Correspondence
Guidelines for Healthy Weight
N Engl J Med 1999; 341:2097-2098December 30, 1999
- Article
To the Editor:
Willett et al. (Aug. 5 issue)1 have highlighted the importance of taking early action to prevent increases in measures of obesity and the associated risks, including type 2 diabetes, hypertension, and dyslipidemia. The data to which they refer, however, concern predominantly white populations and are not necessarily representative of other racial or ethnic groups.
Unlike the situation in many Western countries, the prevalence of obesity in Chinese populations remains relatively low. In Hong Kong, approximately 6 percent of the population have a body-mass index (the weight in kilograms divided by the square of the height in meters) of 30 or higher, although a third have a body-mass index of 25 or higher.2 Despite these relatively lower levels of obesity, the disorders associated with the metabolic syndrome are reaching epidemic proportions in Hong Kong.3 Ten percent of the adult population 25 to 74 years of age have type 2 diabetes (as determined on the basis of a 75-g oral glucose-tolerance test), 17 percent have hypertension (defined as a systolic blood pressure of 140 mm Hg or more and a diastolic blood pressure of 90 mm Hg or more), and more than 50 percent have dyslipidemia (defined as a total cholesterol level of 5.2 mmol per liter [200 mg per deciliter] or more and a triglyceride level of 2.0 mmol per liter [180 mg per deciliter] or more).2 However, we found that the mean body-mass index and measurements of waist circumference of patients with components of the metabolic syndrome fall near or under the cutoff used to define overweight in whites. Furthermore, when we investigated risk factors among Chinese persons in Hong Kong, the anthropometric levels associated with the lowest prevalence were in subjects with a body-mass index below 22 or a waist circumference below 70 cm.
It is apparent from our data that, for Chinese persons, the criteria for obesity should be lowered. Our patients should be encouraged to reduce their body-mass index below 22 and their waist circumference below 70 cm. It is important for clinicians to recognize that cutoff values in guidelines are inherently arbitrary and that those currently used for whites are inappropriately high for Asian patients, including Chinese. Such patients may be within the “normal” range for weight, but their risks of type 2 diabetes, hypertension, and dyslipidemia and the illnesses associated with these disorders are more than double those of persons at optimal weight levels.
3 ReferencesG. Neil Thomas, Ph.D.
Brian Tomlinson, M.D.
Julian A.J.H. Critchley, M.D., Ph.D.
Chinese University of Hong Kong, Shatin, Hong Kong, China1
Willett WC ,Dietz WH ,Colditz GA . Guidelines for healthy weight. N Engl J Med 1999;341:427-434
Full Text | Web of Science | Medline2
Janus ED . Epidemiology of cardiovascular risk factors in Hong Kong. Clin Exp Pharmacol Physiol 1997;24:987-988
CrossRef | Web of Science | Medline3
Chan JCN ,Cockram CS . Diabetes in the Chinese population and its implications for health care. Diabetes Care 1997;20:1785-1790
Web of Science | Medline
To the Editor:
Willett et al. endorse the use of the body-mass index because published studies demonstrate a fairly strong correlation between body-mass index and the results of hydrodensitometry or dual-energy x-ray absorptiometry. At our primary care clinic, we perform direct measurement of body fat using infrared interactance and bioelectrical impedance. We find that the measured percentage of body fat consistently correlates with body-mass index only in persons with a body-mass index of more than 35. As the body-mass index drops, the correlation becomes much weaker. Many people with a “normal” body-mass index have body-fat readings well into the range for obesity. More important, when interventions are introduced, measured body fat and body-mass index can travel in opposite directions. For example, one of our patients recently lost 20 lb (9 kg) by following a calorie-restricted diet only, but her body fat rose from 35 percent to over 40 percent. Virtually every pound she lost came from lean body mass. We believe that clinicians should use the available technology to measure the component that actually creates the risk — elevated body fat.
William L. Wilson, M.D.
Chisholm Medical Clinic, Chisholm, MN 55719To the Editor:
The body-mass index is helpful, since it translates the values on the height and weight charts into a single number. But the body-mass index does not discriminate between adipose tissue and muscle, and it may contain other systematic flaws.
Consider professional basketball players, hardly an overweight group. At 1.98 m and 95 kg, Michael Jordan has a body-mass index of 24, which falls in the upper end of the healthy-weight group, as stratified by the International Obesity Task Force, although his body fat is under 10 percent. Shaquille O'Neal's body fat is reported to be near 5 percent, but his dimensions (2.18 m and 141 kg) indicate that he is grossly overweight — nearly obese — on the scale of the International Obesity Task Force, with a body-mass index of 29.7. The Chicago Bulls drafted four rookies this year. Their body-mass indexes ranged from 27.3 to 29.8, perhaps another bad sign for season-ticket holders, but hardly a sign that these players are overweight.
The body-mass index needs a simple correction factor. Perhaps if one multiplied the body-mass index by the waist circumference fat stores could be discriminated from muscle mass and a simple, useful number could be generated. The index could be called the WHW index, for weight–height–waist. Alternatively, it could be called the BM-W index, a reminder of the connection between affluence and body fat. In the example above, Michael Jordan's body-mass index of 24 could be corrected by his waist circumference (0.88 m) to an index of 21. A fan 68 in. (1.73 m) tall weighing 72 kg would also have an uncorrected body-mass index of 24. But his 39-in. (0.99-m) waist means his corrected BM-W is 24, so this corrected index helps to discriminate the fit from the fat. Sadly, Shaq still comes in as overweight.
Gary J. Davis, M.D.
Evanston Hospital, Evanston, IL 60201Author/Editor Response
The authors reply:
To the Editor: We appreciate the data provided by Thomas et al. that reinforce our point that the upper limit of 25 for body-mass index typically used to define the cutoff of healthy weights is far from optimal for many persons. Determining whether the range of healthy weights is truly different for populations in Hong Kong and the United States requires more thorough population-based studies.
We also agree with Drs. Wilson and Davis that the body-mass index is an imperfect measure of body fat, mainly because it does not discriminate between muscle and fat mass. However, the body-mass index actually works quite well as a simple surrogate measure in most young and middle-aged adults, if one excludes persons who are trained athletes or who are involved in muscle-building programs. As we have noted elsewhere, the correlation between body-mass index and fat mass adjusted for height is approximately 0.9.1 Moreover, as we documented in our review,2 the body-mass index strongly predicts the risk of major health events, even within the range of 20 to 30. However, because of the limitations of the body-mass index, we suggested the use of the amount of weight gained since young adulthood (from about the age of 21 years in men and from several years younger in women). This simple measure will identify those at higher risk due to fat accumulation in midlife, even though many still have a body-mass index of less than 25. Bioelectric impedance may be helpful, but it, too, is not perfect and has not been shown to be clearly superior to simple measures of weight and height in a well population.
As Dr. Davis points out, waist circumference can be a useful ancillary measure. The index he proposes is one way to incorporate this information, but it needs further evaluation. The failure of this index to pass the “Shaq” test is a reminder that physicians should not forget to look at the patient and use clinical judgment when interpreting any measurement.
2 ReferencesWalter C. Willett, M.D., Dr.P.H.
Harvard School of Public HealthGraham Colditz, M.D., Dr.P.H.
Brigham and Women's Hospital, Boston, MA 02115William Dietz, M.D., Ph.D.
Centers for Disease Control and Prevention, Atlanta, GA 303411
Spiegelman D ,Willett WC ,Israel RG ,Bouchard C . Absolute fat mass, percent body fat, body-fat distribution: which is the real determinant of blood pressure and serum glucose? Am J Clin Nutr 1992;55:1033-1044
Web of Science | Medline2
Willett WC ,Dietz WH ,Colditz GA . Guidelines for healthy weight. N Engl J Med 1999;341:427-434
Full Text | Web of Science | Medline
- Citing Articles (5)
Citing Articles
1
Brian Tomlinson, Han Bing Deng, G Neil Thomas. (2008) Prevalence of obesity amongst Chinese populations revisited. Future Lipidology 3:2, 139-152
CrossRef2
G. Neil Thomas, Brian Tomlinson, Athena W. L. Hong, Stanley S. C. Hui. (2006) Age-related anthropometric remodelling resulting in increased and redistributed adiposity is associated with increases in the prevalence of cardiovascular risk factors in Chinese subjects. Diabetes/Metabolism Research and Reviews 22:1, 72-78
CrossRef3
G. Neil Thomas, Sai-Yin Ho, Edward D. Janus, Karen S.L. Lam, Anthony J. Hedley, Tai Hing Lam. (2005) The US National Cholesterol Education Programme Adult Treatment Panel III (NCEP ATP III) prevalence of the metabolic syndrome in a Chinese population. Diabetes Research and Clinical Practice 67:3, 251-257
CrossRef4
SHIVAKUMAR CHITTURI, GEOFFREY C FARRELL, JACOB GEORGE. (2004) Non-alcoholic steatohepatitis in the Asia-Pacific region: Future shock?. Journal of Gastroenterology and Hepatology 19:4, 368-374
CrossRef5
Wilson Y.S Leung, G Neil Thomas, Juliana C.N Chan, Brian Tomlinson. (2003) Weight management and current options in pharmacotherapy: Orlistat and sibutramine. Clinical Therapeutics 25:1, 58-80
CrossRef
