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We identify gaps in the knowledge, including the refinement of waist circumference threshold values for a given BMI category, to optimize obesity risk stratification across age, sex and ethnicity. Excess lipid accumulation in VAT and ectopic depots is associated with increased cardiometabolic risk4749. Fig 1. These findings provide a plausible mechanism by which lower values for BMI or hip circumference for a given waist circumference would increase adverse health risk. When there are no extreme values, the mean is the preferred measure of a typical value, in part because each observation is considered in the computation of the mean. When there is an even number of observations in the sample (e.g., n=10) the median is defined as the mean of the two middle values in the ordered data set. Associations between general and abdominal adiposity and mortality in individuals with diabetes mellitus. Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates. Among children, obesity was associated with $116 (95% CI $14-$201) excess costs per person and $1.32 billion (95% CI $0.16-$2.29) of medical spending, with severe obesity associated with $310 (95% CI $124-$474) excess costs per child. But judging whether a person is obese based only on their size is old-fashioned and not terribly useful, he says. Evidence from several reviews and meta-analyses confirm that, regardless of age and sex, a decrease in energy intake through diet or an increase in energy expenditure through exercise is associated with a substantial reduction in waist circumference7887. Is there now a better way to determine body composition? For example, in a study of >2,000 older participants from the Health, Ageing and Body Composition study, Marieke Snijder and colleagues were among the first to report that thigh adipose tissue mass is negatively associated with glucose intolerance and dyslipidaemia, after accounting for abdominal adipose tissue mass47. Disclaimer. The influences of height and age on waist circumference as an index of adiposity in adults. and 0.75 grams). There are two main variable transformations: Lets say we are interested in babies ages. In the sample of n=10 diastolic blood pressures, the two middle values are 70 and 72, and thus the median is (70+72)/2 = 71. You've probably heard the term BMI (body mass index). It is not presented instead of either the mean or the median, but rather in addition to the mean or median. Missing data occurs in studies for a variety of reasons. Spencer EA, Roddam AW, Key TJ. Coutinho T, et al. Here X=diastolic blood pressure. Dr. Weil on Healthy Aging for Nutrition Want to change your diet? Federal government websites often end in .gov or .mil. The effect of exercise on visceral adipose tissue in overweight adults: a systematic review and meta-analysis. Moreover, we describe evidence that clinically relevant reductions in waist circumference can be achieved by routine, moderate-intensity exercise and/or dietary interventions. However, a 28-year-old man could actually be 28 years, 7 months, 16 days, 3 hours, 4 minutes, 5 seconds, 31 milliseconds, 9 nanoseconds old. Slentz CA, et al. Distance: The distance (in feet) that a baseball player hit the ball. R.R., I.J.N. Lincoff AM, et al. Other alternatives to waist circumference have included the conicity index32 and the abdominal obesity index33, but they are, at best, only slightly better predictors of disease risk than waist circumference alone. If you face this kind of setup, do not forget to transform your variable into the right type before performing any statistical analyses. Front Nutr. The benefits associated with reductions in waist circumference might be observed with or without a change in BMI. Greenland P, et al. Some discrete variables are inherently ordinal. Exercise and/or diet consistent with guideline recommendations are associated with substantial reductions in waist circumference, independent of age, sex or ethnicity. Generally, it's the belly fat, or the "apple" shape, that has a higher health risk. Methods: We estimated continuous BMI-related health care expenditures using data from the Medical Expenditure Panel Survey (MEPS) 2011-2016 for 175,726 respondents. It is also often the case (especially in surveys) that the variable salary (quantitative continuous) is transformed into a qualitative ordinal variable with different range of salaries (e.g., < 1000, 10002000, > 2000). The median is unaffected by extreme or outlying values. Content 2016. O'Neill, T., Shalev-Goldman, E. & Ross, R. in. Discrete vs. The research team that conducted the latest study also tested their participants levels of leptin, a hormone secreted by body fat, and reported that the results seem to mirror DEXA findings. The frequencies, or numbers of participants in each response category, are shown in the middle column and the relative frequencies, as percentages, are shown in the rightmost column. Yoon YS, Oh SW. Optimal waist circumference cutoff values for the diagnosis of abdominal obesity in Korean adults. For example, Ian Janssen and colleagues examined the changes in waist circumference for a given BMI over a 30-year period in a Canadian sample35. They contended that the BMI number that now signals obesity - 30 - should be lowered to 24 for women and 28 for men. Continuous b. Discrete c. Ordinal d. Dichotomous 7. Despite the existence of a robust statistical association with all-cause death independent of BMI, there is no solid evidence that addition of waist circumference to standard cardiovascular risk models (such as FRS62 or PCE63) improves risk prediction using more stringent statistical benchmarks. Is waist circumference per body mass index rising differentially across the United States, England, China and Mexico? For example, Robert Ross and colleagues conducted a large RCT whereby participants (n=300) were assigned to either a control arm or an intervention arm with different exercise levels: low, defined as 180 kcal per session for women and 300 kcal per session for men; and high, defined as 360 kcal per session for womenand 600 kcal per session for men74. The location of your fat makes a difference to your health. Weiss EP, et al. National Library of Medicine We recommend that prospective studies using representative populations are carried out to address the need for BMI category-specific waist circumference thresholds across different ethnicities (such as those proposed in Table, Disease prevention, Obesity, Metabolic syndrome, Predictive markers. In this prospective cohort study, the cohort was divided into quintiles for both BMI and waist circumference. During an experiment, I measured the Body Mass Index (BMI) and body fat percentage of adolescent girls. is funded by a Foundation Grant (Funding Reference Number FDN-167278) from the Canadian Institutes of Health Research. Pencina MJ, et al. sharing sensitive information, make sure youre on a federal Eastwood SV, et al. Each major is a level in that case). All Rights Reserved. In this short article, we introduce the different types of biological variables. For studies wherein the negative energy balance is induced by diet alone, evidence from RCTs suggest that waist circumference is reduced independent of diet composition and duration of treatment88. There are techniques for handling missing data, but these are beyond the scope of this course. Barzin M, et al. The key summary statistics for ordinal variables are relative frequencies and cumulative relative frequencies. We argue that BMI alone is not sufficient to properly assess or manage the cardiometabolic risk associated with increased adiposity in adults and provide a thorough review of the evidence that will empower health practitioners and professional societies to routinely include waist circumference in the evaluation and management of patients with overweight or obesity. Prevalence of childhood and adult obesity in the United States, 20112012. I.J.N. In 2009, Harpreet Bajaj and colleagues compared the prognostic performance of theArdern waist circumference values (Table1) with the traditional waist circumference values (men >102cm; women >88cm) for all-cause mortality in a large cohort of 5,453 predominantly white adults with high cardiometabolic risk111. Int J Obes (Lond). Mason C, Katzmarzyk PT. Estimated BMI-related medical expenditures, children and adults. In both sexes, the use of BMI category-specific waist circumference thresholds improved the identification of individuals at a high risk of future coronary events, leading the authors to propose BMI-specific waist circumference values (Table1). Moreover, height is only marginally associated with waist circumference31. The mode is a useful summary statistic for a continuous variable. -, Ward ZJ, Long MW, Resch SC, Giles CM, Cradock AL, Gortmaker SL. Available evidence from RCTs suggests that exercise is associated with substantial reductions in waist circumference, independent of the quantity or intensity of exercise. Another type of discrete variable is when truly continuous variables are only measured at discrete intervals. The rightmost column contains the body mass index (BMI) computed using the height and weight measurements. Exercise and ectopic fat in type 2 diabetes: a systematic review and meta-analysis. made a substantial contribution to discussion of the content. government site. Moreover, VAT is an established marker of morbidity50,51 and mortality24,52. Bajaj HS, Brennan DM, Hoogwerf BJ, Doshi KB, Kashyap SR. Clinical utility of waist circumference in predicting all-cause mortality in a preventive cardiology clinic population: a PreCIS database study. "Ultimately, they have similar risks as people who carry lots of body fat and have a high BMI.". Notably, for a given BMI, Canadians had a larger waist circumference in 2007 compared with 1981. Ogden CL, Carroll MD, Kit BK, Flegal KM. But if you're from India, your risk of diabetes starts going up with a BMI of about 21 or 22.". It is possible that the health protective effect of a larger BMI for a given waist circumference is explained by an increased accumulation of subcutaneous adipose tissue in the lower body46. Development of health-related waist circumference thresholds within BMI categories. R.D.S. Waist circumference and waist/hip ratio in relation to all-cause mortality, cancer and sleep apnea. Indeed, we argue that, at any BMI value, waist circumference is a major driver of the deterioration incardiometabolic risk markers or factors and, consequently, that reducing waist circumference is a critical step towards reducing cardiometabolic disease risk. Of particular interest to practitioners, several reviews have observed significant VAT reduction in response to exercise in the absence of weight loss80,85. A new index of abdominal adiposity as an indicator of risk for cardiovascular disease. By and large, both discrete and continuous variable can be qualitative and quantitative. 5. The data values for these ten participants are shown in the table below. Kahan specializes in helping people manage excess weight that can lead to health problems, including diabetes and heart disease. Calculated from a person's height and weight, BMI breaks down into four categories: "Probably for 90% or 95% of the population, BMI is just fine as a general measure of obesity," says Richard L. Atkinson, MD, a researcher and editor of the International Journal of Obesity. For practitioners, the decision to include a novel measure in clinical practice is driven in large part by two important, yet very different questions. Waist size: For an accurate measurement, the tape measure should go around your waist at the top of your hip bones in your lower back and go around to the belly button. But some critics take a different view. Diastolic blood pressures <80 mm Hg are considered normal, and we can see that the last two exceed the upper limit just barely. The natural course of healthy obesity over 20 years. Cook NR. and Y.M.) Exclusive Lifestyle, Nutrition & Health Advice. Carmienke S, et al. reports receiving fees for consulting and serving on the advisory board from Boehringer Ingelheim/Lilly Alliance and AMRA Medical and a research grant from Novo Nordisk. To simplify the formulas for sample statistics (and for population parameters), we usually denote the variable of interest as "X". Ross R, Hudson R, Stotz PJ, Lam M. Effects of exercise amount and intensity on abdominal obesity and glucose tolerance in obese adults: a randomized trial. Their blood sugar is excellent. Upon careful review of the various protocols described within the literature, the panel recommended that the waist circumference protocol described by the WHO guidelines98 (the midpoint between the lower border of the rib cage and the iliac crest) and the NIH guidelines99 (thesuperior border of the iliac crest) are probably more reliable and feasible measures for both the practitioner and the general public. For this same sample, the median is 71. "They have very low levels of muscle and bone -- often elderly people, those in poor shape, sometimes those who are sick. So what other tools can you use besides BMI? A note on the most widely used distribution and how to test for normality in R. What is the difference between population and sample? Savings in Medical Expenditures Associated with Reductions in Body Mass Index Among US Adults with Obesity, by Diabetes Status. Another 10% are widowed, 6% are single, and 1% are separated. 8600 Rockville Pike The reasons for that aren't totally clear, but it may have to do with having reserves to draw on when fighting off an illness. There is structured and unstructured data. Recall that categorical variables are those with two or more distinct responses that are unordered. To help prevent health problems from being overweight, men should keep their waist size to no more than 40 inches. The researchers found that although each measure was individually associated (BMI: HR 1.04, 95% CI 1.021.07; waist circumference: HR 1.11, 95% CI 1.091.13 per 1 SD increase) with increased risk of atherosclerotic CVD, no significant improvement occurred in the c-statistic with the addition of either BMI or waist circumference to the other PCE variables64. Table 2 - Frequency Distribution Table for Treatment with Antihypertensive Medication, Note in the table above that there are only n=3,532 valid responses, although the sample size was n=3,539. Example Scatterplot. Prevalence of overweight, obesity, and extreme obesity among adults aged 20 and over: United States, 19601962 through 20112014. Ethnicity-specific values for waist circumference that have been optimized for the identification of adultswith elevated CVD risk have been developed (Table2). As always, if you have a question or a suggestion related to the topic covered in this article, please add it as a comment so other readers can benefit from the discussion. . (Sorry, this is how REAL science works.) People of Indian descent face higher health risks at relatively lower BMIs, Atkinson says. "Their cholesterol and blood pressure are excellent. Kay SJ, Fiatarone Singh MA. In growing children and adolescents, the waistheight ratio could be more useful for the classification of abdominal obesity than waist circumference alone. Zhang C, Rexrode KM, van Dam RM, Li TY, Hu FB. Indeed, decades of research have produced unequivocal evidence that waist circumference provides both independent and additive information to BMI for morbidity and mortality prediction. The table below is a frequency distribution table for the ordinal blood pressure variable. LO 4.2: Classify a given variable as nominal, ordinal, discrete, or continuous. the binary outcomes and a Gaussian family and an identity link for the continuous outcome [33]. But as it turns out, BMI alone may not be the best way to size up your shape. FOIA Video: Types of Variables (3 Parts; 13:25 total time) Variables can be broadly classified into one of two types: Quantitative Categorical Results: Since BMI is only based on your height and weight, it is too simplistic a measure to determine your health. However, few studies have compared measures at the sites recommended by the WHO and NIH. Discrete (aka integer variables): represent counts and usually can't be divided into units smaller than one (e.g. http://creativecommons.org/licenses/by/4.0/, http://www.myhealthywaist.org/evaluating-cmr/clinical-tools/waist-circumference-measurement-guidelines/index.html. Inactivity, exercise, and visceral fat. In 2008, a panel of experts performed a systematic review of 120 studies to determine whether measurement protocol influenced the relationship between waist circumference, morbidity and mortality, and observed similar patterns of association between the outcomes and all waist circumference protocols across sample size, sex, age and ethnicity97. Browning LM, Hsieh SD, Ashwell M. A systematic review of waist-to-height ratio as a screening tool for the prediction of cardiovascular disease and diabetes: 0.5 could be a suitable global boundary value. Continuous (aka ratio variables): represent measures and can usually be divided into units smaller than one (e.g. Diabetes Care. R.R., I.J.N., I.S., J.S., P.M., R.D.S., B.A., A.C., F.B.H., B.A.G., A.Z., P.B., J.-C.F., R.H.E., Y.M. Again, there is clear order in these levels so health is in this case a qualitative ordinal variable. Effect of exercise training intensity on abdominal visceral fat and body composition. However, later evidence indicated that, compared with the WHR, waist circumference alone was more strongly associated with the absolute amount of intra-abdominal or visceral fat, the fat depot that conveys the strongest health risk23,24. 2023 May 19;9(5):e16210. 2019;381(25):24402450. Consequently, the combination of WHR and BMI for assessing obesity risk were replaced by single threshold values for waist circumference alone25. S.Y. For instance, a researcher may assign the number 1 to women and the number 2 to men (or 0 to the answer No and 1 to the answer Yes). Obesity is a major public health problem worldwide2 and reliance on measurements of BMI alone has proven inadequate to help clinicians assess and manage obesity-related health risk in their patients. Available from: Ward ZJ, Bleich SN, Cradock AL, Barrett JL, Giles CM, Flax C, et al.. The range in high-risk waist circumference values for both adult men (8098cm) and women (8096cm) varies considerably across ethnicities, which confirms the need for ethnicity-specific waist circumference values. Simulation of Growth Trajectories of Childhood Obesity into Adulthood. F.B.H. The rightmost column contains the body mass index (BMI) computed using the height and weight measurements. The numerical classification is only used to facilitate data collection and data management. Predicting CHD risk in France: a pooled analysis of the D.E.S.I.R., three city, PRIME, and SU.VI.MAX studies. The upper and lower body fat accumulation phenotypes were based on body morphology asassessed by external anthropometric measures such as skinfolds and circumferences. STRRIDE: a randomized controlled study. In summary, when associations between waist circumference and BMI with morbidity and mortality are considered in continuous models, for a given waist circumference, the higher the BMI the lower the adverse health risk. This characteristic alone is insufficient, however, as many novel biomarkers meet this minimum standard yet do not meaningfully improve risk prediction beyond traditional markers. Moreover, for all examples, the number of possibilities is finite. In summary, current evidence suggests that increasing the intensity of exercise interventions is not associated with a further decrease in waist circumference. The raw BMI is a quantitative continuous variable but the categorization of the BMI makes the transformed variable a qualitative (ordinal) variable, where the levels are in this case underweighted < normal < overweighted. Below we provide a more formal method to determine when values are extreme and thus when the median should be used. Reproduction in whole or in part without permission is prohibited. Accuracy of self-reported waist and hip measurements in 4492 EPIC-Oxford participants. For each of the other continuous variables, there are 10 distinct values and thus there is no mode, since no value appears more frequently than any other. Like the mean, the sample range can be affected by extreme values and thus it must be interpreted with caution. The emergence of waist circumference as a strong independent marker of morbidity and mortality is striking given that there is no consensus regarding the optimal protocol for measurement of waist circumference. World Health Organisation. Despite a strong association between waist circumference and BMI at the population level, emerging evidence suggests that, across populations, waist circumference might be increasing beyond what is expected according to BMI. With dichotomous variables the relative frequencies are often expressed as percentages (by multiplying by 100). When BMI and waist circumference are considered as continuous variables in the same risk prediction model, waist circumference remains a positive predictor of risk of death, but BMI is unrelated or negatively related to this risk. doi: 10.1016/j.heliyon.2023.e16210. Thus, for a given waist circumference, a larger BMI might represent a phenotype with elevations in lower body subcutaneous adipose tissue. Their observations are consistent with those of Slentz and colleagues, whereby differences in exercise intensity did not affect waist circumference reductions. The combination of BMI and waist circumference identifies a high-risk obesity phenotype better than either measure alone. A dose-response relation between aerobic exercise and visceral fat reduction: systematic review of clinical trials. 2). Pischon T, Boeing H, Hoffmann K, Bergmann M. General and abdominal adiposity and risk of death in Europe. wrote the article. Interested in statistics, R, and making them accessible to everyone. However, waist circumference is now clearly established as a key driver of altered levels of cardiometabolic risk factors and markers. Eckel N, Meidtner K, Kalle-Uhlmann T, Stefan N, Schulze MB. out of DrWeil.com subscriptions at any time. Subcutaneous fat loss is greater than visceral fat loss with diet and exercise, weight-loss promoting drugs and bariatric surgery: a critical review and meta-analysis. In 1956, Jean Vague was the firstto show the importance of fat distribution in relation tovarious diseases, describing what he termed android and gynoid types of obesity17. Similar to previous research, the optimal waist circumference thresholds increased across BMI categories in both ethnic groups and were higher in men than in women. Ford ES, Maynard LM, Li C. Trends in mean waist circumference and abdominal obesity among US adults, 19992012. Higher health care costs are associated with excess body weight across a broad range of ages and BMI levels, and are especially high for people with severe obesity. The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). Vague J. Go to: Abstract Identification and description of variables used in any study is a necessary component in biomedical research. Bigaard J, Spanggaard I, Thomsen BL, Overvad K, Tjonneland A. Self-reported and technician-measured waist circumferences differ in middle-aged men and women. However, no significant differences were observed in VAT reduction by single slice CT between high-intensity and low-intensity groups. In contrast, many African-Americans may have a high BMI, but without the health risks that usually go along with it. Of note, these sex-specific thresholds were originally developed using cross-sectional data in white adults, among whom a waist circumference of 102cm in men and 88cm in women corresponded to a BMI of 30.0kg/m2, which is the BMI threshold for obesity109. Their BMI shows up pretty high, and yet their body fat is actually pretty low," Kahan says. Specifically, when BMI and waist circumference are considered as categorical variables in the same risk prediction model, they are both positively related to morbidity and mortality38. Whatever the number of children in a family, it will never be 3.58 or 7.912 so the number of possibilities is a finite number and thus countable. This observation was confirmed by Sophie Eastwood and colleagues, who reported that in South Asian adults the protective effects of total subcutaneous adipose tissue for T2DM and HbA1c levels emerge only after accounting for visceral adipose tissue (VAT) accumulation48. Comparisons of waist circumferences measured at 4 sites. Waist circumference and all-cause mortality in a large US cohort. Quantifying importance of major risk factors for coronary heart disease. Gaps in our knowledge still remain, and refinement of waist circumference threshold values for a given BMI category across different ages, by sex and by ethnicity will require further investigation. Amankwah N, et al. Levels of circulating thyroid hormones provide the basis for classifying patients for diagnosis and therapy. PhD candidate and teaching assistant in statistics at UCLouvain. the contents by NLM or the National Institutes of Health. When reporting summary statistics for a continuous variable, the convention is to report one more decimal place than the number of decimal places measured. However, commonly used cost estimates are not sensitive to changes in weight across the entire body mass index (BMI) distribution as they are often based on discrete BMI categories. Janssen I, Katzmarzyk PT, Ross R. Body mass index is inversely related to mortality in older people after adjustment for waist circumference. The site is secure. Privacy Policy. Comparison of various surrogate obesity indicators as predictors of cardiovascular mortality in four European populations. Obes Rev. Why the association between waist circumference and adverse health risk is increased following adjustment for BMI is not established. Alberti KG, Zimmet P, Shaw J. Ross and colleagues controlled the amount of energy expenditure between moderate-intensity (50% VO2peak, n=76) and high-intensity (75% VO2peak, n=76) exercise groups74. And yet on every level that we look at, their health is actually quite good," he says. Usually, a basic descriptive analysis (and knowledge about the variables which have been measured) prior to the main statistical analyses is enough to check that all variable types are correct. General and abdominal obesity parameters and their combination in relation to mortality: a systematic review and meta-regression analysis. Larger sample sizes produce more precise results and therefore carry more weight. Although the waist circumference values that optimized prediction of the risk of death for any given BMI value were not reported, the findings reinforce the notion that waist circumference thresholds increase across BMI categories and that the combination of waist circumference and BMI provide improved predictions of health risk than either anthropometric measure alone. On the other hand, finding the mode of a continuous variable does not really make any sense because most of the time there will not be two exact same values, so there will be no mode. However, the researchers did not fix the level of exercise between the intensity groups, which might explain their observations. Hsieh SD, Yoshinaga H. Waist/height ratio as a simple and useful predictor of coronary heart disease risk factors in women. The one that is most familiar is the sample mean, which is computed by summing all of the values and dividing by the sample size. Abdominal adiposity in U.S. adults: prevalence and trends, 19602000. Epub 2023 Apr 8. However, all intervention groups significantly reduced waist circumference (~5cm) compared with the control arm (P<0.001)74. However, commonly used cost estimates are not sensitive to changes in weight across the entire body mass index (BMI) distribution as they are often based on discrete BMI categories. Years given (for example, 19992011) indicate the years in which data were collected. Your body type: Are you an apple shape or a pear shape? The cumulative relative frequencies are very useful for summarizing ordinal variables and indicate the proportion (between 0-1) or percentage (between 0%-100%) of patients at a particular level or below. or Healthy Lifestyle Brands. American Association of Clinical Endocrinologists and American College of Endocrinology comprehensive clinical practice guidelines for medical care of patients with obesity. The novel continuous outcome logistic regression model can be viewed as a generalization of the above-introduced models from discrete to continuous outcomes. They don't seem to have any health effects associated with their excess weight.". The two graphs below summarize BMI (Body Mass Index) measurements in four categories, i.e., younger and older men and women. When this process becomes saturated or in situations where adipose tissue has a limited ability to expand, there is a spillover of the excess energy, which must be stored in visceral adipose tissue as well as in normally lean organs such as the skeletal muscle, the liver, the pancreas and the heart, a process described as ectopic fat deposition. Questions to Ask Your Doctor. Evidence in support of adjusting waist circumference for BMI comes from Janne Bigaard and colleagues who report that a strong association exists between waist circumference and all-cause mortality after adjustment for BMI43. Federal government websites often end in .gov or .mil. Abdominal obesity index as an alternative central obesity measurement during a physical examination. also has patents issued with Fujirebio and Kyowa Medex Co., Ltd. issued. This observation is seemingly independent of age, sex and ethnicity, as few groups failed to demonstrate the general trend of secular waist circumference increasing beyond that expected by BMI (Fig.

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