Caitlin Mason

Prevalence of class I, II and III obesity in Canada.

Obesity places a substantial burden on public health in Canada, and people with more extreme levels of obesity are at substantially increased risk of premature death. In 2003, Health Canada issued updated guidelines for body weight classification in adults (available at [www.hc-sc.gc.ca/fn-an/

Variability in waist circumference measurements according to anatomic measurement site.

The measurement of waist circumference (WC) is widely advocated as a simple anthropometric marker of health risk; yet there remains no uniformly accepted protocol. This study determined whether the magnitude of WC differs across four measurement sites, and quantified the influence of site on the apparent prevalence of abdominal obesity. The predominantly white sample consisted of 223 men and 319 women (20–67 years). WC was measured using a nonstretching tape at the superior border of the iliac crest, midpoint between the iliac crest and lowest rib, umbilicus, and the minimal waist. Differences in WC across sites were tested using repeated measures ANOVA, adjusted for multiple comparisons. Inter‐ and intraobserver reliabilities across sites were estimated using intraclass correlation. In women, the mean WC for all sites were significantly different from each other, with the exception of the iliac crest and midpoint. In contrast, no significant differences between sites were found in men. Measurement site had an influence on the apparent prevalence of abdominal obesity (>88/102 cm), ranging from 23 to 34% in men and 31 to 55% in women. The reproducibility of WC was high at all sites and was comparable across levels of BMI. In conclusion, the magnitude of WC is influenced by measurement site, particularly in women. Small differences are amplified when dichotomous cut points rather than a continuum are used to define abdominal obesity. Adopting a standard measurement protocol will facilitate the interpretation and clinical utility of WC for obesity‐related risk stratification.

Influence of Central and Extremity Circumferences on All‐cause Mortality in Men and Women

For a given level of adiposity, greater lower body circumferences appear to exert a protective effect on several disease outcomes including cardiovascular disease and diabetes; however, the independent associations between extremity circumferences and mortality have not been widely investigated. The purpose of this study was to determine the independent and shared influences of upper‐ and lower‐body circumferences on the risk of mortality in a population‐based sample of adults. The sample included 10,638 adults 20–69 years of age (5,012 men; 5,626 women) from the nationally representative 1981 Canada Fitness Survey (CFS), who were monitored for over 12 years for mortality. BMI was calculated from measured height and weight. Waist, hip, thigh, calf, and upper arm circumferences were measured using a flexible, nonelastic anthropometric tape. Sex‐specific proportional hazards regression models were used to evaluate the relationship between standardized values (Z‐scores) of extremity circumference measures, waist circumference (WC) and mortality. Age, smoking status, alcohol consumption, and leisure‐time physical activity were collected by questionnaire and were included as covariates. During 131,563 person‐years of follow‐up, there were 340 deaths in men and 231 in women. After mutual adjustment, WC was positively associated with mortality whereas arm, thigh, and calf circumferences were significantly protective in men, and arm and thigh circumferences were protective in women. In conclusion, waist and extremity circumferences appear to have opposite, independent effects on mortality in this sample of Canadians. Independent of BMI and WC, men and women with larger extremity circumferences had a lower risk of mortality.

Effect of the Site of Measurement of Waist Circumference on the Prevalence of the Metabolic Syndrome

Waist circumference (WC) is widely advocated as a marker of health risk and is a key diagnostic criterion for metabolic syndrome (MS); yet, there remains no uniformly accepted measurement protocol. The purpose of this study was to determine whether WC is differentially associated with cardiometabolic risk factors according to its anatomic measurement site and to quantify the impact of measurement site on prevalence of MS. The sample included 520 community-dwelling adults (208 men, 312 women). WC was measured at 4 common sites: the superior border of the iliac crest, midpoint between the iliac crest and the lowest rib, the umbilicus, and minimal waist. Blood pressure at rest was measured, and fasting blood samples were analyzed for concentrations of high-density lipoprotein cholesterol, triglycerides, and glucose. MS was diagnosed according to criteria of the American Heart Association/National Heart, Lung, and Blood Institute. Overall, patterns of association between WC and cardiometabolic risk factors were similar across anatomic locations of measurement. In men, prevalence of MS was the same when WC was measured at the iliac crest, the midpoint, or the umbilicus (21.2%), but was lower (18.3%) using the minimal waist. In women, prevalences of MS were 15.1%, 14.4%, 14.1%, and 13.1% using the umbilicus, iliac crest, midpoint, and minimal waist, respectively. In conclusion, prevalence of MS is modestly influenced by anatomic site of WC measurement. Efforts should be made to standardize the protocol for measurement of WC given its potential to influence research findings and clinical decision-making.

Waist circumference thresholds for the prediction of cardiometabolic risk: is measurement site important?

Background:Waist circumference (WC) is frequently measured in clinical and research settings. Although measurement protocols may differ considerably, a single set of sex-specific cut-points are typically used to denote elevated risk. The purpose of this study was to determine whether the appropriate WC thresholds for identifying cardiometabolic risk vary according to anatomical measurement site.Methods:WC was measured at four common sites in 520 community-dwelling adults (20–66 years): superior border of the iliac crest, midpoint between the iliac crest and the lowest rib, umbilicus and minimal waist. Resting blood pressures and fasting levels of total cholesterol, high-density lipoprotein-cholesterol, triglycerides and glucose were measured. The sensitivity and specificity of current WC thresholds (M: >102 cm/40 inch; W: >88 cm/35 inch) for detecting abnormal risk factor levels were calculated for each WC measurement site, and receiver operating characteristic (ROC) curves were used to select optimal thresholds for identifying individuals with risk factor clustering (⩾2 risk factors).Results:The area under the ROC curve for WC measured at each anatomical site was similar for each risk factor and for the presence of risk factor clustering. However, WC >88/102 cm at the umbilicus showed the greatest sensitivity for all outcomes, whereas measurements at the minimal waist had the best specificity in this sample. The sensitivity of WC >88/102 cm for detecting ⩾2 risk factors ranged from 75 to 89% in women and from 48 to 59% in men, and specificity ranged from 52 to 79% in women and from 77 to 88% in men, across measurement sites.Conclusions:At present, recommended WC thresholds may not have the same clinical utility at all anatomical locations of WC measurement.

Metabolic Syndrome and Prevalent Any-site, Prostate, Breast and ColonCancers in the U.S. Adult Population: NHANES 1999-2010

Background: Metabolic Syndrome (MetS) is associated with elevated risk of diabetes, cardiovascular disease, and premature mortality. To date, however, the association between MetS and obesity-related cancers has not been systematically assessed within a population-based sample. Methods: In order to quantify the association between MetS and its components on any-site, breast, prostate, and colon cancers, data from the U.S. NHANES 1999-2010 (n=15 141, 18-85 years) were used. Results: In general, the prevalence of MetS was higher amongst those with a self-reported history of cancer. Although MetS, its individual components, and total number of components were positively related to odds of any-site, breast, prostate, and colon cancers, this effect was almost entirely eliminated after adjustment for age. In age-adjusted models, elevated blood glucose was associated with higher odds of prostate (OR: 1.67, 95% CI: 1.08-2.56) and colon cancer (OR: 1.60, 95% CI: 1.02-2.53), and a protective effect of low HDL cholesterol on prostate cancer (OR: 0.64, 95% CI: 0.43-0.94). Further adjustment for sex, ethnicity, income, education, smoking, alcohol, and recreational/ leisure-time physical activity had only minimal influence on these associations. In multivariable analyses, no uniform linear trends were observed between the number of MetS components and site-specific cancers. Conclusion: After accounting for covariates, no consistent association between MetS and any-site, breast, prostate, or colon cancer was observed. Further prospective study is necessary to confirm and extend our understanding of the role of age and other risk factors on the inter-relationship between metabolic health and cancer.

Application of obesity treatment algorithms to Canadian adults

Objective:The purpose of this study was to apply obesity treatment algorithms to a representative sample of Canadians to determine their potential impact on the population.Design:The Canadian Heart Health Surveys (1986–1992) were used to describe the prevalence of adults (18–64 y) that would be eligible for weight loss treatment according to the US NIH algorithm, which uses body mass index (BMI), waist circumference (WC), and the presence of two or more cardiovascular disease (CVD) risk factors. Similar algorithms based on CVD risk factors and a single measure of either BMI or WC alone were also evaluated.Results:Using the NIH algorithm, 24% of Canadians (28% men, 19% women) would be identified for weight loss treatment. Virtually, all subjects received the same treatment recommendations when using BMI and CVD risk factors only, while 22% (23% men, 21% women) would meet the criteria for treatment using WC and CVD risk factors only.Conclusions:Approximately one in four Canadians would be eligible for weight loss treatment using the NIH obesity treatment algorithm. However, the algorithm may be improved through the incorporation of more sensitive WC thresholds.

ORIGINAL RESEARCH: Opposing Effects of Waist and Extremity Circumferences on the Risk of Incident Type 2 Diabetes

ABSTRACT OBJECTIVE: To investigate the relationship between anthropometric circumferences and incident type 2 diabetes in Canadian adults. METHODS: The sample included 516 men and 579 women from the Physical Activity Longitudinal Study. Waist, hip, thigh and upper arm circumferences were used to predict incident diabetes over 15.5 years of follow-up. The odds of developing diabetes associated with 1 standard deviation of each anthropometric measure was calculated using sex-specific logistic regression, adjusted for age and parental history of diabetes. RESULTS: There were 56 new cases of diabetes, yielding a 15.5 year cumulative incidence of 5.1%. With the exception of arm and thigh circumferences in men, all of the anthro-pometric variables were positive predictors of diabetes. However, after adjustment for body mass index (BMI) and waist circumference (WC), the nature of the associations between hip, thigh and arm circumferences and diabetes reversed, such that they became inversely associated with diabetes development. The positive association between WC and incident diabetes was independent of all other circumference measures but was attenuated by BMI. CONCLUSIONS: Larger extremity circumferences are associated with a lower risk of incident diabetes after adjustment for overall and abdominal adiposity, highlighting the potential value of these measures above and beyond the routine measurement of BMI and WC.