The role of exercise in weight regulation in nonathletes

Changes in body composition with a hypocaloric diet combined with sedentary, moderate and high-intense physical activity: a randomized controlled trial

BACKGROUND

There is evidence showing the effectiveness of a hypocaloric diet and the increase in physical activity on weight loss. However, the combined role of these factors, not only on weight loss but also body composition, remains unclear. The purpose of this study was to investigate the effect of a hypocaloric diet on the body composition of obese adult women throughout different degrees of physical activity during a weight loss program.

METHODS

One hundred and seventeen healthy female volunteers were randomly assigned to one of the experimental groups: a control group with a low-level prescription of physical activity (1-4 METs), moderate physical activity group that performed 10.000 steps walking (5-8 METs) and intense physical activity group that trained exercises by at least 70% of VO2max three times a week (> 8 METs). All subjects followed a hypocaloric diet designed with a reduction of 500 kcal/day. Nutritional counseling was provided throughout the study period to help ensure dietary adherence.

RESULTS

We found no differences in body weight compared to moderate and intense physical activity (ßstand. = - 0.138 vs. ßstand. = - 0.139). Body fat was lower in women following an intense activity (ßstand. = - 0.436) than those with moderate exercise (ßstand. = - 0.231). The high-intense activity also increased muscle mass at the end of the intervention, standing out above the moderate activity (ßstand. = 0.182 vs. ßstand. = 0.008).

CONCLUSIONS

These findings indicate that a hypocaloric diet, without prescription of physical activity, is adequate to lose weight in the short term (12 weeks), but physical activity is vital to modify the body composition in women with obesity. Body fat was lower when women practiced a moderate exercise compared to hypocaloric diet only, but an intense physical activity was the most effective protocol to obtain a reduction of body fat and maintain muscle mass.

TRIAL REGISTRATION

The study protocol complied with the Declaration of Helsinki for medical studies, it was approved by the bioethical committee of Córdoba University, in the Department of Health at the Regional Government of Andalusia (Act n°284, ref.4156) and retrospectively registered in clinicaltrials.gov (NCT03833791). Registered 2 January 2019.

Higher Daily Energy Expenditure and Respiratory Quotient, Rather Than Fat-Free Mass, Independently Determine Greater ad Libitum Overeating

CONTEXT

Body fat-free mass (FFM), energy expenditure (EE), and respiratory quotient (RQ) are known predictors of daily food intake. Because FFM largely determines EE, it is unclear whether body composition per se or the underlying metabolism drives dietary intake.

OBJECTIVE

The objective of the study was to test whether 24-hour measures of EE and RQ and their components influence ad libitum food intake independently of FFM.

DESIGN AND PARTICIPANTS

One hundred seven healthy individuals (62 males/45 females, 84 Native Americans/23 whites; age 33 ± 8 y; body mass index 33 ± 8 kg/m(2); body fat 31% ± 8%) had 24-hour measures of EE in a whole-room indirect calorimeter during energy balance, followed by 3 days of ad libitum food intake using computerized vending machine systems. Body composition was estimated by dual-energy x-ray absorptiometry.

MAIN OUTCOME MEASURES

FFM, 24-hour EE, RQ, spontaneous physical activity, sleeping EE (sleeping metabolic rate), awake and fed thermogenesis, and ad libitum food intake (INTAKE) were measured.

RESULTS

Higher 24-hour RQ (P < .001, partial R(2) = 16%) and EE (P = .01, partial R(2) = 7%), but not FFM (P = .65), were independent predictors of INTAKE. Mediation analysis demonstrated that 24-hour EE is responsible for 80% of the FFM effect on INTAKE (44.5 ± 16.9 kcal ingested per kilogram of FFM, P= .01), whereas the unique effect due to solely FFM was negligible (10.6 ± 23.2, P = .65). Spontaneous physical activity (r = 0.33, P = .001), but not sleeping metabolic rate (P = .71), positively predicted INTAKE, whereas higher awake and fed thermogenesis determined greater INTAKE only in subjects with a body mass index of 29 kg/m(2) or less (r = 0.44, P = .01).

CONCLUSIONS

EE and RQ, rather than FFM, independently determine INTAKE, suggesting that competitive energy-sensing mechanisms driven by the preferential macronutrient oxidation and total energy demands may regulate food intake.

Efficacy of WBV as a modality for inducing changes in body composition, aerobic fitness, and muscular strength: a pilot study

The purpose of this pilot study was to evaluate the effectiveness of whole body vibration (WBV) training as a modality for inducing changes in body composition, cardiovascular condition, and muscular strength in sedentary postmenopausal women. WBV training was compared with other training regimens, ie, aerobic training and circuit resistance training, commonly used to promote weight loss, cardiovascular conditioning, and muscular strength. Postmenopausal women (aged 48–60 years) were randomly assigned to WBV training, circuit resistance training, or aerobic training. Participants trained three times per week for 8 weeks. The training regimens were progressive in nature, with increases in training intensity and duration occurring throughout the 8-week period. Body composition was assessed using dual-energy X-ray absorptiometry analyses. A modified Bruce treadmill protocol was used to assess aerobic capacity (VO_2peak) and time to peak exhaustion. Upper and lower body strengths were determined by one repetition maximum (1-RM) chest and leg presses, respectively. Variables were analyzed using separate 3 (exercise mode) × 2 (time) repeated-measures analysis of variance with effect sizes due to the small sample size. No significant main effects or interactions were seen for any body composition variable; however, moderate to large effect sizes (η²=0.243 and η²=0.257) were detected regarding interactions for percent body fat and lean body mass favoring aerobic training and circuit resistance training. For VO_2peak, no significant main effects or interactions were detected (time, η²=0.150; P=0.11; time × group, η²=0.139; P=0.30); but a significant time effect was observed for time to peak exhaustion (η²=0.307; P=0.017). A significant interaction for upper body strength (η²=0.464; P=0.007), and main effect for time in lower body strength (η²=0.663; P=0.0001) was detected. Post hoc analysis indicated a significant increase in upper body strength for circuit resistance training (P=0.023) and a decrease for WBV training (P=0.015). Our results indicate that WBV may not be an effective alternative to traditional training with regard to body composition or aerobic capacity, but could have a positive impact on lower body strength.

Pragmatic randomised trial of a 12-week exercise and nutrition program for Aboriginal and Torres Strait Islander women: clinical results immediate post and 3 months follow-up

Background

Aboriginal and Torres Strait Islander women experience higher rates of heart disease and type 2 diabetes than non-Indigenous Australian women. Increasing physical activity, improving diets and losing weight have been shown to reduce cardio metabolic risk. The primary aim was to evaluate the effectiveness of a 12-week structured exercise and nutrition program in a cohort of urban Indigenous Australian women on waist circumference, weight and biomedical markers of metabolic functioning from baseline (T1) to program completion (T2). The secondary aim assessed whether these outcomes were maintained at 3-month follow-up.

Methods

One hundred Aboriginal and/or Torres Strait Islander women aged 18–64 years living in the Adelaide metropolitan area were recruited. The program included two 60-minute group cardiovascular and resistance training classes per week, and four nutrition education workshops. Participants were randomly assigned to an ‘active’ group or ‘waitlisted’ control group. Body weight, height, waist and hip circumference, blood pressure, fasting glucose, fasting insulin, glycated haemoglobin (HbA1C), lipid profile and C-reactive protein (CRP) were assessed at baseline (T1), immediately after the program (T2) and three months post program (T3).

Results

The active group showed modest reductions in weight and body mass index (BMI). Compared to the waitlisted group, the active group had a statistically significantly change in weight and BMI from baseline assessments; at T2, ^-1.65 kg and ^-0.66 kg/m² and at T3, ^-2.50 kg and ^-1.03 kg/m², respectively. Systolic and diastolic blood pressure also had a statistically significant difference from baseline in the active group compared to the waitlisted group at T2, ^-1.24 mmHg and ^-2.46 mmHg and at T3, ^-4.09 mmHg and ^-2.17 mmHg, respectively. The findings were independent of the baseline measure of the outcome variable, age, households with children and employment status. Changes in waist circumference and other clinical measures were not significant at T2 or T3. The primary outcome measure, waist circumference, proved problematic to assess reliably. Missing data and participants lost to follow-up were significant.

Conclusions

This 12-week exercise program demonstrated modest reductions in weight, BMI and blood pressure at T2, which improved further at 3-month follow-up (T3). Positive intervention effects were observed despite low attendance at exercise classes. Structured exercise programs implemented in community settings require attention to understanding the barriers to participation for this high risk group.

Trial registration

Australian New Zealand Clinical Trials Registry ACTRN12610000224022

Physical activity and gynecologic cancer prevention

This chapter reviews the findings from epidemiologic studies of the associations of physical activity with gynecologic cancers, including those of the endometrium, ovaries, and cervix, and the biologic mechanisms mediating the associations. The epidemiologic evidence to date suggests that physical activity probably protects against endometrial cancer, with a risk reduction of about 20-30% for those with the highest levels of physical activity compared to those with the lowest levels, and that light to moderate physical activity including housework, gardening, or walking for transportation may reduce risk. The role of physical activity in ovarian cancer development remains uncertain, as findings from these studies have been inconsistent with about half the studies suggesting physical activity modestly decreases risk and about half the studies suggesting no association. A recent meta-analysis of studies examining recreational physical activity with ovarian cancer risk estimated a 20% reduced risk for the most active versus least active women. There is mounting evidence that sedentary behaviors such as sitting time probably increase risk of endometrial and ovarian cancers. Overall, there is insufficient evidence to draw a conclusion on a possible role of physical activity in the development of cervical cancer, although a modest influence on risk is possible through effects on sex steroid hormones and immune function. The biologic evidence provides strong support for a protective role of physical activity on cancer of the endometrium, and moderate support for cancer of the ovaries, as these cancers have a strong hormonal etiology. The more established biologic mechanisms that are supported by epidemiologic and experimental data involve endogenous sex hormone levels, insulin-mediated pathways, and maintenance of energy balance.In this chapter, we will discuss the evidence for an association of physical activity with gynecologic cancers including those of the endometrium, ovaries, and cervix. Cancers of the endometrium and ovaries have a strong hormonal etiology (Risch 1998; Kaaks et al. 2002; Lukanova and Kaaks 2005), and physical activity has been postulated as a potential modifiable risk factor for prevention of these cancers because it can influence circulating hormone levels, energy balance, and insulin-mediated pathways that are thought to be important mediators underlying the associations. Few studies have evaluated the association of physical activity with cervical cancer because the main causal factor is infection with certain types of human papillomavirus (HPV), although other hormonal and immune factors are also thought to play a role (Smith et al. 2003; Waggoner 2003). We review the findings from epidemiologic studies that have examined the associations of physical activity with gynecologic cancers, and the biologic mechanisms that might mediate the associations.

Adiposity changes after a 1-year aerobic exercise intervention among postmenopausal women: a randomized controlled trial

Objective:

We examined the effects of an aerobic exercise intervention on adiposity outcomes that may be involved in the association between physical activity and breast cancer risk.

Design:

This study was a two-centre, two-armed, randomized controlled trial. The 1-year-long exercise intervention included 45 min of moderate-to-vigorous aerobic exercise five times per week, with at least three of the sessions being facility based. The control group was asked not to change their activity and both groups were asked not to change their diet.

Subjects:

A total of 320 postmenopausal, sedentary, normal weight-to-obese women aged 50–74 years who were cancer-free, nondiabetic and nonhormone replacement therapy users were included in this study.

Measurements:

Anthropometric measurements of height, weight and waist and hip circumferences; dual energy X-ray absorptiometry measurements of total body fat; and computerized tomography measurements of abdominal adiposity were carried out.

Results:

Women in the exercise group exercised a mean of 3.6 days (s.d.=1.3) per week and 178.5 min (s.d.=76.1) per week. Changes in all measures of adiposity favored exercisers relative to controls (P<0.001). The mean difference between groups was: −1.8 kg for body weight; −2.0 kg for total body fat; −14.9 cm² for intra-abdominal fat area; and −24.1 cm² for subcutaneous abdominal fat area. A linear trend of greater body fat loss with increasing volume of exercise was also observed.

Conclusion:

A 1-year aerobic exercise program consistent with current public health guidelines resulted in reduced adiposity levels in previously sedentary postmenopausal women at higher risk of breast cancer.

Physical activity patterns and prevention of weight gain in premenopausal women

BACKGROUND

Studies of the association between physical activity (PA) and weight maintenance have been inconsistent.

METHODS

We prospectively examined the association between PA patterns and prevention of weight gain among 46,754 healthy premenopausal women, aged 25–43 years in 1989. Participants reported their PA and weight in 1989 and 1997. The primary outcome was gaining >5% of baseline weight by 1997 (62% of the population).

RESULTS

Compared with women who maintained <30 minutes/day of total discretionary activity over 8 years, women were less likely to gain weight if they sustained 30+ minutes/day (Odds Ratio OR=0.68, 95% confidence interval [CI] 0.64–0.73) or increased to 30+ minutes/day in 1997 (OR=0.64, 95%CI=0.60–0.68). Among women whose only reported activity was walking, risk of gaining weight was lower in those who sustained 30+ minutes/day over 8 years (OR=0.66, 95%CI=0.49–0.91), and brisk walking pace independently predicted less weight gain. For a 30 minutes/day increase between 1989 and 1997, jogging/running was associated with less weight gain than brisk walking or other activities. Greater duration of PA was associated with progressively less weight gain, but even an 11–20 minutes/day increase was beneficial; the benefits appeared stronger among those initially overweight. Sedentary behavior independently predicted weight gain.

CONCLUSIONS

Sustained PA for at least 30 minutes/day, particularly if more intense, is associated with a reduction in long-term weight gain, and greater duration is associated with less weight gain. Sedentary women of any baseline weight who increase their PA will benefit, but overweight women appear to benefit the most.

A meta-analysis of pedometer-based walking interventions and weight loss

PURPOSE

Cross-sectional studies show that individuals who walk more tend to be thinner than those who walk less. This does not mean, however, that the association between higher step counts and lower weight is causal or that encouraging sedentary individuals to increase step counts helps them lose weight.

METHODS

In this meta-analysis, we searched 6 electronic databases and contacted pedometer experts to identify pedometer-based walking studies without a dietary intervention that reported weight change as an outcome. We included randomized controlled trials and prospective cohort studies published after January 1, 1995, in either English or Japanese, with 5 or more adult participants and at least 1 cohort enrolled in a pedometer-based walking intervention lasting at least 4 weeks.

RESULTS

Nine studies met the study inclusion criteria. Cohort sample size ranged from 15 to 106, for a total of 307 participants, 73% of whom were women and 27% of whom were men. The duration of the intervention ranged from 4 weeks to 1 year, with a median duration of 16 weeks. The pooled estimate of mean weight change from baseline using a fixed-effects model and combining data from all 9 cohorts was -1.27 kg (95% confidence interval, -1.85 to -0.70 kg). Longer intervention duration was associated with greater weight change. On average, participants lost 0.05 kg per week during the interventions.

CONCLUSION

Pedometer-based walking programs result in a modest amount of weight loss. Longer programs lead to more weight loss than shorter programs.

Physical activity and endometrial cancer risk: a review of the current evidence, biologic mechanisms and the quality of physical activity assessment methods

OBJECTIVES

To (1) determine the nature of the association between physical activity and endometrial cancer risk; (2) assess the contribution of variation in the quality of physical activity measurement to inconsistencies in study results; and (3) review the biologic mechanisms that might mediate possible effects of physical activity on risk.

METHODS

We reviewed and summarized all published epidemiologic studies examining physical activity and endometrial cancer risk, and evidence relating to possible biologic mechanisms. We assigned each study a quality score for physical activity measurement.

RESULTS

Fourteen of the 18 studies showed a convincing or possible protective effect of physical activity on endometrial cancer risk, with an average relative risk reduction of around 30%. A dose-response relation was observed in 7 of 13 studies. The quality score was not related to the observed strength of association or the presence of a dose-response relation. There was epidemiologic and biologic evidence that vigorous activity, as well as light and moderate intensity activities, such as housework, gardening or walking for transportation, may reduce risk.

CONCLUSIONS

Physical activity probably has a protective role in endometrial cancer development. More epidemiologic and biologic evidence is needed to make conclusive recommendations on optimal types, characteristics or time periods of physical activity.

The effects of exercise on body weight and composition in breast cancer survivors: an integrative systematic review

PURPOSE/OBJECTIVES

To examine the research literature regarding the effects of exercise on body weight and composition in breast cancer survivors.

DATA SOURCES

Primary studies in English published from 1989-2004, located through electronic databases, hand searches, and personal contacts.

DATA SYNTHESIS

Of 1,314 studies screened, 14 met all inclusion criteria. Body weight and composition generally were secondary endpoints. Effects on weight were less common than reduction in percentage of body fat.

CONCLUSIONS

The evidence regarding exercise as a strategy for body weight and composition management in breast cancer is sparse. Research that considers these outcomes as primary endpoints is needed. Numerous measurement issues need to be addressed in future studies.

IMPLICATIONS FOR NURSING

Exercise may help to control adverse body weight and composition changes among breast cancer survivors. Improved research that assigns these outcomes primary importance will greatly enhance clinicians' ability to assist women in body weight and composition management.

Feasibility of adding enhanced pedometer feedback to nutritional counseling for weight loss

Background

Intensive interventions targeting diet and physical activity are effective for weight reduction but are costly. Tailored, computer-generated, step-count feedback may provide an intensive and affordable way to increase the physical activity of people at high risk for cardiovascular disease.

Objective

The objective was to test the feasibility of adding tailored, computer-generated, step-count feedback to a face-to-face nutritional counseling weight loss intervention.

Methods

We recruited 12 participants, 4 from each of three Department of Veterans Affairs medical centers. There were 11 male participants and 1 female participant. Each had a body mass index of 30 or greater and at least one of the following cardiovascular disease risk factors: diabetes, hypertension, hypercholesterolemia, obesity, or coronary artery disease. Participants attended one-on-one counseling sessions with a registered dietitian for four sessions over three weeks. At the initial session, each participant received an enhanced pedometer to record time-stamped, step-count data. Participants wore the device daily throughout the intervention. At the three follow-up sessions, the dietitian uploaded the computer data, reviewed a Web-based graphical display of step-count feedback, and helped set new walking goals.

Results

All 12 participants completed the program (100% attendance). Initial mean weight was 255 lbs (SD = 49 lbs), and weight loss was just over 4 lbs (n = 12, paired t test, P = .004). Mean daily step counts during the first week averaged 6019 steps per day, increasing to an average of 7358 per day after the third week (average increase of 1339 steps per day, or 0.6 miles, or 12 minutes of walking, n = 10, paired t test, P = .04).

Conclusions

Enhanced pedometer feedback in conjunction with nutritional counseling is feasible and results in significant weight loss and increased walking among individuals at high risk for cardiovascular disease.

Obesity - an epidemic of the twenty-first century: an update for psychiatrists

Obesity is a chronic relapsing condition associated with significant morbidity and premature mortality. The prevalence of obesity has increased dramatically over the last 20 years and continues to do so, primarily as a result of changes in dietary intake and exercise patterns. There are considerable challenges associated with the management of the obesity epidemic involving both public health policies and individual treatment. Management of the obese individual involves lifelong lifestyle change for all, drugs for some, and surgery for a few. Appropriate selection of patients and the setting of realistic goals are crucial to the success of any weight-reducing programme. The aim of obesity management is to reduce associated morbidity and mortality, not necessarily to restore normal body weight. While the current trends in obesity are depressing, a better understanding of the pathophysiology and treatment of the condition should allow the clinician to be more optimistic for the future.

Increasing lifestyle physical activity in patients with depression or other serious mental illness

People with severe and persistent mental illness are more likely to be overweight and to suffer from obesity-related illnesses such as diabetes and heart disease than healthy individuals. Lifestyle change interventions that emphasize integrating physical activity into daily life have not been studied extensively in people with mental illness. The authors present the results of an initial feasibility study of a lifestyle modification program for individuals with serious mental illness. Thirty-nine individuals with depression or other serious mental illness were recruited from three different mental health facilities to attend an 18-week lifestyle intervention program promoting physical activity and healthy eating. At each session, participants discussed topics related to healthy lifestyle changes and participated in group walks. Data were collected at baseline, 6 weeks, and 18 weeks. The results demonstrated that individuals who have depression and other serious mental illnesses can participate in a lifestyle intervention program. Participants who attended the final follow-up session had lost weight over the course of the intervention. Study retention was a problem. However, the cost of this type of group-based lifestyle intervention was relatively low, so that such an intervention for this high-risk group may still be cost-effective.

Physical Activity Profiles of U.S. Adults Trying to Lose Weight: NHIS 1998

PURPOSE

Physical activity is an integral part of weight control programs, but recommended amounts vary. The objectives of this study were to describe the prevalence and characteristics of those who reported using exercise as a weight loss strategy (N=14,716), and to determine the prevalence of meeting various institutionally recommended levels of physical activity (N=8538) among that population.

METHODS

Data were obtained from the 1998 National Health Interview Survey, a face-to-face nationally representative household interview. Questions on leisure-time physical activity were analyzed using SUDAAN.

RESULTS

Among those who reported trying to lose weight, 55% reported using exercise as a weight loss strategy alone, and of those, 58% reported eating fewer calories. The prevalence of using exercise as a weight loss strategy was directly associated with education and inversely associated with age and body mass index. Among those who reported using exercise as a weight loss strategy, 57% met the minimal 1998 National Institutes of Health recommendation of >or=150 min.wk; 46% met the lower end of the 2001 American College of Sports Medicine recommendation of 200 min.wk; and 30% met the upper end for 300 min.wk. Only 19% met the 2002 Institute of Medicine recommendation of 420 min.wk.

CONCLUSIONS

Despite the importance of physical activity in a weight loss program, only about half of the persons trying to lose weight reported using exercise. Even among those, only slightly more than half met the minimal recommendations for physical activity. Efforts are needed to aid those trying to lose weight to incorporate appropriate levels of physical activity into their weight loss strategy.

Preventing macrovascular disease in patients with type 2 diabetes mellitus

Type 2 diabetes mellitus (DM) is associated with an increased risk for both micro-and macrovascular complications, and cardiovascular diseases (CVD) are the most common causes of death in these patients, accounting for almost 70% of the deaths. Given the high prevalence of the condition and the expected global increase in the prevalence of type 2 DM, a case is made for prevention of these serious complications in order to reduce the individual morbidity and the economic burden on society. In this review we present the knowledge of how macrovascular disease in patients with type 2 DM may be prevented, and suggest possible strategies for doing so.A thorough search of the published literature was conducted and we first present relevant epidemiological studies demonstrating the impact of important risk factors for CVD in DM, such as dyslipidemia, hyperglycemia, hypertension, smoking, familial premature coronary heart disease and some non-classical risk factors such as hyperinsulinemia, insulin resistance, endothelial dysfunction and inflammation. Secondly, we review the results from published randomized controlled clinical trials and meta-analysis of these, evaluate the findings and suggest strategies for preventing CVD in patients with type 2 DM using non-pharmacological and pharmacological approaches. Present knowledge indicates that most patients with type 2 DM either have manifest CVD or have a high risk for future cardiovascular events, men with DM have a 2- to 4-fold; and women with DM a 3- to 5-fold increased risk for cardiovascular death compared with non-diabetic individuals. Care of patients with type 2 DM should include yearly risk assessment by the use of published risk equations or risk charts. On the background of this assessment, an individual risk reducing strategy should be tailored to each patient's need, including the treatment of hyperglycemia, hypertension and dyslipidemia together with the use of aspirin (acetylsalicylic acid) and ACE inhibitors. Such measures can reduce the risk of cardiovascular events in patients with type 2 DM.

The relationship of physical activity with dietary cancer-protective nutrients and cancer-related biological and lifestyle factors

The aim of the present study was to analyse the relationships among different intensities of leisure-time physical activity (PA) and cancer-protective dietary components, cancer-related biological (general and central obesity) and lifestyle factors (heavy smoking and excessive alcohol consumption). The present population-based cross-sectional study (765 men and 812 women from the general population of Gerona, Spain) included measurement of anthropometrical data, dietary intake, and alcohol and cigarette consumption and furthermore detailed evaluation of total leisure-time physical activity, including measurement of different intensities. Logistic regression analysis adjusted for several confounders was used to analyse the relationships among variables. A composite variable composed of dietary fibre, vitamin C, alpha-tocopherol, beta-carotene and folate was directly associated with higher levels of leisure-time PA in both genders, after further adjusting for energy intake [odds ratio (OR) of low versus second tertile of total leisure-time PA was 1.98 (95% confidence interval (CI) 1.22-3.23) for men and OR of low versus top tertile of total leisure-time PA was 1.75 (95% CI 1.07-2.84) for women]. Low to moderate- but not high-intensity leisure-time PA was directly related to higher intakes of these nutrients. Heavy smoking was inversely associated with higher levels of total leisure-time PA in men. With the exception of central obesity in women, there was no significant relationship between the cancer-related biological and lifestyle factors, and low to moderate-intensity leisure-time PA in both genders. In contrast, central obesity (OR 0.31, 95% CI 0.16-0.63) and heavy smoking (OR 0.38, 95% CI 0.16-0.96) were significantly related to high-intensity but not to total or low to moderate-intensity leisure-time PA in men and women, respectively. The observed relationships between leisure-time PA and several of the studied cancer-associated variables might partially account for the protective effect of physical activity against cancer observed in the literature. However, different intensities of leisure-time PA were distinctly associated with the mentioned cancer-related dietary, biological and lifestyle factors. Most importantly, although some of these variables were not associated with total leisure-time PA a significant relationship was observed for intensities of leisure-time PA. This should be considered when analysing the relationship between leisure-time PA and cancer.

[Presence of genu valgum in obese children: cause or effect?]

BACKGROUND

Changes in body configuration that may affect the physical activity may play a role in the caloric consumption and led to the development of obesity.

OBJECTIVES

To determine the presence of genu valgum, an alteration that may decrease physical activity and caloric expenditure, in overweight children.

METHODS

Thirty-five overweight children without any endocrinological alterations that could lead to obesity were studied. Twenty-nine non-overweight children of a similar age were studied as a control group. In all children weight, height, and body mass index (BMI) were studied, and intermalleolar distance was used to measure the degree of genu valgum. The differences between groups were studied using ANOVA and the correlation between variables was determined using Pearson's correlation.

RESULTS

BMI was higher in overweight children than in the control group. Intermalleolar distance was greater in overweight children than in the non-overweight group (11.0 0.6 vs 2.90 0.43; p < 0.001). A positive correlation between the intermalleolar distance and the BMI was observed in the overweight group (p < 0.009). Fifty percent of the overweight children showed an intermalleolar distance of more than 10 cm, a value considered abnormal.

CONCLUSIONS

The incidence of genu valgum is much higher in overweight children than in non-overweight children of the same age. This alteration may lead to decreased physical activity and lead to obesity.

The independent and combined effects of 16 weeks of vigorous exercise and energy restriction on body mass and composition in free-living overweight men--a randomized controlled trial

This study assessed the effects of 16 weeks of energy restriction and vigorous exercise on body mass and body composition. Sixty sedentary men, mean body mass (mean +/- SD) 96.3 (13.9) kg and mean age 42.4 (5.0) years, were randomly assigned to either continue their normal energy intake or restrict energy intake by 4,186 to 6,279 kJ. d(-1). Each group was further randomized to a control light exercise program, or a vigorous exercise program for 3 half-hour sessions per week. Vigorous exercise improved maximum oxygen consumption (Vo(2max)) by approximately 24% (0.56 [95% confidence interval, 0.47 to 0.65) L. min(-1), P <.001) with no significant changes in body mass, body composition, or fat distribution. With energy restriction there was a significant reduction in body mass of 10.1 (8.0 to 12.2) kg, lean body mass (LBM) of 2.4 (1.5 to 3.3) kg, fat mass (FM) of 7.7 (5.9 to 9.6) kg, waist to hip ratio (WHR) of 0.03 (0.01 to 0.04), and the sum of 6 skinfolds of 26.9 (15.4 to 38.4) mm (P <.001). Combining vigorous exercise with energy restriction resulted in no further changes in measures of body composition. We conclude that in sedentary free-living overweight men, 16 weeks of energy restriction, but not vigorous intensity exercise, results in substantial reductions in body mass, LBM, and FM. Furthermore, vigorous intensity exercise when combined with energy restriction did not modify or enhance the changes in body fat distribution or body composition seen with energy restriction alone. The independent effects of exercise to induce changes in body mass and composition in the longer term in free-living overweight subjects on an energy-restricted diet deserve further study.

Effects of moderate-intensity exercise on physiological, behavioral, and emotional responses to family caregiving: a randomized controlled trial

BACKGROUND

The study objective was to determine the health and quality-of-life effects of moderate-intensity exercise among older women family caregivers.

METHODS

This 12-month randomized controlled trial involved a volunteer sample of 100 women aged 49 to 82 years who were sedentary, free of cardiovascular disease, and caring for a relative with dementia. Participants were randomized to 12 months of home-based, telephone-supervised, moderate-intensity exercise training or to an attention-control (nutrition education) program. Exercise consisted of four 30- to 40-minute endurance exercise sessions (brisk walking) prescribed per week at 60% to 75% of heart rate reserve based on peak treadmill exercise heart rate. Main outcomes were stress-induced cardiovascular reactivity levels, rated sleep quality, and reported psychological distress.

RESULTS

Compared with nutrition participants (NU), exercise participants (EX) showed significant improvements in the following: total energy expenditure (baseline and post-test means [SD] for EX = 1.4 [1.9] and 2.2 [2.2] kcal/kg/day; for NU = 1.2 [1.7] and 1.2 [1.6] kcal/kg/day; p <.02); stress-induced blood pressure reactivity (baseline and post-test systolic blood pressure reactivity values for EX = 21.6 [12.3] and 12.4 [11.2] mm Hg; for NU = 17.9 [10.2] and 17.7 [13.8] mm Hg; p <.024); and sleep quality (p <.05). NU showed significant improvements in percentages of total calories from fats and saturated fats relative to EX (p values <.01). Both groups reported improvements in psychological distress. Conclusions. Family caregivers can benefit from initiating a regular moderate-intensity exercise program in terms of reductions in stress-induced cardiovascular reactivity and improvements in rated sleep quality.

Effects of two frequencies of walking on cardiovascular risk factor reduction in Mexican American women

The beneficial effects of moderate-intensity exercise on cardiorespiratory fitness and body composition are well documented, with the greatest health benefits reported in sedentary individuals who engage in moderate levels of exercise. The published literature contains no quantification of the threshold of lower limits of beneficial exercise or estimates of benefits derived from lower exercise levels. The specific aim of this study was to compare the effects of two walking frequencies, holding intensity and duration constant, on blood lipids, body composition, and exercise maintenance regimens of Mexican American women. A quasi-experimental design, with two treatment groups and one comparison group, was used to explore the dose-response effects of low-intensity exercise on cardiovascular outcomes. Significant interactions were found between walking and total serum cholesterol and skin-fold sums. This study demonstrated the clinical efficacy of a low-intensity exercise regimen on cardiovascular risk factors and exercise adherence.

Exercise and diabetes

As rates of diabetes mellitus and obesity continue to increase, physical activity continues to be a fundamental form of therapy. Exercise influences several aspects of diabetes, including blood glucose concentrations, insulin action and cardiovascular risk factors. Blood glucose concentrations reflect the balance between skeletal muscle uptake and ambient concentrations of both insulin and counterinsulin hormones. Difficulties in predicting the relative impact of these factors can result in either hypoglycemia or hyperglycemia. Despite the variable impact of exercise on blood glucose, exercise consistently improves insulin action and several cardiovascular risk factors. Beyond the acute impact of physical activity, long-term exercise behaviors have been repeatedly associated with decreased rates of type 2 diabetes. While exercise produces many benefits, it is not without risks for patients with diabetes mellitus. In addition to hyperglycemia, from increased hepatic glucose production, insufficient insulin levels can foster ketogenesis from excess concentrations of fatty acids. At the opposite end of the glucose spectrum, hypoglycemia can result from excess glucose uptake due to either increased insulin concentrations, enhanced insulin action or impaired carbohydrate absorption. To decrease the risk for hypoglycemia, insulin doses should be reduced prior to exercise, although some insulin is typically still needed. Although precise risks of exercise on existing diabetic complications have not been well studied, it seems prudent to consider the potential to worsen nephropathy or retinopathy, or to precipitate musculoskeletal injuries. There is more substantive evidence that autonomic neuropathy may predispose patients to arrhythmias. Of clear concern, increased physical activity can precipitate a cardiac event in those with underlying CAD. Recognizing these risks can prompt actions to minimize their impact. Positive actions that are part of exercise programs for diabetic patients emphasize SMBG, foot care and cardiovascular functional assessment. SMBG provides critical information on the impact of exercise and is recommended for all patients before, during and after exercise. More frequent monitoring (and for longer periods following exercise) is recommended for those with hypoglycemia unawareness or those performing high-intensity exercise. Preventing the sequelae of an exercise-induced severe hypoglycemic reaction can be as simple as carrying glucose tablets or gel, a diabetic identification bracelet or card, or exercising with an individual who is aware of the circumstances. In addition to blood glucose concentrations, proper foot care is critical to people with diabetes who exercise and includes considering type of shoe, type of exercise, inspection of skin surfaces and appropriate evaluation and treatment of lesions (calluses and others). Those with severe neuropathy can consider alternatives to weight-bearing exercises. Precipitation of clinical CAD is of great concern for all diabetic patients participating in exercise activities. Although a sufficiently sensitive and specific screening test for coronary disease has not been identified, those planning an exercise program of moderate intensity or greater should be evaluated. Initial cardiac assessment should include exercise testing as well as identifying risk for autonomic neuropathy. In addition to noting maximal heart rate and blood pressure as well as ischemic changes, exercise tolerance testing can identify anginal thresholds and patients with asymptomatic ischemia. Those without symptoms should be counseled regarding target pulse rates to avoid inducing ischemia. Ischemic changes need to be evaluated for either further diagnostic testing or pharmacological intervention. For patients with diabetes mellitus, the overall benefits of exercise are clearly significant. Clinicians and patients must work together to maximize these benefits while minimizing risks for negative consequences. Identifying and preventing potential problems beforehand can reduce adverse outcomes and promote this important approach to healthy living.

The behavioral determinants of exercise: implications for physical activity interventions

In light of the well-documented health benefits of physical activity and the fact that the majority of adult men and women are inactive, promoting regular physical activity is a public health priority. This chapter reviews current research findings regarding the determinants of exercise behavior. It also discusses the implications of this knowledge for individual and public health recommendations and intervention strategies for promoting physical activity. The discussion is predicated on the belief that physical activity is a complex, dynamic process. During their lives, individuals typically move through various phases of exercise participation that are determined by diverse factors. This chapter discusses physical activity determinants in two broad categories: individual characteristics, including motivations, self-efficacy, exercise history, skills, and other health behaviors; and environmental characteristics such as access, cost, and time barriers and social and cultural supports.

Exercise and obesity

The prevalence of obesity has increased dramatically during the past decade in the USA. This is despite an estimated 50 million Americans who try to lose weight each year. The increasing prevalence of obesity is particularly alarming due to the numerous health implications associated with this condition, including coronary artery disease, hypertension, diabetes, hyperlipidemia, cancer, and various musculoskeletal conditions. The economic impact of treating illnesses associated with obesity has been estimated to be US$40 billion in the USA. Dieting is largely ineffective in maintaining initial weight loss as numerous studies suggest the majority of dieters regain all lost weight with 3-5 years. On, the other hand, regular exercise has been shown to be one of the best predictors of successful weight maintenance. Moreover, studies indicate that improved fitness through regular physical activity reduces cardiovascular morbidity and mortality for overweight individuals even if they remain overweight. Providing advice about exercise to overweight or obese individuals requires explicit information about the frequency, intensity, duration, and type of physical activity that should be performed. The ultimate goal for the exercising obese patient is to make a life-long commitment to achieving reasonable energy expenditure through routine physical activity.

How effective are traditional dietary and exercise interventions for weight loss?

Health care professionals have used restrictive dieting and exercise intervention strategies in an effort to combat the rising prevalence of obesity in affluent countries. In spite of these efforts, the prevalence of obesity continues to rise. This apparent ineffectiveness of diet and exercise programming to reduce obesity has caused many health care providers, obesity researchers, and lay persons to challenge the further use of diet and exercise for the sole purpose of reducing body weight in the obese. The purposes of this paper were to examine the history and effectiveness of diet and exercise in obesity therapy and to determine the best future approach for health promotion in the obese population. A brief survey of the most popular dieting techniques used over the past 40 yr shows that most techniques cycle in and out of popularity and that many of these techniques may be hazardous to health. Data from the scientific community indicate that a 15-wk diet or diet plus exercise program produces a weight loss of about 11 kg with a 60-80% maintenance after 1 yr. Although long-term follow-up data are meager, the data that do exist suggest almost complete relapse after 3-5 yr. The paucity of data provided by the weight-loss industry has been inadequate or inconclusive. Those who challenge the use of diet and exercise solely for weight control purposes base their position on the absence of weight-loss effectiveness data and on the presence of harmful effects of restrictive dieting. Any intervention strategy for the obese should be one that would promote the development of a healthy lifestyle. The outcome parameters used to evaluate the success of such an intervention should be specific to chronic disease risk and symptomatologies and not limited to medically ambiguous variables like body weight or body composition.

Factors associated with physical activity in women across the life span: implications for program development

This study examined the rates and factors associated with physical activity in women of various ages. Adult women (n = 653) from four community-based family medicine clinics completed a self-administered behavioral and health questionnaire while waiting to see their physician. Findings suggested variation in physical activity over the life span, with older women performing less physical activity than younger women. Family characteristics (e.g., having children) were strongly associated with performing less structured, less intense physical activities of daily living among women 49 years and younger. Younger women reported having high self-efficacy for physical activity, but also reported the greatest numbers of barriers. Women in the oldest age category reported health as the most common motivator for physical activity, but were also least likely to perform physical activity. Interventions designed to meet the unique needs of women at different stages in their lives will potentially reduce the rate of inactivity among women. Creative, flexible strategies that incorporate physical activity into the daily routine should be used in the program development.

Who walks? Factors associated with walking behavior in disabled older women with and without self-reported walking difficulty

OBJECTIVES

To determine how severity of walking difficulty and sociodemographic, psychosocial, and health-related factors influence walking behavior in disabled older women.

DESIGN

Cross-sectional analyses of baseline data from the Women's Health and Aging Study (WHAS).

SETTING

An urban community encompassing 12 contiguous zip code areas in the eastern portion of Baltimore City and part of Baltimore County, Maryland.

PARTICIPANTS

A total of 920 moderately to severely disabled community-resident women, aged 65 years and older, identified from an age-stratified random sample of Medicare beneficiaries.

MEASUREMENTS

Walking behavior was defined as minutes walked for exercise and total blocks walked per week. Independent variables included self-reported walking difficulty, sociodemographic factors, psychological status (depression, mastery, anxiety, and cognition), and health-related factors (falls and fear of falling, fatigue, vision and balance problems, weight, smoking, and cane use).

RESULTS

Walking at least 8 blocks per week was strongly negatively related to severity of walking difficulty. Independent of difficulty level, older age, black race, fatigue, obesity, and cane use were also negatively associated with walking; living alone and high mastery had a positive association with walking.

CONCLUSIONS

Even among functionally limited women, sociocultural, psychological, and health-related factors were independently associated with walking behavior. Thus, programs aimed at improving walking ability need to address these factors in addition to walking difficulties to maximize participation and compliance.

Effects of resistance vs. aerobic training combined with an 800 calorie liquid diet on lean body mass and resting metabolic rate

OBJECTIVE

Utilization of very-low-calorie diets (VLCD) for weight loss results in loss of lean body weight (LBW) and a decrease in resting metabolic rate (RMR). The addition of aerobic exercise does not prevent this. The purpose of this study was to examine the effect of intensive, high volume resistance training combined with a VLCD on these parameters.

METHODS

Twenty subjects (17 women, three men), mean age 38 years, were randomly assigned to either standard treatment control plus diet (C+D), n = 10, or resistance exercise plus diet (R+D), n = 10. Both groups consumed 800 kcal/day liquid formula diets for 12 weeks. The C+D group exercised 1 hour four times/week by walking, biking or stair climbing. The R+D group performed resistance training 3 days/week at 10 stations increasing from two sets of 8 to 15 repetitions to four sets of 8 to 15 repetitions by 12 weeks. Groups were similar at baseline with respect to weight, body composition, aerobic capacity, and resting metabolic rate.

RESULTS

Maximum oxygen consumption (Max VO2) increased significantly (p<0.05) but equally in both groups. Body weight decreased significantly more (p<0.01) in C+D than R+D. The C+D group lost a significant (p<0.05) amount of LBW (51 to 47 kg). No decrease in LBW was observed in R+D. In addition, R+D had an increase (p<0.05) in RMR O2 ml/kg/min (2.6 to 3.1). The 24 hour RMR decreased (p<0.05) in the C+D group.

CONCLUSION

The addition of an intensive, high volume resistance training program resulted in preservation of LBW and RMR during weight loss with a VLCD.

Characteristics of successful and unsuccessful dieters: an application of signal detection methodology

Signal detection methods were used to identify predictors of successful weight loss in 177 mildly to moderately overweight women and men assigned to one of two weight-loss programs. Predictors included initial demographic, physiological, behavioral, and psychosocial characteristics, and program type (e.g. diet-only and diet-plus-exercise). Successful weight loss was defined as a loss of at least two units of body mass index at one year. Four subgroups were identified. Participants in the diet-plus-exercise program who were initially more satisfied with their bodies and did not have a history of repeated weight loss were most likely to succeed (63% succeeded). In contrast, participants assigned to the diet-plus-exercise program who were either extremely dissatisfied with their bodies or who had a history of repeated weight loss were at similar risk for failure as participants in the diet-only program (only 26% to 35% succeeded). The results underscore the potential utility of exploring these subgroups further to inform the development of new treatment strategies to increase the likelihood of success.

Low impact aerobic dance as a useful exercise mode for reducing body mass in mildly obese middle-aged women

The purpose of this study was to test the hypothesis that a low impact aerobic dance is a useful exercise mode for weight loss in obese middle-aged women. Sixty Japanese women, aged 50.9 +/- 6.7 years (initial %fat = 35.2 +/- 5.3%), participated in our 3-month weight-loss program consisting of diet and exercise prescription. To compare the effectiveness of exercise modes, the subjects were divided into the following two groups: aerobic dance group and jogging and/or cycling group. As a result, body mass (-3.1 and -3.3 kg respectively) and %fat (-6.1 and -5.3% respectively) significantly decreased (P < 0.05) in both groups, while fat-free mass remained essentially unchanged. Aerobic power such as maximal oxygen uptake and oxygen uptake corresponding to lactate threshold significantly increased (P < 0.05) in both groups. Significant difference in the alterations in these variables between groups could not be seen. The data of this study indicates that our weight-loss program with a low impact aerobic dance is as useful as jogging or cycling in improving body composition and aerobic power for mildly obese middle-aged women.

Cardiovascular effects of ephedrine, caffeine and yohimbine measured by thoracic electrical bioimpedance in obese women

Low caloric diet is a commonly accepted treatment in obesity. However, owing to moderate results, a pharmacological support has been proposed. As some efficacious drugs activate overall sympathetic activity, they might modify functions of the cardiovascular system. Three groups of subjects were studied: (1) nine obese women receiving only a standard hypocaloric diet; (2) nine obese women receiving a standard hypocaloric diet and ephedrine (2 x 25 mg) with caffeine (2 x 200 mg); (3) nine obese women receiving a standard hypocaloric diet and ephedrine (2 x 25 mg) with caffeine (2 x 200 mg) and yohimbine (2 x 5 mg). The cardiovascular state was evaluated by thoracic electrical bioimpedance, automatic sphygmomanometry and continuous ECG recording. In each patient, the haemodynamic study was performed twice: at rest, i.e. before treatment; and after 10 days of treatment. On the same days in each patient, the haemodynamic tests were performed during physical exercises (handgrip stress and cycloergometer exercise). Caffeine and ephedrine had no haemodynamic effect in resting patients. These two drugs led to an increase in ejection fraction during cycloergometer exercise. Addition of yohimbine increased diastolic pressure and heart rate but decreased ejection fraction and stroke index during rest. We also observed that addition of yohimbine decreased ejection fraction during the handgrip and cycloergometer exercise and increased cardiac load during dynamic exercise. Pharmacological supplement of ephedrine and caffeine to a low caloric diet modified the cardiovascular system weakly, but the addition of yohimbine to this regimen attenuated cardiac performance during rest and handgrip and increased cardiac work during dynamic exercise.

Development of questionnaires to measure psychosocial influences on children's physical activity

BACKGROUND

The purpose of this study was to develop and validate questionnaires used to measure psychosocial determinants of physical activity in preadolescent children.

METHODS

Three theory-based questionnaires and a measure of after-school physical activity were administered to 422 fifth-grade students. A cross-validation design was employed for psychometric development of the scales, including factor analysis, reliability, and validation by correlating scale scores with intention to be physically active and after-school physical activity.

RESULTS

The Social Influences scale contained a single factor. The Self-Efficacy scale contained three factors: support seeking, barriers, and positive alternatives. The Beliefs scale contained two factors: social outcomes and physical activity outcomes. Reliability coefficients ranged from about 0.50 to 0.78. Significant correlations were obtained between all six scales and intention in the development sample, and between five scales and intention in the validation sample. Significant correlations were obtained between social influence and self-efficacy barriers and physical activity in the development sample, and between social influences and physical activity in the validation sample.

CONCLUSIONS

Three scales to measure psychosocial determinants of physical activity were refined for use with rural, predominantly African-American, preadolescent children, and shown to be both reliable and valid. Factor analysis resulted in interpretable subscales that may be used as variables. These preliminary results provide support for using the scales to measure influences on activity in children.

The effects of exercise intensity on body composition, weight loss, and dietary composition in women

OBJECTIVE

There is controversy over whether exercise and/or exercise intensity has an effect on total caloric intake or diet composition. The purpose of this study was to test the effect of exercise intensity without dietary manipulation on body composition and/or weight loss and to determine whether exercise intensity affected total caloric intake or diet composition in normal weight young women.

METHODS

Fifteen women aged 18 to 34 years with a maximal oxygen consumption average or below on the Palo Alto norms served as subjects. Subjects were randomly assigned to: 1) low heart rate intensity exercise group (LI, N = 7) which exercised 40 to 45 minutes approximately four times weekly at a mean heart rate of 132 beats per minute (bpm); 2) high heart rate intensity group (HI, N = 8) which exercised 40 to 45 minutes approximately four times weekly at a mean HR of 163 bpm. All subjects were given a maximal exercise test prior to and during weeks eight, 12 and 16. The first 4 weeks served as a control period, followed by approximately 11 weeks of exercise. Each subject recorded her dietary intake for 1 complete week, including a weekend, during weeks 2, 6, 10 and 14 of the study.

RESULTS

VO2 max increased (p < .05) in HI (29 +/- 6 ml/kg/minute to 38 +/- 7) but did not change in LI (36 +/- 5 to 38 +/- 7). Percent fat decreased in HI (p < .05) (27 +/- 7 to 22 +/- 4) but was unchanged in LI (22 +/- 6 to 21 +/- 6). The weekly intake of total kcal, carbohydrate, protein and fat did change significantly for either group. The weekly intake of saturated fat declined significantly (p < .05) in HI (21.2 +/- 5.8 g to 14.9 +/- 5.5 g); their weekly intake of cholesterol also decreased (p < .05) between months 2 to 3 (249 +/- 109 mg to 159 +/- 58 mg). No other differences in dietary intake between groups were found.

CONCLUSION

High heart rate intensity exercise training without dietary manipulation resulted in a decrease in body fat, but not weight change, as well as a decrease in the intake of saturated fat and cholesterol in normal weight young women. These changes were not observed after low heart rate intensity training.

Exercise, occupational activity, and risk of endometrial cancer

We conducted a case-control study in western New York state among 232 women with newly-diagnosed endometrial cancer and 631 controls selected from the community. Physical activity was measured by participation in vigorous exercise and walking at four time periods: at age 16, and at 20, 10, and 2 years before the interview and by occupational activity based on a detailed lifetime history. Women who did a moderate amount of vigorous exercise at age 16 and at 20 years before the interview were at reduced risk as compared with those who reported no activity, with odds ratios (OR) (95% confidence intervals) of 0.51 (0.31-0.83) and 0.50 (0.29-0.89), respectively. However, there was no evidence of declining risk with greater amount of activity. At later times, 10 years and 2 years before the interview, being in the highest group with regard to vigorous activity was associated with a slightly but nor significant lower risk as compared with women who reported no activity; the adjusted OR were 0.72 (0.43-1.19) and 0.67 (0.42-1.09), respectively. Being in the highest category of miles walked at age 16 (i.e., > or = 15 miles per week) was associated with a slightly reduced risk as compared with not walking at all (OR 0.64 (0.26-1.16)), whereas the number of miles walked at other times was not related to reduced risk. Occupational physical activity was not related to the risk of endometrial cancer. Overall, these results indicate that physical activity at levels prevalent in this population has at most a modest relationship to reduced risk of endometrial cancer.

Exercise as treatment for obesity

In recent times, affluent societies have become less physically active, and this has undoubtedly contributed to the increased incidence of obesity. Formal programs of exercise training can reduce body weight and fat, but, in many cases, the changes produced by exercise are small. When combined with energy restriction, exercise results in little further weight loss, but there is a strong trend for a greater loss of body fat. Thus, during diet-induced weight loss, added exercise seems to accelerate fat loss and maintain lean body mass, a condition which may prevent a decline in RMR. It is becoming increasingly clear that weight loss is better maintained when exercise is part of a weight-reducing program. Furthermore, following a period of diet-induced weight loss, participation in regular exercise amounting to an energy expenditure of more than 1500 kcal/week will result in more successful maintenance of the lesser weight. An emphasis should be placed on adopting life-long habits conducive to weight control and overall health rather than temporary measures for weight loss. A program which encompasses regular physical activity, modest energy intake, and reduced calories from fat has the potential to meet such a goal. Regular physical activity has the potential to reverse insulin resistance, improve cardiovascular function and the blood lipid profile, and control high blood pressure. Overweight individuals can obtain these important benefits even if body weight is not completely normalized during a program of regular physical activity. This should help alleviate problems of diabetes, heart disease, and hypertension often associated with being overweight. Further research is needed to identify more specifically the optimal amount, type, and intensity of exercise needed to produce weight loss or maintain ideal body weight. To date, the best recommendation comes from the American College of Sports Medicine. Persons are urged to engage in regular physical activity which promotes a daily energy expenditure of at least 300 kcal/day and to choose from a variety of activities, in particular, those which are enjoyable and that can be continued for life.

Physical activity, nutrition, and chronic disease

Epidemiologic, animal, clinical, and metabolic studies demonstrate the independent roles of physical activity and nutrition in the prevention and treatment of several chronic diseases. Fewer data are available to describe the synergistic effects of exercise and diet, and questions remain as to whether and how these two lifestyle factors work together to promote health and prevent disease. This paper briefly reviews many of the known effects of physical activity and nutrition on the prevention and treatment of coronary heart disease, non-insulin-dependent diabetes mellitus, obesity, and osteoporosis as well as how exercise and diet may work together. A discussion of how to increase physical activity levels and how to improve dietary intake also is included. Finally, current exercise and dietary recommendations are summarized, as are directions for future research.

Contrasting effects of resistance and aerobic training on body composition and metabolism after diet-induced weight loss

This study examined whether exercise training facilitates maintenance of body weight at reduced levels following weight loss by attenuating weight loss-induced reductions in resting metabolism and fat oxidation. The effects of 12 weeks (three times per week) of either aerobic or weight training exercise on body weight, body composition, and energy metabolism during rest and following a meal in 18 older (mean +/- SE, 61 +/- 1 years; range, 56 to 70) subjects who had recently lost a mean of 9 +/- 1 kg were studied. During the exercise training period, the aerobic training group (five women, four men) had a significant (P < .05) reduction in body weight (-2.5 +/- 0.6 kg) as compared with the weight training group (five women, four men) (0.4 +/- 0.9 kg). Eight of nine aerobic training subjects lost additional weight, while six of nine weight training subjects gained weight. Neither type of training reversed the depressions in resting metabolism or fat oxidation rates (ie, resting or postprandial) that had occurred as a consequence of the prior weight loss. Thus, alterations in resting metabolism or fat oxidation (resting or postprandial) do not appear to be the mechanism(s) by which exercise training facilitates maintenance of diet-induced weight loss.

Aerobic fitness, blood lipids, and body fat in children

This study examined the association between aerobic fitness and serum cholesterol and the effects of controlling for gender, body composition, abdominal fat, and dietary saturated fat in 262 children. The 1-mile run was used to estimate fitness. Skinfolds were used in assessing body fat. Fit children had lower total cholesterol, low-density lipoprotein cholesterol, and triglyceride levels and higher high-density lipoprotein cholesterol levels than unfit children, except after adjustment for body fat and/or abdominal fat. Unfit children appear to be at an increased risk of unhealthy levels of serum cholesterol due primarily to increased levels of body fat.

Sustained weight reduction in moderately obese women results in decreased activity of skeletal muscle lipoprotein lipase

Obesity is an increasingly prevalent problem, and long-term maintenance of the weight-reduced state is difficult for the obese individual. Following weight reduction, many metabolic changes occur. Among these is an increase in adipose tissue lipoprotein lipase (ATLPL), which predicts an alteration in lipid fuel partitioning which may then contribute to resumption of the obese state. The purpose of this study was to test whether changes in skeletal muscle LPL (SMLPL) and its response to insulin/glucose after sustained weight reduction also indicate a potential altered partitioning of lipid fuels away from oxidative pathways in muscle to storage in adipose tissue. Biopsies of vastus lateralis muscle were carried out in premenopausal obese women (n = 11, 94 +/- 4 kg, mean +/- SEM) before and after consumption of a 900 kcal day-1 diet for 3 months followed by 3 months of isocaloric maintenance of the reduced weight (n = 11, 82 +/- 4 kg). SMLPL activity was measured in the fasted state and after 6 h insulin/glucose infusion, before and after sustained weight loss. SMLPL activities were also measured in six normal weight women. Fasting SMLPL activity in obese women (3.9 +/- 0.3 nmol FFA min-1 g-1) was similar to that measured in normal weight control women (4.4 +/- 0.5). Unlike normal weight controls in whom a 6 h insulin/glucose infusion decreased SMLPL activity, in obese women the response of SMLPL was positive (normal weight vs. obese: delta -0.8 +/- 0.3 vs. delta 1.6 +/- 0.5, P = 0.002). Following maintained weight reduction, fasting SMLPL in the obese group was reduced to 1.2 +/- 0.3 (obese before weight loss vs. obese after: P = 0.0001). This change in fasting SMLPL activity following weight loss/maintenance correlated with the resultant change in percent body fat (r s = 0.663, P = 0.026).(ABSTRACT TRUNCATED AT 250 WORDS)

Variables related to obesity and body fat: avenues to change

Obesity and overweight constitute major health concerns in this country today. This article provides a description of the terms overweight and obese, variables contributing to diet and exercise adherence, and practice implications for nurse practitioners.

The role of exercise in weight loss

Aerobic exercise has traditionally been viewed as a critical component of most weight-reduction programs. The resulting weight loss from the exercise alone, however, is often disappointing. Researchers too frequently fail to take into account the normal energy expenditure associated with living; the degree of obesity; the intensity and duration of the exercise itself; the activity during the recovery period; food intake before and after the exercise; and the age, gender, and training status of the individuals. Nor do they consider variations in baseline resting metabolic rates. In this article, the authors explore the effect of the intensity of aerobic exercise on weight loss, emphasizing the inability of many obese individuals to maintain an intensity level sufficient to produce significant weight loss. Aerobic exercise should be emphasized for its health benefits rather than as a short-term method of enhancing weight loss.