- Email: [email protected]
Global trends in body-mass index
Correspondence
*Erlend T Aasheim, Torgeir T Søvik [email protected] Imperial Weight Centre, Imperial College London, London SW6 8RF, UK (ETA); and Department of Gastrointestinal Surgery, Oslo University Hospital Aker, Oslo, Norway (TTS) 1
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Finucane MM, Stevens GA, Cowan MJ, et al. National, regional, and global trends in body-mass index since 1980: systematic analysis of health examination surveys and epidemiological studies with 960 country-years and 9·1 million participants. Lancet 2011; 377: 557–67. Whitlock G, Lewington S, Sherliker P, et al. Body-mass index and cause-specific mortality in 900 000 adults: collaborative analyses of 57 prospective studies. Lancet 2009; 373: 1083–96. Sturm R. Increases in morbid obesity in the USA: 2000-2005. Public Health 2007; 121: 492–96. Flegal KM, Carroll MD, Ogden CL, Curtin LR. Prevalence and trends in obesity among US adults, 1999-2008. JAMA 2010; 303: 235–41. Flum DR, Belle SH, King WC, et al. Perioperative safety in the longitudinal assessment of bariatric surgery. N Engl J Med 2009; 361: 445–54.
Mariel Finucane and colleagues1 provide important information about the alarming trends of increasing body-mass index (BMI) worldwide and highlight the effect of this development on the growing incidence of cardiovascular disease and type 2 diabetes. Additionally, they discuss the often low effectiveness of interventions to combat obesity and its metabolic consequences. Hence, to use the limited resources available in the most effective way, we need to identify who, for a given BMI, is at the highest risk of metabolic diseases. In this respect, we and others have found that about 25–30% of obese people might not be at increased risk of metabolic diseases.2,3 Consequently, we can identify people who are obese but remain insulin sensitive and have a reduced intima-media thickness of the carotid arteries (an early marker of atherosclerosis). Prospective studies have confirmed that the risk of allcause, cancer, and cardiovasculardisease mortality is not higher in metabolically healthy obese people than it is in non-obese individuals.4,5 What characterises this interesting phenotype? By use of precise metabolic imaging with magnetic resonance techniques, we found that decreased www.thelancet.com Vol 377 June 4, 2011
visceral fat mass, but, more importantly, lower ectopic fat accumulation in the skeletal muscle and predominantly in the liver, determined whether a metabolically benign or malign obesity is present.2 Certainly, such measurements could not be applied feasibly for routine diagnostic purposes; however, health-care professionals could perhaps focus not only on BMI but also on waist circumference, and particularly the presence of fatty liver, by use of more simple markers, when dealing with the problem of obesity. NS is supported by a Heisenberg-Grant of the Deutsche Forschungsgemeinschaft (STE 1096/1-1). We declare that we have no conflicts of interest.
*Norbert Stefan, Konstantinos Kantartzis, Jürgen Machann, Fritz Schick, Hans-Ulrich Häring [email protected] Department of Internal Medicine (NS, KK, H-UH) and Section of Experimental Radiology (JM, FS), University of Tübingen, 72076 Tübingen, Germany 1
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Finucane MM, Stevens GA, Cowan MJ, et al. National, regional, and global trends in body-mass index since 1980: systematic analysis of health examination surveys and epidemiological studies with 960 countryyears and 9·1 million participants. Lancet 2011; 377: 557–67. Stefan N, Kantartzis K, Machann J, et al. Identification and characterization of metabolically benign obesity in humans. Arch Intern Med 2008; 168: 1609–16. Wildman RP, Muntner P, Reynolds K, et al. The obese without cardiometabolic risk factor clustering and the normal weight with cardiometabolic risk factor clustering: prevalence and correlates of 2 phenotypes among the US population (NHANES 1999–2004). Arch Intern Med 2008; 168: 1617–24. Meigs JB, Wilson PW, Fox CS, et al. Body mass index, metabolic syndrome, and risk of type 2 diabetes or cardiovascular disease. J Clin Endocrinol Metab 2006; 91: 2906–12. Calori G, Lattuada G, Piemonti L, et al. Prevalence, metabolic features, and prognosis of metabolically healthy obese Italian individuals: the Cremona Study. Diabetes Care 2011; 34: 210–15.
Authors’ reply Estimates for diseases and risk factors at the national level have a range of applications (eg, in global benchmarking) but, by design, do not apply to subgroups, which might be based on socioeconomic status or geography.1,2 Although subgroup analysis would provide insight into within-country
disparities, doing subgroup analysis by socioeconomic status globally and over time is hindered by the incomparability of measures of socioeconomic status over time and across countries.3 Additionally, such an analysis would have to formally model the heterogeneities of the association between socioeconomic status and body-mass index (BMI) by region, national income, and time. Even if consistent and comparable estimates of BMI by socioeconomic status find a positive association in some lowincome countries, the association might attenuate or reverse with rising national income,4 as was the case for tobacco smoking. Finally, the absolute risk associated with raised BMI might be higher among groups with low socioeconomic status for two reasons: first, they have a higher background risk of disease owing to exposure to other risks and restricted access to health care;1,2 and second, they have lower access to treatment for the mediators of hazardous effects such as diabetes, high blood pressure, and high cholesterol. For all these reasons, curbing the global obesity epidemic, and those of the associated metabolic risk factors, with implementation taking into account within-country variations and disparities, will help to achieve both the aggregate and disparity benefits of prevention.1,2 Estimates of the full distribution of BMI, including the prevalence of extreme obesity, would indeed be valuable for understanding whether the rise in mean BMI is simply due to a distributional shift or whether there is an increase in the spread and skewness of the distribution. This issue is partly reflected (for all obesity) in figure 4 of our paper,5 and is a subject of continuing methodological and empirical research by the collaborating group. Novel markers of adiposity and obesity should also be pursued, although their application to population-based surveillance will 1917
*Erlend T Aasheim, Torgeir T Søvik [email protected] Imperial Weight Centre, Imperial College London, London SW6 8RF, UK (ETA); and Department of Gastrointestinal Surgery, Oslo University Hospital Aker, Oslo, Norway (TTS) 1
2
3
4
5
Finucane MM, Stevens GA, Cowan MJ, et al. National, regional, and global trends in body-mass index since 1980: systematic analysis of health examination surveys and epidemiological studies with 960 country-years and 9·1 million participants. Lancet 2011; 377: 557–67. Whitlock G, Lewington S, Sherliker P, et al. Body-mass index and cause-specific mortality in 900 000 adults: collaborative analyses of 57 prospective studies. Lancet 2009; 373: 1083–96. Sturm R. Increases in morbid obesity in the USA: 2000-2005. Public Health 2007; 121: 492–96. Flegal KM, Carroll MD, Ogden CL, Curtin LR. Prevalence and trends in obesity among US adults, 1999-2008. JAMA 2010; 303: 235–41. Flum DR, Belle SH, King WC, et al. Perioperative safety in the longitudinal assessment of bariatric surgery. N Engl J Med 2009; 361: 445–54.
Mariel Finucane and colleagues1 provide important information about the alarming trends of increasing body-mass index (BMI) worldwide and highlight the effect of this development on the growing incidence of cardiovascular disease and type 2 diabetes. Additionally, they discuss the often low effectiveness of interventions to combat obesity and its metabolic consequences. Hence, to use the limited resources available in the most effective way, we need to identify who, for a given BMI, is at the highest risk of metabolic diseases. In this respect, we and others have found that about 25–30% of obese people might not be at increased risk of metabolic diseases.2,3 Consequently, we can identify people who are obese but remain insulin sensitive and have a reduced intima-media thickness of the carotid arteries (an early marker of atherosclerosis). Prospective studies have confirmed that the risk of allcause, cancer, and cardiovasculardisease mortality is not higher in metabolically healthy obese people than it is in non-obese individuals.4,5 What characterises this interesting phenotype? By use of precise metabolic imaging with magnetic resonance techniques, we found that decreased www.thelancet.com Vol 377 June 4, 2011
visceral fat mass, but, more importantly, lower ectopic fat accumulation in the skeletal muscle and predominantly in the liver, determined whether a metabolically benign or malign obesity is present.2 Certainly, such measurements could not be applied feasibly for routine diagnostic purposes; however, health-care professionals could perhaps focus not only on BMI but also on waist circumference, and particularly the presence of fatty liver, by use of more simple markers, when dealing with the problem of obesity. NS is supported by a Heisenberg-Grant of the Deutsche Forschungsgemeinschaft (STE 1096/1-1). We declare that we have no conflicts of interest.
*Norbert Stefan, Konstantinos Kantartzis, Jürgen Machann, Fritz Schick, Hans-Ulrich Häring [email protected] Department of Internal Medicine (NS, KK, H-UH) and Section of Experimental Radiology (JM, FS), University of Tübingen, 72076 Tübingen, Germany 1
2
3
4
5
Finucane MM, Stevens GA, Cowan MJ, et al. National, regional, and global trends in body-mass index since 1980: systematic analysis of health examination surveys and epidemiological studies with 960 countryyears and 9·1 million participants. Lancet 2011; 377: 557–67. Stefan N, Kantartzis K, Machann J, et al. Identification and characterization of metabolically benign obesity in humans. Arch Intern Med 2008; 168: 1609–16. Wildman RP, Muntner P, Reynolds K, et al. The obese without cardiometabolic risk factor clustering and the normal weight with cardiometabolic risk factor clustering: prevalence and correlates of 2 phenotypes among the US population (NHANES 1999–2004). Arch Intern Med 2008; 168: 1617–24. Meigs JB, Wilson PW, Fox CS, et al. Body mass index, metabolic syndrome, and risk of type 2 diabetes or cardiovascular disease. J Clin Endocrinol Metab 2006; 91: 2906–12. Calori G, Lattuada G, Piemonti L, et al. Prevalence, metabolic features, and prognosis of metabolically healthy obese Italian individuals: the Cremona Study. Diabetes Care 2011; 34: 210–15.
Authors’ reply Estimates for diseases and risk factors at the national level have a range of applications (eg, in global benchmarking) but, by design, do not apply to subgroups, which might be based on socioeconomic status or geography.1,2 Although subgroup analysis would provide insight into within-country
disparities, doing subgroup analysis by socioeconomic status globally and over time is hindered by the incomparability of measures of socioeconomic status over time and across countries.3 Additionally, such an analysis would have to formally model the heterogeneities of the association between socioeconomic status and body-mass index (BMI) by region, national income, and time. Even if consistent and comparable estimates of BMI by socioeconomic status find a positive association in some lowincome countries, the association might attenuate or reverse with rising national income,4 as was the case for tobacco smoking. Finally, the absolute risk associated with raised BMI might be higher among groups with low socioeconomic status for two reasons: first, they have a higher background risk of disease owing to exposure to other risks and restricted access to health care;1,2 and second, they have lower access to treatment for the mediators of hazardous effects such as diabetes, high blood pressure, and high cholesterol. For all these reasons, curbing the global obesity epidemic, and those of the associated metabolic risk factors, with implementation taking into account within-country variations and disparities, will help to achieve both the aggregate and disparity benefits of prevention.1,2 Estimates of the full distribution of BMI, including the prevalence of extreme obesity, would indeed be valuable for understanding whether the rise in mean BMI is simply due to a distributional shift or whether there is an increase in the spread and skewness of the distribution. This issue is partly reflected (for all obesity) in figure 4 of our paper,5 and is a subject of continuing methodological and empirical research by the collaborating group. Novel markers of adiposity and obesity should also be pursued, although their application to population-based surveillance will 1917