The American College of Sports Medicine advocates the use of a percentage of maximal oxygen uptake reserve (%VO2R) for exercise prescription purposes because it's thought to provide a close match with percentage of heart rate reserve (%HRR) than a given percentage of maximal oxygen uptake (%VO2max). However, some recent studies have challenged the validity of this matching. The purpose of this study was to assess the association of body mass index (BMI) with the matching of %HRR and %VO2R during graded exercise testing. The study sample included 626 subjects (281 men; 345 women); mean age of 45.5+11.7 years; mean BMI of 27.9+5.4 kg .m-2) who completed a maximal treadmill test to volitional fatigue using the BSU/Bruce Ramp protocol. The distribution of BMI measures within the sample was 31.4% <25; 38% between 25.0 and 29.9; 17.9% between 30 and 34.9%; 8.8% between 35 and 39.9%; and 3.1% were > 40 kg•m"2. Subjects were excluded from the analysis if they failed to achieve a peak RER > LO during the maximal exercise test, possessed pulmonary or cardiovascular disease (excluding hypertension), or incomplete/erroneous submaximal heart rate and/or V02 data that was unable to be retrieved from subject's existing file. Heart rate and VO2 data from minutes 3, 6, and 9 were converted into %HRR and %VO2R, with 3.5 ml•kg-'•min' serving to represent resting VO2. The relative exercise intensity for minutes 3, 6, and 9 represented 39.7 +12.2, 62.9 ± 15.6, and 80.8 ± 12.5% of VO2R, respectively and 43.1 f 12.6, 64.7 ± 14.9, and 83.5 + 10.6% of HRR. %HRR significantly overestimated %VO2R at each measurement point during the exercise test with mean differences 3.3, 2.0, and 3.8%, respectively (p<0.05). The association of BMI with the matching of %HRR and %VO2R was assessed by correlation with the difference the scores (AHRRVO2R) at each specified time during exercise test. Correlations for BMI and AHRRVO2R were -0.102, -0.175, and -0.231 for minutes 3,6, and 9, respectively (p<0.05). These results demonstrate a low association between BMI and the matching of HRR and VO2R. / School of Physical Education, Sport, and Exercise Science

Heightened reward associated with palatable food, a construct referred to as hedonic reward, can promote excessive energy intake among adults. However, no known studies have examined the influence of hedonic reward on adolescents' eating behavior and weight status. The present study examined whether there was an association between hedonic hunger and weight status in overweight/obese adolescents and whether dietary behavior (caloric consumption) mediated this association. Baseline measures of body mass index, hedonic food reward, and dietary intake were collected from one hundred overweight and obese adolescents. Data were analyzed using mixture modeling. Mediation at varying levels of hedonic hunger was explored and three heterogeneous sub-classes were identified. Results indicated that for 65% participants there was a positive association between hedonic hunger and zBMI such that one unit of increase in hedonic hunger was associated with a 0.35 unit increase in zBMI. However, no conclusive evidence of caloric intake mediating the association between hedonic hunger and weight-status was found. Overall, our results suggest that exaggerated hedonic responses are associated with higher body mass in adolescents. These results provide a compelling argument that hedonic hunger can potentially override the homeostatic need for energy and may be associated with weight-gain.

Obesity results from a complex interaction between diet, physical activity, and the environment. The purposes of this study were to identify behaviors associated with resilience to childhood obesity, and to compare the sensitivity of the Figure Rating Scales (FRS) in reflecting Body Mass Index (BMI). Fifty health professionals in nutrition and 35 low-income, parent-and-child pairs completed the study. Children aged 6-11, perceived as “normal-weight” by their parents, were recruited. Five children had a measured BMI above the 85th percentile. Using a picture-sort method, each participant responded to a series of questions about 13 childhood obesity-related messages. Results included comparison between health professionals, parents, and children about 1) familiarity toward each message, 2) frequency in following the recommendation, 3) perception of ease for others to follow, and 4) perception of effectiveness to help prevent childhood obesity. Health professionals and parents had similar familiarity regarding all 13 messages. However, in terms of practicality, health professionals and parents differed significantly in eight messages that they reported “always taught/followed,” seven messages that they “sometimes taught/followed,” and two messages that they “seldom or never taught/followed.” In most messages, children’s observation about what the family followed differed from what parents reported following. In terms of ease for others to follow “Watch portion sizes” and “Tell children to eat all of the meal before getting dessert,” health professionals and parental perception differed significantly. In terms of effectiveness in childhood obesity prevention, health professionals and parents agreed on 12 of 13 messages. Health professionals did not find message “Tell children to eat all of the meal before getting dessert” to be effective in preventing childhood obesity, whereas parents did. FRS and measured BMI were significantly correlated among health professionals (r=0.75), parents (r=0.72), and children (r=0.53 for children ages 8-11, r=0.64 when a mother selected a silhouette for her child). For different subgroups, parent-and-child silhouette selection was closely correlated (r= 0.84). However, correlation between child’s BMI percentile and silhouette was nonsignificant in most subgroups (r= 0.47). In conclusion, FRS was effective among adults and older children (aged ≥8) in reflecting BMI but not among younger children (aged 6-7).

In light of alarming rises in the prevalence of obesity worldwide, tackling the obesity ‘epidemic’ is now a national health priority in many countries. Increasingly, population measures that provide accurate estimates of body fatness in children are required. Body mass index (BMI), or weight standardised for height, remains the most cost-effective and practical tool in this regard. However, there is evidence that the association between BMI and body fatness is variable in children from different ethnic backgrounds. The primary aim of this thesis was to investigate the appropriateness of BMI thresholds for defining overweight and obesity in female children and adolescents from five diverse ethnic groups. Secondary objectives were to examine the associations between weight control practices and perceptions, and to compare objectively-measured physical activity levels with participation in active transport (AT). In order to achieve the primary aim stated above, it was necessary to obtain valid and reliable measures of body fat percentage (%BF) in a large sample of children. Bioelectrical impedance analysis (BIA) is well suited for this purpose, providing a portable and cost-effective means to estimate fat-free mass (and subsequently %BF). While equations exist for European, Maori, and Pacific Island children, findings from the preliminary study described in Chapter 2 demonstrate that there are no BIA equations appropriate for Chinese and Indian children. Given that these two groups are two of the fastest growing ethnicities in New Zealand, a new equation was developed that enables Asian girls to be included in future BIA research. The main study of this thesis involved a large-scale investigation of body composition in New Zealand’s five major ethnic groups (European, Maori, Pacific Island, East Asian, and South Asian). A total of 1,081 adolescent girls aged 11-16 years participated in the Girls’ Activity and Body Composition (ABC) Study. To extend the age range, data were combined with another study of 5-11-year-old New Zealand children (595 girls), coined the Body-Size and Steps in Children (BASIC) Study. Both studies measured BMI from height and weight, %BF from bio impedance measurements, and physical activity using sealed multiday memory pedometers over five consecutive days. A questionnaire was also administered to the adolescent-aged girls to gather data related to weight perceptions and practices. Initial analyses of the main dataset demonstrated that existing BMI definitions of overweight were relatively insensitive for predicting excess %BF in South and East Asian girls. Conversely, low specificity was observed for Pacific Island and Maori children. These findings provided the rationale for the second set of analyses: the development of BMI cut-off points that correspond to an equivalent level of %BF across all ethnicities. The adjusted BMI curves for overweight and obesity ranged from an average of 3.3 and 3.8 kg.m-2 (respectively) lower than international standards in South Asian girls to 1.5 and 1.9 kg.m-2 higher in Pacific Island girls. Clearly, the proposed changes will have significant effect on our estimates of overweight and obesity in this population group. Subsequent investigation revealed that many adolescent girls misclassify their weight status. However, the number of girls trying to lose weight exceeded those who perceived themselves as being overweight, with the magnitude of the difference dependent on ethnicity. It was concluded that interventions and educational campaigns that assist girls in recognising a state of excess body fat are a priority for all ethnic groups to ensure that behavioural changes necessary to combat widespread overweight and obesity are adopted. Finally, it was observed that the physical activity levels of the participants were significantly lower on weekends (9,528  4,407) than on weekdays (12,597  3,630). Furthermore, a consistent decline in daily step counts was observed with age: after adjustment for ethnicity and socioeconomic status (SES), girls in school years 9-10 achieved 2,469 (weekday) and 4,011 (weekend) fewer steps than girls in years 1-2. Daily step counts also varied by ethnicity, with Maori girls the most active and South Asian girls the least active. Overall, girls who used AT to and from school averaged 1,052 more weekday steps than those who did not use AT. These data suggest that adolescent-aged girls and girls of Asian descent are priority groups for future physical activity interventions, and that the promotion of AT in girls appears to be worthwhile.

Thesis (Ph. D.)--Case Western Reserve University, 2007. / [School of Medicine] Department of Epidemiology and Biostatistics. Includes bibliographical references. Available online via OhioLINK's ETD Center.

This thesis explores race and gender differences in perceptions and behaviors regarding weight and obesity, along with the relative influence of individual and structural factors on the personal weight status of black and white adults. In addition, this study examines the extent to which black and white adults differ in their perceptions of discrimination attributed to their personal weight. Based on an analysis of data from a national poll conducted by ABC News and TIME magazine, results indicate that weight status perceptions of overweight black females were consistent, while incongruity was found in perceived and actual weight status among obese black women. On the other hand, a greater proportion of obese white women under-assessed their weight status compared to obese black women. However, regardless of race, men were more likely to under-assess their weight than women. There were no differences by race and gender in reports of having felt discriminated against because of personal weight status. Findings also revealed that black females and males face greater constraints than their white counterparts related to controlling weight and fighting obesity, including such factors as a lack of information on how to establish good eating habits, the need to monitor food content, and being able to afford the cost of purchasing healthy food. A discussion of these findings in relation to previous research is provided along with recommendations for further study.

In Canada, the prevalence of childhood overweight and obesity has increased dramatically since the 1980s. Few studies have examined factors associated with overweight and obesity in Canadian children. The purpose of this study was to: (1) explore the relationship between physical activity and BMI, (2) examine the prevalence of childhood overweight and obesity, and (3) explore the importance of age, gender, and residency (farm versus town) in relation to childhood overweight and obesity in a sample of rural Saskatchewan children.<p>This cross-sectional study included a self-report questionnaire survey and anthropometric assessment of a sample of children (Grades 4-6) from rural Saskatchewan. Of the 525 questionnaires distributed, 262 were completed with a signed consent form (response rate: 49.9%) and 251 of those students had their height, weight, and sitting height measured. The research questionnaire gathered demographic data about the child and the parents or guardian, data on the childs sedentary leisure activities, and a 7 day physical activity history using the Physical Activity Questionnaire for Older Children (PAQ-C). Each childs body mass index was estimated using the measured height and weight and these estimates were compared to international standards for BMI to estimate the prevalence of childhood overweight (25.5%) and obesity (7.1%) within the study population. There were no statistically significant gender differences in the proportion of children who were overweight or obese. The factors found to consistently have a significant association with the prevalence of overweight and obesity were Aboriginal descent and mothers and fathers BMI category. The mean PAQ-C score was similar for boys (3.3, SD = 0.64) and girls (3.2, SD = 0.57) and did not differ significantly by BMI category. <p>This descriptive study provided information on the prevalence of physical activity, overweight, and obesity in a sample of rural Saskatchewan children and the relationship between physical activity and BMI in the sample. Findings of this study can be used by nurses, other health professionals, and education leaders to develop health promotion programs to promote a healthier lifestyle for children and their families.

In Canada, the prevalence of childhood overweight and obesity has increased dramatically since the 1980s. Few studies have examined factors associated with overweight and obesity in Canadian children. The purpose of this study was to: (1) explore the relationship between physical activity and BMI, (2) examine the prevalence of childhood overweight and obesity, and (3) explore the importance of age, gender, and residency (farm versus town) in relation to childhood overweight and obesity in a sample of rural Saskatchewan children.<p>This cross-sectional study included a self-report questionnaire survey and anthropometric assessment of a sample of children (Grades 4-6) from rural Saskatchewan. Of the 525 questionnaires distributed, 262 were completed with a signed consent form (response rate: 49.9%) and 251 of those students had their height, weight, and sitting height measured. The research questionnaire gathered demographic data about the child and the parents or guardian, data on the childs sedentary leisure activities, and a 7 day physical activity history using the Physical Activity Questionnaire for Older Children (PAQ-C). Each childs body mass index was estimated using the measured height and weight and these estimates were compared to international standards for BMI to estimate the prevalence of childhood overweight (25.5%) and obesity (7.1%) within the study population. There were no statistically significant gender differences in the proportion of children who were overweight or obese. The factors found to consistently have a significant association with the prevalence of overweight and obesity were Aboriginal descent and mothers and fathers BMI category. The mean PAQ-C score was similar for boys (3.3, SD = 0.64) and girls (3.2, SD = 0.57) and did not differ significantly by BMI category. <p>This descriptive study provided information on the prevalence of physical activity, overweight, and obesity in a sample of rural Saskatchewan children and the relationship between physical activity and BMI in the sample. Findings of this study can be used by nurses, other health professionals, and education leaders to develop health promotion programs to promote a healthier lifestyle for children and their families.

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