TDEE and its components, and for estimating time spent in moderate and vigorous physical activity. The activity diary underestimated time spent in moderate and vigorous physical activity for inactive subjects and consequently overestimated highly active subjects.

Adolescent↗

PubMed2000

Comparing physical activity assessment methods in the Seasonal Variation of Blood Cholesterol Study.

PURPOSE: This paper evaluated three measures of physical activity employed in the Seasonal Variation of Blood Cholesterol Study (Seasons), and it had two objectives: 1) To examine the laboratory validity of the Actillume activity monitor, and 2) To examine the relative validity of three 24-h physical activity recalls (24HR) in quantifying short-term physical activity behaviors. METHODS: Nineteen healthy middle-age adults completed seven activity trials (reading, typing, box moving, stepping, and walking (3.5, 4.25, 5.0 km x h(-1))) while oxygen consumption and Actillume measures were obtained. ANOVA, linear regression, and a scatter plot were employed to examine the validity of the Actillume. In relative validity analyses of the 24HR in the Seasons study, participants (N = 481) completed two or three 24HR (MET-h x d(-1)) and a modified Baecke Questionnaire. A subset of the cohort (N = 41) wore the Actillume for 3-8 d (counts x min(-1) x d(-1)). The relative validity of the 24HR method was examined by comparison to these criterion measures. RESULTS: In laboratory validation analyses, the monitor was found to discriminate between sedentary and moderate intensity activities, changes in walking speed, and to account for 79% of the variance in oxygen consumption across sedentary and walking trials. In relative validity analyses, correlations between the 24HR and the modified Baecke ranged from 0.29 to 0.52 (P < 0.01) across total, household, occupational, and leisure-time activities. CONCLUSIONS: In laboratory testing, the Actillume monitor discriminated between sedentary and moderate intensity activities and was highly correlated with oxygen consumption. Three 24HR of physical activity were observed to have a relative validity that was comparable to published data from other short-term activity assessments that also employed the Baecke Questionnaire and activity monitors as criterion measures.

Adult↗

PubMedDate not supplied

Epidemiology of coronary heart disease in women.

Cardiovascular disease (CVD) is the leading cause of mortality in women and a major cause of morbidity. Coronary heart disease (CHD) accounts for nearly half of all CVD deaths. Gender differences in CHD include a later age of onset for women, a greater prevalence of comorbid diseases, and differences in the initial manifestations of the disease. Traditional risk factors for CHD include tobacco use, hypertension, diabetes mellitus, dyslipidemia, obesity, sedentary lifestyle, and atherogenic diet. More recently identified risk factors in women include high sensitivity C-reactive protein (hsCRP), homocysteine, and lipoprotein (a). Appropriate management of risk factors is associated with a reduced incidence of CHD, yet poor implementation in women is widely documented. Barriers to optimal risk factor management in women should be identified and overcome in an effort to maximize the cardiovascular health of women.

Age of Onset↗