April 12, 2006
FAMILY MEALS FOCUS #11
Interpreting the news and research about feeding and eating

Interpreting the obesity data

Based on National Health and Nutrition Examination Survey (NHANES) data, the 2003-2004 incidence of overweight and obesity increased for children and adults 2 to >60 years, with the exception of >20 year old women.¹ Releasing the findings generated the usual dire warnings and calls for intervention. This issue of Family Meals Focus explains what the data means from the perspective of normal growth and weight patterns. FMF #12 will consider how to take action without doing harm.

Remember, health risks of overweight and obesity are low BMI,body density, tracks from the child to the adult; body fatness does not.² Despite strong beliefs about health consequences of overweight, high BMI in childhood is not associated with increased risk of cardiovascular disease later in life.^2,3 Mortality for adults is lower at BMI 25 to 30 than in the "normal" weight category of 18.5 to 25. The lowest life expectancies are at BMI <18.5, followed by BMI >35.⁴

Distinguish semantics from reality While BMI is widely used as a proxy for body fat, it is actually a measure of body density. CDC guidelines define children as at risk for overweight or overweight when BMI on the CDC growth charts plots at or above the 85th or 95th percentiles, respectively. Adults are defined as being overweight, obese and extremely obese when BMI is >25, >30 and >40, respectively. For adults, BMI 25 is statistically average, BMI 30 is between the 75th and 85th percentiles.⁵

Distinguish normal from abnormal With some current skewing to the upper ends, BMI is normally distributed along the same bell-shaped curve as other biological parameters. Five percent of children normally plot at the 95th percentile and above, 15% at the 85th percentile and above. Defining those normally large children as overweight or at risk for overweight is spurious.⁶ However, more children than statistically expected,a still-concerning balance of 17% and 12%,plot at those levels.¹ At some point, their weight has accelerated to cross percentiles. Evidence-based clinical observations show abnormal weight acceleration to be an outgrowth of distorted feeding dynamics.

Don't jump to conclusions about 2-to-6 year olds There were only 402 2-to-6 year olds in the sample: 119 whites, 125 blacks and 111 Mexican-Americans.¹ While this data will undoubtedly be used to heighten alarm and put pressure on early intervention, the authors state clearly that numbers are too small to reach statistical significance.

Remember, Mexican-Americans have naturally higher body density Mexican-American children are naturally shorter and heavier and have a mean BMI at the 85th percentile.⁷ At age 2 to 5 years, incidence of BMI >85th percentile for non-Hispanic whites, non-Hispanic blacks and Mexican-Americans was 25.0, 24.0 and 32.6 percent, respectively. Gaps between ethnic groups narrowed at later ages.¹

For more information for about health risks of overweight and normal growth, see Your Child's Weight: Helping Without Harming.

Reference List

1. Ogden CL, Carroll MD, Curtin LR, McDowell MA, Tabak CJ, Flegal KM. Prevalence of Overweight and Obesity in the United States, 1999-2004. JAMA. 2006;295:1549-1555.

2. Wright CM, Parker L, Lamont D, Craft AW. Implications of childhood obesity for adult health: findings from thousand families cohort study. British Medical Journal. 2001;323(7324):1280-1284.

3. Lawlor DA, Martin RM, Gunnell D, et al. Association of body mass index measured in childhood, adolescence, and young adulthood with risk of ischemic heart disease and stroke: findings from 3 historical cohort studies. Am J Clin Nutr. 2006;83:767-773.

4. Flegal KM, Graubard BI, Williamson DF, Gail MH. Excess Deaths Associated With Underweight, Overweight, and Obesity. JAMA. 2005;293:1861-1867.

5. Najjar MF, Rowland M; Anthropometric reference data and prevalence of overweight, United States, 1976-80. Vital and Health Statistics, National Center for Health Statistics. Washington, D.C.: U.S. Government Printing Office; 1987;Series 11: No. 238; DHHS Pub. No. (PHS) 87-1688.

6. Satter EM; Chapter 10, Understand Your Child's Growth. Your Child's Weight: Helping Without Harming. Madison, WI: Kelcy Press; 2005:323-380 .

7. Ryan AS, Martinez GA, Roche AF. An evaluation of the association between socioeconomic status and the growth of American children: Data from the Hispanic Health and Nutrition Examination Survey--NHANES 1982-1984. American Journal of Clinical Nutrition. 1990;51:944S-952S.

Family Meals Focus by Ellyn Satter, MS, RD, LCSW, BCD. discusses trends, research and clinical issues in eating and feeding and interprets other research from a feeding-dynamics, eating-competence perspective. For past issues of Family Meals Focus, click here.

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