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Population monitoring of obesity is most commonly conducted using body mass index (BMI). We test the hypothesis that because of increases in waist circumference (WC) independent of increases in weight, BMI alone detects an increasingly smaller proportion of the population with obesity., Methods: Australian adults with measured height, weight, and WC were selected from three nationally representative cross-sectional surveys (1989, 1999-2000, 2011-12; n=8313, 5903 & 3904). Participants were defined as having obesity using classifications for an obese BMI (≥30kg·m -2 ) and substantially-increased-risk WC (≥88cm [women], ≥102cm [men]). Age-standardised prevalence of obesity according to BMI and/or WC, and the proportion of these detected by BMI and by WC were compared across surveys., Findings: Between 1989 and 2011-12, weight and WC increased by 5.4kg and 10.7cm (women), and by 7.0kg and 7.3cm (men). For women and men, 63% and 38% of increases in WC were independent of increases in weight. Over this period, the prevalence of obesity according to BMI and/or WC increased by 25.3 percentage-points for women (18.9% to 44.3%) and 21.1 percentage-points for men (17.1% to 38.2%). The proportion of these detected by BMI decreased for women by 20 percentage-points (77% to 57%) with no change for men. The proportion of these detected by WC increased for women and men by 10 percentage-points (87% to 97%) and 6 percentage-points (85% to 91%) respectively., Conclusion: BMI alone is detecting a decreasing proportion of those considered obese by BMI and/or WC. Renewed discussion regarding how we monitor obesity at the population level is required., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Underlying blood pressure is that observed in the absence of antihypertensive treatment or, among those treated, the estimate of that which would be observed without treatment. This study aims to examine the relationships between diabetes or obesity and underlying systolic blood pressure adjusted for antihypertensive treatment by several methods., Methods: Data from two population studies were analyzed-an American Indian community in Arizona and the National Health and Nutrition Examination Surveys. Antihypertensive treatment was accounted for using: no adjustment; antihypertensive use as a covariate; blood pressure dichotomized into normotension and hypertension; addition of a fixed treatment effect; non-parametric algorithm; and censored normal regression., Results: The magnitude of association at each time point differed by adjustment method particularly where there was a difference in prevalence of antihypertensive use between people with and without diabetes or obesity. The common methods of ignoring antihypertensive treatment or including it as a covariate in a regression model underestimated the effects of diabetes and obesity on underlying blood pressure, compared to the recommended method of the censored normal regression., Conclusion: Proper accounting for antihypertensive treatment is needed in interpreting variables that affect blood pressure., (Published by Elsevier Inc.)

Objective: To compare a simple measure - age of onset of obesity - to an obese-years construct (a product of duration and magnitude of obesity) as risk factors for type 2 diabetes., Method: Participants from the Framingham Heart Study who were not obese and did not have diabetes at baseline were included (n=4,320). The Akaike Information Criterion (AIC) was computed to compare four Cox proportional hazards models with incident diabetes as the outcome and: (i) obese-years; (ii) age of onset of obesity; (iii) body mass index (BMI); and (iv) age of onset of obesity plus magnitude of BMI combined, as exposures., Results: AIC indicated that the model with obese-years provided a more effective explanation of incidence of type 2 diabetes compared to the remaining three models. Models including age of onset of obesity plus BMI were not appreciably different from the model with BMI alone, except in those aged ≥60., Conclusions: While obese-years was the optimal obesity construct to explain risk of type 2 diabetes, age of onset may be a useful, practical addition to current BMI in the elderly., Implications: Where computation of obese-years is not possible or impractical, age of onset of obesity combined with BMI may provide a useful alternative., (© 2016 Public Health Association of Australia.)

Objective: To determine the risk of mortality associated with and quantify the deaths attributable to combinations of body mass index (BMI) and waist circumference (WC)., Methods: This study included 41,439 participants. For the hazard ratio (HR) calculation, adiposity categories were defined as: BMI(N) /WC(N) , BMI(N) /WC(O) , BMI(O) /WC(N) , and BMI(O) /WC(O) (N = non-obese, O = obese). For the population attributable fraction analysis, obesity was classified as: (i) obese by BMI and/or WC; (ii) obese by BMI; and (iii) obese by WC. Mortality data was complete to the end of 2012., Results: The prevalence of BMI(N) /WC(N) , BMI(N) /WC(O) , BMI(O) /WC(N) , and BMI(O) /WC(O) was 73%, 6%, 6%, and 15%, respectively. There was an increased risk of all-cause and cardiovascular disease (CVD) mortality in those with BMI(N) /WC(O) (HR (95% CI) 1.2 (1.2, 1.3) and 1.3 (1.1, 1.6)) and BMI(O) /WC(O) (1.3 (1.3, 1.4) and 1.7 (1.5, 1.9)) compared to those with BMI(N) /WC(N) . The estimated proportion of all-cause and CVD mortality attributable to obesity defined using WC or using BMI and/or WC was higher compared to obesity defined using BMI., Conclusions: Current population obesity monitoring misses those with BMI(N) /WC(O) who are at increased risk of mortality. By targeting reductions in population WC, the potential exists to prevent more deaths in the population than if we continue to target reductions in BMI alone., (© 2016 The Obesity Society.)

Introduction: There is a paucity of data examining the effects of weight change on knee joint structures and symptoms. This study examined the effect of weight change on change in knee cartilage volume and symptoms in an obese cohort., Methods: 112 obese subjects (Body Mass Index ≥30 kg/m(2)) were recruited from various community sources to examine the effect of obesity on musculoskeletal health. Tibial cartilage volume, determined by MRI, and knee symptoms, determined by the Western Ontario and McMaster Osteoarthritis Index (WOMAC) were collected at baseline and an average of 2.3 years later., Results: Percentage weight change was associated with change in medial tibial cartilage volume (β -1.2 mm(3), 95% CI -2.3 to -0.1 mm(3), p=0.03) that was consistent throughout the spectrum of weight loss through to mild weight gain. Percentage weight change was not associated with change in the lateral tibial (p=0.93) or patella (p=0.32) cartilage volumes. Percentage weight change was associated with change in all WOMAC subscales (all p≤0.01): pain (β -1.8 mm, 95% CI -3.2 to -0.4 mm), stiffness (β -1.6 mm, 95% CI -2.5 to -0.7 mm) and function (β -6.9 mm, 95% CI -11.6 to -2.1 mm)., Conclusions: The linearity of effect implies that weight loss is associated with reduced medial cartilage volume loss and improved knee symptoms, while weight gain is associated with increased medial cartilage volume loss and worse knee symptoms. These results suggest that in obese people, small amounts of weight change may have the potential for a disease modifying effect on both knee joint structure and symptoms. While weight loss is an important primary management strategy in obese individuals, avoidance of further weight gain should also be a clinical goal., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Background: Previous studies exploring the association between obesity and hypertension generally used a single baseline measurement of obesity. The effect of accumulating excess adiposity over time on the risk of hypertension is uncertain. This study aimed to examine the relationship between duration of obesity and incident hypertension using the Framingham Heart Study., Methods: Two thousand, nine hundred and fifty-three participants aged 30-62 years without baseline hypertension were included. Blood pressure, height and weight were measured biennially. Duration of obesity was calculated. Time to incident hypertension was analysed using time-varying Cox proportional hazards regression with age as the time scale and censoring at time of death or end of follow-up., Results: Eighty percent of participants developed hypertension (median follow-up 15.9 years). A positive association between obesity duration and incident hypertension was observed in women. There was no longer an association when time-varying BMI was adjusted for (hazard ratio 0.95; (95% confidence interval 0.85-1.05))., Conclusion: These findings suggest that the mechanism by which excess adiposity may increase blood pressure is primarily immediate and that long-term exposure to obesity does not further increase the risk of developing hypertension beyond the level of BMI attained.

Objective: To relate measured obesity duration in mid-life with subsequent incidence of physical disability over and above body mass index (BMI) attained., Methods: Framingham Offspring Study is a longitudinal study that began in 1971. Examination 5 (1991-1995; "baseline") and disability onset ascertained from examinations 6-8 (2008) were used. About 2,095 disability-free participants aged 45-65 years at baseline were included. Obesity (BMI ≥ 30 kg/m(2) ) duration was calculated between examination 1 and examination 5. Cox regression was used to analyze time to disability., Results: 204 participants developed disability (incidence rate=7.9 per 1,000 person-years). Obesity duration ranged from 0 to 22 years (mean of 2.0 years overall, 8.3 years for those with baseline obesity). Obesity duration increased risk of new disability (hazard ratio [HR] 1.07 per year of obesity; 95% confidence interval [CI] 1.05-1.09). This association was attenuated on further adjustment for baseline BMI (HR 1.03; 95% CI 1.00-1.06)., Conclusions: Being obese for longer during mid-life increases the risk of later-life disability over and above attained BMI. These results support the need for prevention of weight gain in young adults to avoid an increasing burden of physical disability in later life., (© 2014 The Obesity Society.)

Obesity is a risk factor for osteoarthritis. Antiretroviral therapy (ART)-treated HIV-infected patients are frequently affected by overweight and obesity, and may be at increased risk of osteoarthritis. BMI however is a measure which does not discriminate adipose from non-adipose body mass, or fat distribution, which may have different effects. This study aimed to examine relationships between body composition and knee cartilage volume, as assessed by magnetic resonance imaging in HIV infection. 35 ART-treated HIV-infected men aged 51.7 years (mean) 7.9 (SD) and 18 healthy men aged 49.5 years (mean) 6.4 (SD) participated. Cartilage volume was measured on magnetic resonance imaging of the dominant knee using validated methods. Body composition was measured using dual x-ray absorptiometry. HIV-infected participants had less total body and gynoid fat (kg) (p = 0.04 and p = 0.007, respectively) and more percent android fat mass and percent trunk fat mass (p = 0.001 and p < 0.001, respectively) than controls. In HIV-infected participants there was an inverse association between total body fat mass and average tibial cartilage volume (R = -8.01, 95% CI -15.66, -0.36). Also, in HIV-infected participants there was an inverse association between android fat mass and average cartilage volume (R = -90.91, 95% CI -158.66, -23.16). This preliminary study found that both total body and android fat mass were inversely related to average knee cartilage volume in ambulant, ART-treated HIV-infected adults. These findings are features of early knee osteoarthritis and this may be of future significance in HIV., (© The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.)

Objective: To examine the association between obese-years and the risk of cardiovascular disease (CVD)., Study Design: Prospective cohort study., Setting: Boston, USA., Participants: 5036 participants of the Framingham Heart Study were examined., Methods: Obese-years was calculated by multiplying for each participant the number of body mass index (BMI) units above 29 kg/m(2) by the number of years lived at that BMI during approximately 50 years of follow-up. The association between obese-years and CVD was analysed using time-dependent Cox regression adjusted for potential confounders and compared with other models using the Akaike information criterion (AIC). The lowest AIC indicated better fit., Primary Outcome Cvd Results: The median cumulative obese-years was 24 (range 2-556 obese-years). During 138,918 person-years of follow-up, 2753 (55%) participants were diagnosed with CVD. The incidence rates and adjusted HR (AHR) for CVD increased with an increase in the number of obese-years. AHR for the categories 1-24.9, 25-49.9, 50-74.9 and ≥75 obese-years were, respectively, 1.31 (95% CI 1.15 to 1.48), 1.37 (95% CI 1.14 to 1.65), 1.62 (95% CI 1.32 to 1.99) and 1.80 (95% CI 1.54 to 2.10) compared with those who were never obese (ie, had zero obese-years). The effect of obese-years was stronger in males than females. For every 10 unit increase in obese-years, the AHR of CVD increased by 6% (95% CI 4% to 8%) for males and 3% (95% CI 2% to 4%) for females. The AIC was lowest for the model containing obese-years compared with models containing either the level of BMI or the duration of obesity alone., Conclusions: This study demonstrates that obese-years metric conceptually captures the cumulative damage of obesity on body systems, and is found to provide slightly more precise estimation of the risk of CVD than the level or duration of obesity alone., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Objective: This study aimed to describe the changes in weight and waist circumference (WC), examine the incidence of obesity as defined by body mass index (BMI) and WC, and describe the changes in the prevalence of obesity over 12 years., Methods: In 1999/2000, 11,247 adults aged ≥25 years were recruited from 42 randomly selected areas across Australia. In total, 44.6% of eligible participants completed follow-up in 2011/12. Height, weight, and WC were measured at both surveys., Results: People who were 25-34 years of age at baseline gained an average of 6.7 kg weight and 6.6 cm WC, whereas those aged ≥75 years lost an average of 4.5 kg and gained an average of 0.8 cm. Women had a greater increase in WC than men, but did not differ in terms of weight gain. The 12-year incidence of obesity was 15.0% when defined by BMI and 31.8% when defined by WC. According to BMI and WC combined, the percentage of the cohort that was normal weight decreased from 33 to 21% and the percentage that was obese increased from 32 to 49% between baseline and 2012., Conclusions: In addition to BMI, assessment of WC should be incorporated more frequently when assessing population trends of obesity and the burden of disease associated with excess adiposity., (Copyright © 2014 The Obesity Society.)

Objective: To examine the longitudinal association between significant weight change and change in knee symptoms (pain, stiffness, and function), and to determine whether the effects differ in those who are obese and those with osteoarthritis (OA)., Methods: Two hundred fifty subjects ranging from normal weight to obese (body mass index range 16.9-59.1 kg/m(2) ) and no significant musculoskeletal disease were recruited from the general community and weight loss clinics and organizations. Seventy-eight percent were followed at ~2 years. Weight, height, and knee symptoms (using the Western Ontario and McMaster Universities Osteoarthritis Index) were assessed at baseline and followup. Any weight loss methods were recorded., Results: Thirty percent of subjects lost ≥5% of baseline weight, 56% of subjects' weight remained stable (loss or gain of <5% of baseline weight), and 14% of subjects gained ≥5% of baseline weight. Using estimated marginal means, weight gain was associated with worsening pain (mean 27.1 mm; 95% confidence interval [95% CI] -1.1, 55.2), stiffness (mean 18.4 mm; 95% CI 1.5, 35.3), and function (mean 99.3 mm; 95% CI 4.0, 194.6) compared to stable weight. Weight loss was associated with reduced pain (mean -22.4 mm; 95% CI -44.4, -0.3), stiffness (mean -15.3 mm; 95% CI -28.50, -2.0), and function (mean -73.2 mm; 95% CI -147.9, 1.3) compared to stable weight., Conclusion: Weight gain was associated with adverse effects on knee symptoms, particularly in those who are obese and who have OA. Although losing weight is potentially beneficial for symptom improvement, the effects were more modest. Avoiding weight gain is important in managing knee symptoms., (Copyright © 2013 by the American College of Rheumatology.)

Objective: To examine the relationship between obesity, body composition, and foot pain as assessed by the Manchester Foot Pain and Disability Index (MFPDI)., Methods: Subjects 25-62 years of age (n = 136) were recruited as part of a study examining the relationship between obesity and musculoskeletal health. Foot pain was defined as current foot pain and pain in the last month, and an MFPDI score of ≥1. Body composition (tissue mass and fat distribution) was measured using dual x-ray absorptiometry., Results: The body mass index (BMI) in this population was normally distributed around a mean of 32.1 kg/m(2). The prevalence of foot pain was 55.1%. There was a positive association between BMI and foot pain (odds ratio [OR] 1.11, 95% confidence interval [95% CI] 1.06-1.17). Foot pain was also positively associated with fat mass (OR 1.05, 95% CI 1.02-1.09) and fat mass index (FMI; OR 1.16, 95% CI 1.06-1.28) when adjusted for age, sex, and skeletal muscle mass and age, sex, and fat-free mass index (FFMI), respectively. When examining fat distribution, positive associations were observed for android/total body fat ratio (OR 1.42, 95% CI 1.11-1.83) and android/gynoid fat ratio (OR 35.15, 95% CI 2.60-475.47), although gynoid/total body fat ratio was inversely related to foot pain (OR 0.83, 95% CI 0.73-0.93). Skeletal muscle mass and FFMI were not associated with foot pain when adjusted for fat mass or FMI, respectively., Conclusion: Increasing BMI, specifically android fat mass, is strongly associated with foot pain and disability. This may imply both biomechanical and metabolic mechanisms., (Copyright © 2012 by the American College of Rheumatology.)