Indirect and direct relations between aerobic fitness, physical activity, and academic achievement in elementary school students

BACKGROUND

There is evidence to suggest that increasing physical activity (PA) improves academic achievement (AA) in children and that aerobic fitness is associated with both cognitive function and AA. However, it is not known how these variables are interrelated and analyses with adequate control for socioeconomic variables are needed. It was hypothesized that PA would not directly affect AA but would have an indirect effect on AA through its effect on aerobic fitness. The purpose of this study was to test this hypothesized mediation using path analysis.

METHODS

Cross-sectional data including AA, aerobic fitness, and daily PA assessed through accelerometry were collected from a large sample (N = 687) of 2nd and 3rd grade students. Demographic data were assessed via parent self-report.

RESULTS

A total of 401 students wore the accelerometer for at least 10 hours on 3 days or more and were included in the final path analysis to evaluate potential relations among PA (predictor), aerobic fitness (mediator), and WIAT-III subtest standard scores (outcomes; i.e., reading, spelling, and mathematics). Findings showed a direct effect of PA on aerobic fitness (b = 0.009, p < 0.001) and an indirect effect (mediation) of PA via fitness on math achievement (b = 0.003, p < 0.01) after controlling for student's grade, gender, body mass index, mother's education level, and household income, as well as intraclass correlations among classes and schools. Neither PA nor aerobic fitness were correlated with WIAT-III reading or spelling scores.

CONCLUSIONS

Mediation analysis indicated that PA exerted an influence on math achievement through its effects on aerobic fitness but was not associated with reading or spelling achievement scores.

Equivalent weight loss for weight management programs delivered by phone and clinic

OBJECTIVE

Face-to-face (FTF) weight management is costly and presents barriers for individuals seeking treatment; thus, alternate delivery systems are needed. The objective of this study was to compare weight management delivered by FTF clinic or group conference calls (phone).

DESIGN AND METHODS

Randomized equivalency trial in 295 overweight/obese men/women (BMI = 35.1±4.9, Age = 43.8±10.2, Minority = 39.8%). Weight loss (0-6 months) was achieved by reducing energy intake between 1,200 and 1,500 kcal/day and progressing physical activity (PA) to 300 min/week. Weight maintenance (7-18 months) provided adequate energy to maintain weight and continued 300 min/week of PA. Behavioral weight management strategies were delivered weekly for 6 months and gradually reduced during 7-18 months. A cost analysis provided a comparison of expenses between groups.

RESULTS

Weight change from baseline to 6 months was -13.4 ± 6.7% and -12.3 ± 7.0% for FTF clinic and phone, respectively. Weight change from 6-18 months was 6.4 ± 7.0% and 6.4 ± 5.2%, for FTF clinic and phone, respectively. The cost to FTF participants was $789.58 more per person.

CONCLUSIONS

Phone delivery provided equivalent weight loss and maintenance and reduced program cost. Ubiquitous access to phones provides a vast reach for this approach.

Weight management for individuals with intellectual and developmental disabilities: rationale and design for an 18 month randomized trial

Weight management for individuals with intellectual and developmental disabilities (IDD) has received limited attention. Studies on weight management in this population have been conducted over short time frames, in small samples with inadequate statistical power, infrequently used a randomized design, and have not evaluated the use of emerging effective dietary strategies such as pre-packaged meals (PMs). Low energy/fat PMs may be useful in individuals with IDD as they simplify meal planning, limit undesirable food choices, teach appropriate portion sizes, are convenient and easy to prepare, and when combined with fruits and vegetables provide a high volume, low energy dense meal. A randomized effectiveness trial will be conducted in 150 overweight/obese adults with mild to moderate IDD, and their study partners to compare weight loss (6 months) and weight maintenance (12 months) between 2 weight management approaches: 1. A Stop Light Diet enhanced with reduced energy/fat PMs (eSLD); and 2. A recommended care reduced energy/fat meal plan diet (RC). The primary aim is to compare weight loss (0-6 months) and weight maintenance (7-18 months) between the eSLD and RC diets. Secondarily, changes in chronic disease risk factors between the eSLD and RC diets including blood pressure, glucose, insulin, LDL-cholesterol, and HDL-cholesterol will be compared during both weight loss and weight maintenance. Finally, potential mediators of weight loss including energy intake, physical activity, data recording, adherence to the diet, study partner self-efficacy and daily stress related to dietary change will be explored.

Effects of growth hormone treatment in adults with Prader-Willi syndrome

OBJECTIVE

Since limited data exist on adults with Prader-Willi syndrome (PWS) and growth hormone (GH) treatment, we report our experience on the effects of treatment for one year on body composition, physical activity, strength and energy expenditure, diet, general chemistry and endocrine data with quality of life measures.

DESIGN

We studied 11 adults with PWS (6F:5M; average age=32 yrs) over a 2 year period with GH treatment during the first year only. Electrolytes, IGF-I, glucose, thyroid, insulin, lipids, body composition, physical activity and strength, diet, energy expenditure and quality of life data were collected and analyzed statistically using linear modeling at baseline, at 12 months following GH therapy and at 24 months after treatment cessation for 12 months.

RESULTS

Total lean muscle mass was significantly increased (p<0.05) during GH treatment along with moderate-vigorous physical activity and plasma IGF-I and HDL levels, but returned to near baseline after treatment. Percent body fat decreased during the 12 months of GH treatment but increased after treatment.

CONCLUSIONS

Previously reported beneficial effects of GH treatment in children with PWS were found in our adults regarding body composition, physical activity and plasma HDL and IGF-I levels. Several beneficial effects diminished to near baseline after cessation of GH treatment for 12 months supporting the continuation of treatment in PWS into adulthood and possibly adults not previously treated during childhood.

Improving weight maintenance using virtual reality (Second Life)

OBJECTIVE

Compare weight loss and maintenance between a face-to-face (FTF) weight management clinic and a clinic delivered via virtual reality (VR).

METHODS

Participants were randomized to 3 months of weight loss with a weekly clinic delivered via FTF or VR and then 6 months' weight maintenance delivered with VR. Data were collected at baseline and 3 and 6 months for weight and process variables. Twenty overweight and obese individuals (31.1 ± 3.6 years of age; body mass index, 32.8 ± 5.1; 85% females; 20% minorities) responded to advertisement and met inclusion criteria. Diets (1,200-1,800 kcal/d) used prepackaged meals, fruits and vegetables, and physical activity (300 min/wk).

RESULTS

Weight loss was significantly greater for FTF at 10.8% compared with 7.6% for VR (P < .05). However, weight maintenance was significantly greater for VR at 14.0% compared with 9.5% for FTF (P < .05).

CONCLUSIONS AND IMPLICATIONS

Virtual reality compares favorably with FTF for weight loss and may facilitate greater weight maintenance.

Aerobic exercise alone results in clinically significant weight loss for men and women: midwest exercise trial 2

Exercise is recommended by public health agencies for weight management; however, the role of exercise is generally considered secondary to energy restriction. Few studies exist that have verified completion of exercise, measured the energy expenditure of exercise, and prescribed exercise with equivalent energy expenditure across individuals and genders.

OBJECTIVE

The objective of this study was to evaluate aerobic exercise, without energy restriction, on weight loss in sedentary overweight and obese men and women.

DESIGN AND METHODS

This investigation was a randomized, controlled, efficacy trial in 141 overweight and obese participants (body mass index, 31.0 ± 4.6 kg/m(2) ; age 22.6 ± 3.9 years). Participants were randomized (2:2:1 ratio) to exercise at either 400 kcal/session or 600 kcal/session or to a nonexercise control. Exercise was supervised, 5 days/week, for 10 months. All participants were instructed to maintain usual ad libitum diets. Because of the efficacy design, completion of ≥90% of exercise sessions was an a priori definition of per protocol, and these participants were included in the analysis.

RESULTS

Weight loss from baseline to 10 months for the 400 and 600 kcal/session groups was 3.9 ± 4.9 kg (4.3%) and 5.2 ± 5.6 kg (5.7%), respectively, compared with weight gain for controls of 0.5 ± 3.5 kg (0.5%) (P < 0.05). Differences for weight loss from baseline to 10 months between the exercise groups and differences between men and women within groups were not statistically significant.

CONCLUSIONS

Supervised exercise, with equivalent energy expenditure, results in clinically significant weight loss with no significant difference between men and women.

Weight loss can lead to resolution of gastroesophageal reflux disease symptoms: a prospective intervention trial

OBJECTIVE

Weight gain is an important risk factor for gastroesophageal reflux disease (GERD); however, whether weight loss can lead to resolution of GERD symptoms is not clear. Our aim was to measure the impact of weight loss on GERD symptoms.

DESIGN AND METHODS

In a prospective cohort study at a tertiary referral center, overweight/obese subjects (BMI 25-39.9 kg/m2) were enrolled in a structured weight loss program. Weight loss strategies included dietary modifications, increased physical activity and behavioral changes. At baseline and at 6 months, BMI and waist circumference were measured and all participants completed a validated reflux disease questionnaire.

RESULTS

A total of 332 adult subjects, mean age 46 years and 66% women were prospectively enrolled. At baseline, the mean body weight, BMI, and waist circumference were 101 (±18) kg, 35 (±5) kg/m2 and 103 (±13) cm. At 6 months, majority of the subjects (97%) lost weight (average weight loss: 13 ± 7.7 kg) and as compared with baseline, there was a significant decrease in the overall prevalence of GERD (15 vs. 37%; P < 0.01) and the mean GERD symptom score (1.8 vs. 5.5; P < 0.01). Overall, 81% of the subjects had reduction in GERD symptom scores; 65% had complete resolution and 15% had partial resolution of reflux symptoms. There was a significant correlation between % body weight loss and reduction in GERD symptom scores (r = 0.17, P < 0.05).

CONCLUSIONS

In conclusion, the overall prevalence of GERD symptoms is high (37%) in overweight and obese subjects. A structured weight loss program can lead to complete resolution of GERD symptoms in the majority of these subjects.

One set resistance training: effect on body composition in overweight young adults

AIM

This study evaluate the impact of a 6-month, 1-set RT protocol on changes in weight and body composition in overweight young adults.

METHODS

Sixty-three overweight young adults were randomized to RT or control; 55 participants (RT: N.=32; C: N.=23; BMI=27.3+2.9; age=20.7+2.7 yrs) competed the 6 month training protocol and all assessments. RT consisted of 1-set, 9 exercises, 3 times/wk., with a resistance of 3-6 repetition maximum (RM). Body composition was assessed using dual energy X-ray absorptiometry, and strength using 1RM. Participants were instructed to maintain their normal ad libitum diet and normal activities of daily living.

RESULTS

Body weight and BMI increased significantly (P<0.05) in RT and C, however; the between group difference was not significant. RT induced a mean increase in fat-free mass of 1.5 kg in both males and females with significant between groups differences for change in fat-free mass noted in the total sample, and in both males and females. Between group differences for change in fat mass were not statistically significant in the total sample, or in either gender. Significant between group differences for change in % fat were noted in the total sample (RT=-0.3%, C=+5.8%, P<0.05) and in females (RT=-3.7%, C=+3.0%, P<0.01), but not in males (RT=3.4%, C=9.8%). Significant between group differences (P<0.001) were observed for change in chest (RT=45 %, C=3%) and leg press (RT=57 %, C=9%) maximal strength.

CONCLUSION

A 6 month, 1-set RT program in overweight young adults increased fat-free mass and prevented increases in fat mass and % fat.

Resistance training volume, energy balance and weight management: rationale and design of a 9 month trial

The increased prevalence of obesity and the lack of treatment success both argue for the design and evaluation of strategies to prevent the development of overweight and obesity. To date, the role of resistance training (RT) in this regard is largely unexplored. RT may be effective for weight management as a result of increased fat-free mass (FFM), which may result in increased resting metabolic rate and increased physical activity energy expenditure. However, the literature relative to the efficacy of RT protocols recommended for healthy adults to alter the aforementioned parameters is inconsistent or inadequately evaluated. We will conduct a 9 month randomized controlled efficacy trial to compare changes in body composition (fat mass, FFM, % body fat) and energy balance in response to 2 volumes of RT (1 vs. 3 sets vs. non-exercise control) both at the completion of training (9 months) and 1 year later (body composition). This investigation will be conducted in a sample of healthy, normal and overweight, sedentary, young adult men and women; a group at high risk for development of overweight and obesity. Our results will provide information relative to the minimum volume of RT that may be associated with body weight/fat gain which may inform the development of guidelines for RT to prevent weight gain or to alter body composition.

The role of physical activity in pediatric obesity

This article provides an overview of the benefits of physical activity in children, including the effects on obesity, cognitive development, academic achievement and cognition, and health. The recommendations of health organizations are also outlined, and practical recommendations are provided for parents and educators.

Reliability of peak treadmill exercise tests in mild Alzheimer disease

INTRODUCTION

The purpose of this study was to determine the reliability of treadmill peak exercise testing in people with very mild-to-mild Alzheimer disease (AD).

METHODS

Sixteen subjects with very mild-to-mild AD performed graded peak treadmill exercise tests twice within a 14-day period. Heart rate, oxygen consumption, and respiratory exchange ratio (RER) were continuously monitored. Peak values were analyzed for absolute level of agreement.

RESULTS

Fourteen participants (87.5%) completed testing. Reliability was excellent with total peak oxygen consumption (VO2peak) (ml/kg/min) highly correlated across the two tests (r = 0.94, p < .001) with an intraclass correlation coefficient (ICC[3,1]) of 0.92 (95% confidence interval (CI) = 0.78, 0.97). The standard error of measurement (SEM) for VO2peak was 1.29 (95% CI = 0.88, 1.89).

CONCLUSIONS

These results indicate that peak exercise testing on a treadmill is reliable in the early stages of AD.

Classroom-based physical activity, cognition, and academic achievement

BACKGROUND

There is increasing evidence for the association between physical activity, cardiovascular fitness, fatness, and cognitive function during childhood and adolescence. Evidence also suggests that these variables are linked to academic achievement. Classroom-based physical activity provides a viable approach to improve fitness, body mass index (BMI), cognitive function, and ultimately academic achievement.

METHODS

Studies examining the relation between physical activity, fitness, fatness, cognitive function, and academic achievement are described. The results of a large-scale, longitudinal, cluster randomized trial to examine the impact of classroom based physical activity on body mass index and academic achievement will be presented.

RESULTS

Overall, the data support the link between physical activity, cognitive function, and academic achievement. The role of physical activity in the classroom was also supported by the Physical Activity Across the Curriculum (PAAC) project. Physically active academic lessons of moderate intensity improved overall performance on a standardized test of academic achievement by 6% compared to a decrease of 1% for controls (p<0.02). Body mass index increased less from baseline to 3 years in students with greater than 75 minutes of PAAC lessons per week (1.8 BMI) compared to students with less than 75 minutes of PAAC per week (2.4 BMI), p<0.00.

CONCLUSIONS

Future research examining the effects of physically active academic instruction is warranted. The impact of physically active academic lessons of greater intensity may provide larger benefits for body mass index and academic achievement.

Evaluation of an approach to weight loss in adults with intellectual or developmental disabilities

Of 79 overweight adults with intellectual or developmental disabilities who participated in a weight loss intervention, 73 completed the 6-month diet phase. The emphasis in the intervention was consumption of high volume, low calorie foods and beverages, including meal-replacement shakes. Lower calorie frozen entrees were recommended to control portion size. A walking activity was encouraged. Participants attended monthly meetings in which a small amount of cash was exchanged for self-recorded intake and exercise records completed on picture-based forms. Average weight loss was 13.2 pounds (6.3%) of baseline weight at 6 months, with weight loss shown by 64 of the 73 individuals enrolled. Those completing a 6-month follow-up phase showed weight loss of 9.4% of baseline. Increased choice and control are discussed as possible contributors to individual success.

Weight loss-induced alterations in serum markers of bone turnover persist during weight maintenance in obese men and women

OBJECTIVE

Moderate weight loss alters bone turnover and reduces bone mineral density in overweight men and women. However, it is not known whether bone turnover is normalized during weight maintenance postweight loss. Thus, the objective of the present study was to examine changes in serum bone turnover markers during 9 months of weight maintenance following weight reduction on a very low-energy diet (VLED) in obese men and women.

METHODS

Thirty-seven men (n = 13) and women (n = 24) aged 50 +/- 9.8 years underwent 3 months of weight reduction on a VLED ( approximately 500 kcal/d) followed by 9 months on either a low-carbohydrate or low-fat weight maintenance diet ( approximately 1600 kcal/d). Concentrations of osteocalcin (OC) and C-terminal peptide of type I collagen (CTX) in serum were measured using enzyme-linked immunosorbent assay at baseline and at months 3, 6, and 12. Serum parathyroid (PTH) concentrations were measured using a chemiluminescent immunoassay at all 4 time points. Data were analyzed using a 3-factor-repeated measures analysis of variance.

RESULTS

Average weight loss was 19% +/- 3% and, during the 9-month weight maintenance period, average weight gain was approximately 3%, with no differences due to diet composition. Serum concentrations of OC and CTX significantly increased after weight reduction and remained elevated during weight maintenance. Serum PTH was reduced after weight loss. Percent changes in OC and CTX were correlated during weight maintenance (r = -0.437, p = 0.008), but not during weight loss. Percent changes in CTX and body weight were negatively correlated during weight loss (r = -0.474, p = 0.003) and maintenance (r = -0.455, p = 0.006).

CONCLUSIONS

Weight loss induced via a VLED may result in an imbalance between bone formation and resorption and accelerate remodeling. The deleterious effect of energy restriction on bone remodeling rate appears to persist during weight maintenance.

Comparison of a reduced carbohydrate and reduced fat diet for LDL, HDL, and VLDL subclasses during 9-months of weight maintenance subsequent to weight loss

OBJECTIVES

This study compared LDL, HDL, and VLDL subclasses in overweight or obese adults consuming either a reduced carbohydrate (RC) or reduced fat (RF) weight maintenance diet for 9 months following significant weight loss.

METHODS

Thirty-five (21 RC; 14 RF) overweight or obese middle-aged adults completed a 1-year weight management clinic. Participants met weekly for the first six months and bi-weekly thereafter. Meetings included instruction for diet, physical activity, and behavior change related to weight management. Additionally, participants followed a liquid very low-energy diet of approximately 2092 kJ per day for the first three months of the study. Subsequently, participants followed a dietary plan for nine months that targeted a reduced percentage of carbohydrate (approximately 20%) or fat (approximately 30%) intake and an energy intake level calculated to maintain weight loss. Lipid subclasses using NMR spectroscopy were analyzed prior to weight loss and at multiple intervals during weight maintenance.

RESULTS

Body weight change was not significantly different within or between groups during weight maintenance (p>0.05). The RC group showed significant increases in mean LDL size, large LDL, total HDL, large and small HDL, mean VLDL size, and large VLDL during weight maintenance while the RF group showed increases in total HDL, large and small HDL, total VLDL, and large, medium, and small VLDL (p<0.05). Group*time interactions were significant for large and medium VLDL (p>0.05).

CONCLUSION

Some individual lipid subclasses improved in both dietary groups. Large and medium VLDL subclasses increased to a greater extent across weight maintenance in the RF group.

Construct validity of a continuous metabolic syndrome score in children

OBJECTIVE

The primary purpose of this study was to examine the construct validity of a continuous metabolic syndrome score (cMetS) in children. The secondary purpose was to identify a cutpoint value(s) for an adverse cMetS based on receiver operating characteristic (ROC) curve analysis.

METHODS

378 children aged 7 to 9 years were assessed for the metabolic syndrome which was determined by age-modified cutpoints. High-density-lipoprotein cholesterol, triglycerides, the homeostasis assessment model of insulin resistance, mean arterial pressure, and waist circumference were used to create a cMetS for each subject.

RESULTS

About half of the subjects did not possess any risk factors while about 5% possessed the metabolic syndrome. There was a graded relationship between the cMetS and the number of adverse risk factors. The cMetS was lowest in the group with no adverse risk factors (-1.59 +/- 1.76) and highest in those possessing the metabolic syndrome (> or =3 risk factors) (7.05 +/- 2.73). The cutoff level yielding the maximal sensitivity and specificity for predicting the presence of the metabolic syndrome was a cMetS of 3.72 (sensitivity = 100%, specificity = 93.9%, and the area of the curve = 0.978 (0.957-0.990, 95% confidence intervals).

CONCLUSION

The results demonstrate the construct validity for the cMetS in children. Since there are several drawbacks to identifying a single cut-point value for the cMetS based on this sample, we urge researchers to use the approach herein to validate and create a cMetS that is specific to their study population.

Total body bone mineral content and density during weight loss and maintenance on a low- or recommended-dairy weight-maintenance diet in obese men and women

BACKGROUND

Diets high in either dairy or calcium during moderate weight reduction both prevent loss of bone mineral density (BMD) and suppress bone turnover. The purpose of this study was to determine whether recommended dairy and calcium intakes during weight maintenance favorably affect total body BMD (TBBMD) and bone mineral content (TBBMC) in obese adults.

METHODS

Obese men (n=49) and women (n=64), aged 40.8+/-0.6 years, underwent 12 weeks of moderate energy restriction (approximately 1200 kcal/day) followed by 24 weeks on either a low or recommended dairy weight maintenance diet. The TBBMC and TBBMD values were measured using dual energy X-ray absorptiometry at baseline, 12, 24 and 36 weeks. Concentrations of calcium, intact parathyroid hormone (iPTH), 25OH and 1,25 (OH)(2) vitamin D in plasma were also measured. Data were analyzed using a two-factor repeated measures analysis of variance.

RESULTS

After weight loss, women exhibited a small, but statistically significant, increase in TBBMC (1.17+/-0.57%), whereas TBBMD increased in the men (1.34+/-0.28%). The iPTH concentration decreased significantly in all subjects. Despite significantly greater intakes of calcium, vitamin D and protein compared with the recommended dairy diet, there were no treatment-related differences in outcome variables after 24 weeks of weight maintenance. The TBBMC remained unchanged in women during weight stabilization; both TBBMC and TBBMD decreased in men (-1.59+/-0.51% and -0.70+/-0.25%, respectively).

CONCLUSIONS

In summary, results of this study do not provide convincing evidence that moderate weight loss through energy restriction and mild exercise reduces TBBMC in obese men and women. Similarly, a weight-maintenance diet providing the recommended daily servings of dairy does not seem to affect changes in BMC after weight loss.

Group versus individual phone-based obesity treatment for rural women

Rural women have among the highest rates of obesity and sedentary lifestyle, yet few studies have examined strategies for delivering state-of-the-art obesity treatment to hard-to-reach rural areas. The purpose of this pilot trial was to examine the impact and cost-effectiveness of a 6-month behavioral weight loss program delivered to rural women by phone either one-on-one with a counselor or to a group via conference call. Thirty-four rural women (mean BMI=34.4, SD=4.6) were randomized to group phone-based treatment or individual phone-based treatment. Completers analysis showed that weight loss was greater in the group condition (mean=14.9 kg=, SD=4.4) compared to the individual condition (mean=9.5 kg, SD=5.2; p=.03). Among the total sample, 62% of participants in the group condition achieved the 10% weight loss goal compared to 50% in the individual condition, and group treatment was found to be more cost-effective. Future research is warranted to examine the benefits of group phone-based treatment for long-term management of obesity among rural populations.

Minimal resistance training improves daily energy expenditure and fat oxidation

Long-term resistance training (RT) may result in a chronic increase in 24-h energy expenditure (EE) and fat oxidation to a level sufficient to assist in maintaining energy balance and preventing weight gain. However, the impact of a minimal RT program on these parameters in an overweight college-aged population, a group at high risk for developing obesity, is unknown.

PURPOSE

We aimed to evaluate the effect of 6 months of supervised minimal RT in previously sedentary, overweight (mean +/- SEM, BMI = 27.7 +/- 0.5 kg x m(-2)) young adults (21.0 +/- 0.5 yr) on 24-h EE, resting metabolic rate (RMR), sleep metabolic rate (SMR), and substrate oxidation using whole-room indirect calorimetry 72 h after the last RT session.

METHODS

Participants were randomized to RT (one set, 3 d x wk(-1), three to six repetition maximums, nine exercises; N = 22) or control (C, N = 17) groups and completed all assessments at baseline and at 6 months.

RESULTS

There was a significant (P < 0.05) increase in 24-h EE in the RT (527 +/- 220 kJ x d(-1)) and C (270 +/- 168 kJ x d(-1)) groups; however, the difference between groups was not significant (P = 0.30). Twenty-four hours of fat oxidation (g x d(-1)) was not altered after RT; however, reductions in RT assessed during both rest (P < 0.05) and sleep (P < 0.05) suggested increased fat oxidation in RT compared with C during these periods. SMR (8.4 +/- 8.6%) and RMR (7.4 +/- 8.7%) increased significantly in RT (P < 0.001) but not in C, resulting in significant (P < 0.001) between-group differences for SMR with a trend for significant (P = 0.07) between-group differences for RMR.

CONCLUSION

A minimal RT program that required little time to complete (11min per session) resulted in a chronic increase in energy expenditure. This adaptation in energy expenditure may have a favorable impact on energy balance and fat oxidation sufficient to assist with the prevention of obesity in sedentary, overweight young adults, a group at high risk for developing obesity.

American College of Sports Medicine Position Stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults

Overweight and obesity affects more than 66% of the adult population and is associated with a variety of chronic diseases. Weight reduction reduces health risks associated with chronic diseases and is therefore encouraged by major health agencies. Guidelines of the National Heart, Lung, and Blood Institute (NHLBI) encourage a 10% reduction in weight, although considerable literature indicates reduction in health risk with 3% to 5% reduction in weight. Physical activity (PA) is recommended as a component of weight management for prevention of weight gain, for weight loss, and for prevention of weight regain after weight loss. In 2001, the American College of Sports Medicine (ACSM) published a Position Stand that recommended a minimum of 150 min wk(-1) of moderate-intensity PA for overweight and obese adults to improve health; however, 200-300 min wk(-1) was recommended for long-term weight loss. More recent evidence has supported this recommendation and has indicated more PA may be necessary to prevent weight regain after weight loss. To this end, we have reexamined the evidence from 1999 to determine whether there is a level at which PA is effective for prevention of weight gain, for weight loss, and prevention of weight regain. Evidence supports moderate-intensity PA between 150 and 250 min wk(-1) to be effective to prevent weight gain. Moderate-intensity PA between 150 and 250 min wk(-1) will provide only modest weight loss. Greater amounts of PA (>250 min wk(-1)) have been associated with clinically significant weight loss. Moderate-intensity PA between 150 and 250 min wk(-1) will improve weight loss in studies that use moderate diet restriction but not severe diet restriction. Cross-sectional and prospective studies indicate that after weight loss, weight maintenance is improved with PA >250 min wk(-1). However, no evidence from well-designed randomized controlled trials exists to judge the effectiveness of PA for prevention of weight regain after weight loss. Resistance training does not enhance weight loss but may increase fat-free mass and increase loss of fat mass and is associated with reductions in health risk. Existing evidence indicates that endurance PA or resistance training without weight loss improves health risk. There is inadequate evidence to determine whether PA prevents or attenuates detrimental changes in chronic disease risk during weight gain.

Energy expenditure of the physical activity across the curriculum intervention

Physical activity is frequently a component of interventions designed to diminish weight gain in children. It is essential to determine whether the energy expenditure (EE) elicited by these interventions is sufficient to reduce the rate of weight gain.

PURPOSE

To quantify the EE of the Physical Activity across the Curriculum (PAAC) intervention. This intervention involved two 10-min physically active academic lessons per day, taught by classroom teachers.

METHODS

We assessed EE of PAAC in 19 males and 19 females using both an indirect calorimeter (IC) (COSMED K4b(2)) and an accelerometer (ActiGraph) (AC). Independent t-tests were used to evaluate gender differences. Dependent t-tests were used to examine the difference between EE assessed by IC and AC. The agreement between EE measured by IC and estimated by AC was evaluated using a Bland-Altman plot. A Pearson correlation between EE measured by IC and estimated by AC was calculated.

RESULTS

There were no significant gender differences for age, BMI, or EE; therefore, analyses by gender were not performed. The mean EE measured by IC was 3.1 +/- 1.0 kcal x min(-1) (3.4 METs). Mean EE estimated by AC (1.8 +/- 0.9 kcal x min(-1)) was significantly lower (P < 0.05) than EE measured by IC (mean underestimation = 1.3 kcal x min(-1)). The Bland-Altman plot suggested increased underestimation with increased levels of EE. The 95% limits of agreement were large (-2.8 to +0.3 kcal x min(-1)). The correlation between EE measured by IC and estimated by AC was r = 0.68 (P < 0.001).

CONCLUSION

PAAC elicited a level of EE that may prevent excessive weight gain in children. AC significantly underestimated the EE of PAAC lessons and may not provide useful EE estimates in this context.

Effects of dairy intake on weight maintenance

BACKGROUND

To compare the effects of low versus recommended levels of dairy intake on weight maintenance and body composition subsequent to weight loss.

DESIGN AND METHODS

Two site (University of Kansas-KU; University of Tennessee-UT), 9 month, randomized trial. Weight loss was baseline to 3 months, weight maintenance was 4 to 9 months. Participants were maintained randomly assigned to low dairy (< 1 dairy serving/d) or recommended dairy (> 3 servings/d) diets for the maintenance phase. Three hundred thirty eight men and women, age: 40.3 +/- 7.0 years and BMI: 34.5 +/- 3.1, were randomized; Change in weight and body composition (total fat, trunk fat) from 4 to 9 months were the primary outcomes. Blood chemistry, blood pressure, resting metabolism, and respiratory quotient were secondary outcomes. Energy intake, calcium intake, dairy intake, and physical activity were measured as process evaluation.

RESULTS

During weight maintenance, there were no overall significant differences for weight or body composition between the low and recommended dairy groups. A significant site interaction occurred with the low dairy group at KU maintaining weight and body composition and the low dairy group at UT increasing weight and body fat. The recommended dairy group exhibited reductions in plasma 1,25-(OH)2-D while no change was observed in the low dairy group. No other differences were found for blood chemistry, blood pressure or physical activity between low and recommended dairy groups. The recommended dairy group showed significantly greater energy intake and lower respiratory quotient compared to the low dairy group.

CONCLUSION

Weight maintenance was similar for low and recommended dairy groups. The recommended dairy group exhibited evidence of greater fat oxidation and was able to consume greater energy without greater weight gain compared to the low dairy group. Recommended levels of dairy products may be used during weight maintenance without contributing to weight gain compared to diets low in dairy products.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00686426.

Cardiorespiratory fitness and brain atrophy in early Alzheimer disease

OBJECTIVE

To examine the correlation of cardiorespiratory fitness with brain atrophy and cognition in early-stage Alzheimer disease (AD).

BACKGROUND

In normal aging physical fitness appears to mitigate functional and structural age-related brain changes. Whether this is observed in AD is not known.

METHODS

Subjects without dementia (n = 64) and subjects with early-stage AD (n = 57) had MRI and standard clinical and psychometric evaluations. Peak oxygen consumption (VO(2)(peak)), the standard measure of cardiorespiratory fitness, was assessed during a graded treadmill test. Normalized whole brain volume, a brain atrophy estimate, was determined by MRI. Pearson correlation and linear regression were used to assess fitness in relation to brain volume and cognitive performance.

RESULTS

Cardiorespiratory fitness (VO(2)(peak)) was modestly reduced in subjects with AD (34.7 [5.0] mL/kg/min) vs subjects without dementia (38.1 [6.3] mL/kg/min, p = 0.002). In early AD, VO(2)(peak) was associated with whole brain volume (beta = 0.35, p = 0.02) and white matter volume (beta = 0.35, p = 0.04) after controlling for age. Controlling for additional covariates of sex, dementia severity, physical activity, and physical frailty did not attenuate the relationships. VO(2)(peak) was associated with performance on delayed memory and digit symbol in early AD but not after controlling for age. In participants with no dementia, there was no relationship between fitness and brain atrophy. Fitness in participants with no dementia was associated with better global cognitive performance (r = 0.30, p = 0.02) and performance on Trailmaking A and B, Stroop, and delayed logical memory but not after controlling for age.

CONCLUSIONS

Increased cardiorespiratory fitness is associated with reduced brain atrophy in Alzheimer disease (AD). Cardiorespiratory fitness may moderate AD-related brain atrophy or a common underlying AD-related process may impact both brain atrophy and cardiorespiratory fitness.

Physical activity across the curriculum: year one process evaluation results

BACKGROUND

Physical Activity Across the Curriculum (PAAC) is a 3-year elementary school-based intervention to determine if increased amounts of moderate intensity physical activity performed in the classroom will diminish gains in body mass index (BMI). It is a cluster-randomized, controlled trial, involving 4905 children (2505 intervention, 2400 control).

METHODS

We collected both qualitative and quantitative process evaluation data from 24 schools (14 intervention and 10 control), which included tracking teacher training issues, challenges and barriers to effective implementation of PAAC lessons, initial and continual use of program specified activities, and potential competing factors, which might contaminate or lessen program effects.

RESULTS

Overall teacher attendance at training sessions showed exceptional reach. Teachers incorporated active lessons on most days, resulting in significantly greater student physical activity levels compared to controls (p < 0.0001). Enjoyment ratings for classroom-based lessons were also higher for intervention students. Competing factors, which might influence program results, were not carried out at intervention or control schools or were judged to be minimal.

CONCLUSION

In the first year of the PAAC intervention, process evaluation results were instrumental in identifying successes and challenges faced by teachers when trying to modify existing academic lessons to incorporate physical activity.

Sex difference in the association of the angiotensin converting enzyme I/D polymorphism and body mass index

BACKGROUND

Angiotensin converting enzyme (ACE) catayzes the formation of angiotensin I to angiotensin II. A polymorphism has been identified in intron 16 in which a 287 base-pair alu sequence was found to be present (insertion or I) or absent (deletion or D) in the population. ACE and the components of the renin-angiotensin system are expressed in adipose tissue and therefore the I/D polymorphism within ACE may be associated with obesity.

MATERIAL/METHODS

This study involved genotyping two groups with differing body mass indexes (BMI <or=25 and BMI >or=30) that were composed primarily of middle-age Caucasian subjects (n=421).

RESULTS

The male groups differed significantly in allele frequency at the ACE locus with the I allele more frequent in the BMI >or=30 group (p<0.05). While the female BMI >or=30 group also had a higher I allele frequency than the BMI <or=25 group, the difference is not significant.

CONCLUSIONS

Our results demonstrate a sex difference in the association of the I/D polymorphism and BMI. Our findings differ from some other previous studies using various population groups which indicate that the ACE I/D polymorphism may be differentially associated with obesity depending on multiple factors.

Health behaviors and weight status among urban and rural children

INTRODUCTION

Pediatric overweight is currently reaching epidemic proportions but little information exists on differences in weight related behaviors between urban and rural children.

OBJECTIVE

To assess health behaviors and weight status among urban and rural school-age children.

METHODS

Fifth-grade children at two urban and two rural schools were invited to participate in an assessment study of their health behaviors and weight status. A total of 138 children (mean age = 10 years; % female = 54.6) chose to participate.

RESULTS

Children in rural and urban areas consumed equivalent calories per day and calories from fat, but rural children ate more junk food and urban children were more likely to skip breakfast. Urban children engaged in more metabolic equivalent tasks and had slightly higher total sedentary activity than rural children. The BMI percentile was equivalent across rural and urban children but rural children were more often overweight and urban children were more often at risk for overweight.

CONCLUSIONS

Although some variables were equivalent across urban and rural children, results indicate some key health behavior differences between groups. Results should be interpreted with caution as the sample size was small and there were demographic differences between urban and rural samples.

Alteration of dietary fat intake to prevent weight gain: Jayhawk Observed Eating Trial

OBJECTIVE

To examine the effects of ad libitum diets with three distinct levels of fat intake for the prevention of weight gain in sedentary, normal-weight and overweight men and women.

METHODS AND PROCEDURES

Three hundred and five participants were randomized to one of three diets. The diets targeted <25% of energy from fat (low fat (LF)), between 28 and 32% of energy from fat (moderate fat (MF)), or >35% of energy from fat (high fat (HF)). Participants consumed two meals per day on weekdays and one meal per day on weekends in a university cafeteria over a 12-week period. Energy and nutrient content of cafeteria foods were measured by digital photography. All meals and snacks consumed outside the cafeteria were measured by dietary recall. All analysis of energy and nutrient content was completed using Nutrition Data System for Research (NDS-R) version 2005.

RESULTS

Two hundred and sixty participants completed the study. LF gained 0.1 +/- 3.1 kg, MF gained 0.8 +/- 2.5 kg, and HF gained 1.0 +/- 2.2 kg and there was no gender or age effect. Longitudinal mixed modeling indicated a significant difference among the groups in weight over time (P = 0.0366). When adjusting for total energy intake, which was a significant predictor of weight over time, the global effect for the group was eliminated. Thus, increasing weight was a function of increasing energy but not increasing percentage of fat intake.

DISCUSSION

Energy intake, but not percentage of energy from fat, appears responsible for the observed weight gain. LF diets may contribute to weight maintenance and HF diets may promote weight gain due to the influence of fat intake on total energy intake.

Physical activity across the curriculum (PAAC): Rationale and design

BACKGROUND

Over the years schools have reduced physical education and recess time in favor of more academic instruction. Due to the drastic rise in obesity levels among children, some states have begun to mandate minimum amounts of physical activity (PA) that school children receive, causing schools to find alternative methods for increasing PA levels. Physical Activity Across the Curriculum (PAAC) is a 3-year randomized clinical trial incorporating moderate-intensity PA in elementary schools to reduce childhood obesity. This paper describes the rational, design, and methods of the PAAC intervention study.

METHODS

Twenty-two elementary schools were randomized to either a control or intervention condition. In schools randomized to the intervention condition (PAAC), regular classroom teachers were taught how to incorporate PA into standard academic lessons. Teachers were asked to accumulate 90-100 min/week of PAAC each week through out the 3-year study period. Schools randomized to the control group did not alter their teaching methods. Direct observation of PA levels in the classroom was collected weekly. Height and weight was measured twice a year to calculate BMI.

RESULTS

Two years of the intervention have been completed and only one school has left the study. The remaining 21 schools are participating in the final intervention year.

CONCLUSIONS

The results from the PAAC intervention may provide schools with an alternative method to increase PA levels in children and reduce childhood obesity.

Aerobic fitness attenuates the metabolic syndrome score in normal-weight, at-risk-for-overweight, and overweight children

OBJECTIVE

The purpose of this study was to examine the combined influence of aerobic fitness and BMI on the metabolic syndrome score in children.

METHODS

A total of 375 children (193 girls and 182 boys) aged 7 to 9 years were categorized as being normal weight, at risk for overweight, and overweight on the basis of BMI and aerobic fitness (high or low based on median split) via a submaximal physical working capacity test. Participants were cross-tabulated into 6 BMI fitness categories. High-density lipoprotein cholesterol and triglyceride levels, homeostasis assessment model of insulin resistance, mean arterial pressure, and waist circumference were used to create a continuous metabolic syndrome score.

RESULTS

Both BMI and fitness were associated with the metabolic syndrome score. In general, the metabolic syndrome score increased across the cross-tabulated groups with the normal-weight, high-fit group possessing the lowest metabolic syndrome score and the overweight, unfit group possessing the highest metabolic syndrome score. Children who were at risk for overweight and had high fitness had a lower metabolic syndrome score compared with those at-risk-for-overweight, less-fit children, and the score was similar to that of the less-fit, normal-weight children. Furthermore, a high fitness level resulted in a lower metabolic syndrome score in overweight children compared with overweight children with low fitness.

CONCLUSIONS

High fitness levels modified the impact that BMI had on the metabolic syndrome score in children. Increasing a child's fitness level could be one method for reducing the risk of obesity-related comorbidities.

Comparison of a low carbohydrate and low fat diet for weight maintenance in overweight or obese adults enrolled in a clinical weight management program

Background

Recent evidence suggests that a low carbohydrate (LC) diet may be equally or more effective for short-term weight loss than a traditional low fat (LF) diet; however, less is known about how they compare for weight maintenance. The purpose of this study was to compare body weight (BW) for participants in a clinical weight management program, consuming a LC or LF weight maintenance diet for 6 months following weight loss.

Methods

Fifty-five (29 low carbohydrate diet; 26 low fat diet) overweight/obese middle-aged adults completed a 9 month weight management program that included instruction for behavior, physical activity (PA), and nutrition. For 3 months all participants consumed an identical liquid diet (2177 kJ/day) followed by 1 month of re-feeding with solid foods either low in carbohydrate or low in fat. For the remaining 5 months, participants were prescribed a meal plan low in dietary carbohydrate (~20%) or fat (~30%). BW and carbohydrate or fat grams were collected at each group meeting. Energy and macronutrient intake were assessed at baseline, 3, 6, and 9 months.

Results

The LC group increased BW from 89.2 ± 14.4 kg at 3 months to 89.3 ± 16.1 kg at 9 months (P = 0.84). The LF group decreased BW from 86.3 ± 12.0 kg at 3 months to 86.0 ± 14.0 kg at 9 months (P = 0.96). BW was not different between groups during weight maintenance (P = 0.87). Fifty-five percent (16/29) and 50% (13/26) of participants for the LC and LF groups, respectively, continued to decrease their body weight during weight maintenance.

Conclusion

Following a 3 month liquid diet, the LC and LF diet groups were equally effective for BW maintenance over 6 months; however, there was significant variation in weight change within each group.

Peripheral insulin and brain structure in early Alzheimer disease

OBJECTIVE

Accumulating evidence suggests insulin and insulin signaling may be involved in the pathophysiology of Alzheimer disease (AD). The relationship between insulin-mediated glucoregulation and brain structure has not been assessed in individuals with AD.

METHODS

Nondemented (Clinical Dementia Rating [CDR] 0, n = 31) and early stage AD (CDR 0.5 and 1, n = 31) participants aged 65 years and older had brain MRI to determine whole brain and hippocampal volume and 3-hour IV glucose tolerance tests to determine glucose and insulin area under the curve (AUC). Linear regression models were used to assess the relationship of insulin and glucose with brain volume, cognition, and dementia severity.

RESULTS

In early AD, insulin and glucose AUCs were related to whole brain (insulin beta = 0.66, p < 0.001; glucose beta = 0.45, p < 0.01) and hippocampal volume (insulin beta = 0.42, p < 0.05; glucose beta = 0.46, p < 0.05). These relationships were independent of age, sex, body mass index, body fat, cardiorespiratory fitness, physical activity, cholesterol, and triglycerides. Insulin AUC, but not glucose, was associated with cognitive performance in early AD (beta = 0.40, p = 0.04). Insulin AUC was associated with dementia severity (Pearson r = -0.40, p = 0.03). Glucose and insulin were not related to brain volume or cognitive performance in nondemented individuals.

CONCLUSIONS

Increased peripheral insulin is associated with reduced Alzheimer disease (AD)-related brain atrophy, cognitive dysfunction, and dementia severity, suggesting that insulin signaling may play a role in the pathophysiology of AD.

Effects of long-term aerobic exercise on EPOC

This study sought to determine the influence of 16 months of progressive aerobic exercise on excess postexercise oxygen consumption (EPOC) and the extent EPOC contributed to weight management. Twenty-five overweight/obese women and 16 overweight/obese men participated in a 16-month exercise program (moderate-intensity treadmill walking) that progressed across the first 26 weeks to 5 days.wk(-1), 45 min.session(-1), and 75% HRR. Three-hour EPOC was measured at baseline, 9 months, and 16 months by indirect calorimetry in response to an exercise session (treadmill walking), in which energy expenditure (EE) was estimated from the participant's previous 10 exercise sessions. For women, EPOC was 7.5 +/- 4.9, 9.6 +/- 7.6, and 6.5 +/- 6.5 L at baseline, 9 months, and 16 months, respectively (p > 0.05). For men, EPOC increased from baseline (11.8 +/- 6.8 L) to 9 months (13.5 +/- 8.6 L) (p < 0.05) with no further increase at 16 months (13.5 +/- 11.0 L). Change in EPOC was correlated with change in EE at 9 months (r = 0.65; p < 0.05) and 16 months (r = 0.58; p < 0.05) for men but not women. Progressive long-term exercise significantly influenced EPOC in overweight/obese men but not women. Change in volume of exercise likely explained the increase in energy expenditure during EPOC in men. EPOC contributed modestly to EE compared to the exercise itself.

The Influence of Calcium Consumption on Weight and Fat Following 9 Months of Exercise in Men and Women

BACKGROUND

There is some evidence that calcium consumption improves weight loss during energy restriction but the effects of calcium consumption in conjunction with chronic exercise are unknown.

OBJECTIVE

The purpose of the study was to determine the degree to which calcium consumption influences weight and fat weight change as a result of 9 months of verified supervised exercise in the absence of energy restriction.

METHODS

Participants were 50 previously sedentary, overweight and moderately obese men (n=20) and women (n=30). Exercise of moderate intensity was performed for 45 min/d, 5 d/wk, under supervision. Diet intake was ad libitum and was measured for energy, macronutrient and micronutrient composition at baseline, 4 and 9 months by use of observer recorded weighed plate waste and multiple-pass 24-h dietary recall procedures.

RESULTS

Average calcium consumption was 987 +/- 389 mg/day for men and 786 +/- 276 mg/day for women. Weight change over the 9 months was -4.6 +/- 4.6 kg for men and 0.2 +/- 3.3 kg for women. Calcium consumption was associated with weight change (r =-0.47, p<0.05) in men. The calcium to protein ratio was associated with weight change (r=0.56) and fat weight change (r=-0.53) in men. There was no observed association between calcium and weight or fat weight change in women.

CONCLUSION

Weight and fat weight loss as a result of nine months of moderate intensity exercise may be improved by increased calcium consumption in men but was not observed in women.

Fatness, fitness, and insulin sensitivity among 7- to 9-year-old children

OBJECTIVE

The purpose of this study was to examine the relationships among fatness and aerobic fitness on indices of insulin resistance and sensitivity in children.

RESEARCH DESIGN AND METHODS

A total of 375 children (193 girls and 182 boys) 7 to 9 years of age were categorized by weight as normal-weight, overweight, or obese and by aerobic fitness based on a submaximal physical working capacity test (PWC). Fasting blood glucose (GLU) and insulin (INS) were used to calculate various indices of insulin sensitivity (GLU/INS), the homeostasis model assessment (HOMA), and the quantitative insulin sensitivity check index (QUICKI). Surrogate measures of pancreatic beta cell function included the insulinogenic index (INS/GLU) and the HOMA estimate of pancreatic beta-cell function (HOMA %B).

RESULTS

Insulin sensitivity and secretion variables were significantly different between the normal-weight children and the overweight and obese subjects. Fasting insulin (FI), HOMA, QUICKI, and INS/GLU were significantly different between the overweight and obese subjects. Likewise, the high fitness group possessed a better insulin sensitivity profile. In general, the normal-weight-high fit group possessed the best insulin sensitivity profile and the obese-unfit group possessed the worst insulin sensitivity profile. Several significant differences existed among the six fat-fit groups. Of particular note are the differences within BMI groups by fitness level and the comparison of values between the normal-weight-unfit subjects and the overweight and obese subjects with high fitness.

CONCLUSIONS

The results indicate that aerobic fitness attenuates the difference in insulin sensitivity within BMI categories, thus emphasizing the role of fitness even among overweight and obese children.

Impact of different levels of weight loss on blood pressure in overweight and obese women

This study sought to determine the impact of different levels of weight loss on blood pressure in overweight/obese women. One hundred fifty-nine overweight/obese women (age 48.7 +/- 9.7, weight 101.3 +/- 18.7 kg, BMI 37.3 +/- 6.6 kg/m(2)) completed a six-month clinical weight loss program that included weekly nutrition, behavior, and exercise instruction. Participants consumed a very-low-energy diet (VLED) for 12 weeks. VLED was followed by four weeks of gradual reintroduction to solid foods. At week 16, participants received a diet to maintain weight or slightly reduce weight (<0.5 lb/week) which they followed for the duration of the study. All lab and blood pressure assessments were performed at baseline and six months. Three groups were formed according to the proportion of weight loss after six months; Group 1 had < 10% (n = 19), Group 2 had 10%-20% (n = 64), and Group 3 had >20% (n = 76) weight loss. Differences in systolic blood pressure (mm Hg) were found in dose response fashion for weight loss at six months with 125 +/- 17 (<10%), 119 +/- 13 (10%-20%), and 117 +/- 15 (>20%; p = 0.005). Differences in diastolic blood pressure (mm Hg) were also found in dose response fashion with 81 +/- 9 (<10%), 77 +/- 9 (10%-20%), and 75 +/- 9 (20%; p = 0.003). These data indicate that increasing weight loss beyond 10% of initial body weight may provide added improvements in blood pressure compared to less than 10% weight loss in overweight or obese women.