Daniel P. Williams

Body fatness and risk for elevated blood pressure, total cholesterol, and serum lipoprotein ratios in children and adolescents.

BACKGROUND Recent studies have shown considerable variation in body fatness among children and adolescents defined as obese by a percentile rank for skinfold thickness. METHODS We examined the relationship between percent body fat and risk for elevated blood pressure, serum total cholesterol, and serum lipoprotein ratios in a biracial sample of 3320 children and adolescents aged 5 to 18 years. Equations developed specifically for children using the sum of subscapular (S) and triceps (T) skinfolds were used to estimate percent fat. The S/T ratio provided an index of trunkal fat patterning. RESULTS Significant overrepresentation (greater than 20%) of the uppermost quintile (UQ) for cardiovascular disease (CVD) risk factors was evident at or above 25% fat in males (32.2% to 37.3% in UQ) and at or above 30% fat in females (26.6% to 45.4% in UQ), even after adjusting for age, race, fasting status, and trunkal fat patterning. CONCLUSIONS These data support the concept of body fatness standards in White and Black children and adolescents as significant predictors of CVD risk factors. Potential applications of these obesity standards include epidemiologic surveys, pediatric health screenings, and youth fitness tests.

Prevalence of physical inactivity and recommended physical activity in community-based adults with mental retardation.

Little information has been reported on the leisure time physical activity (LTPA) habits of adults with mental retardation. Prevalence of physical inactivity and recommended LTPA of adults with mild to moderate mental retardation who live in community settings was described. Adults with mental retardation (76 men, 74 women) reported their physical activity habits. Overall, men and women who resided in community settings were similarly inactive, with 47% to 51% of individuals participating in little to no LTPA. Forty-two to 47% of them reported participation in moderate to vigorous LTPA five or more times per week. Limitations to quantifying physical activity through questionnaire process is discussed and development and implementation of programs designed to increase physical activity levels recommended.

Aging and body composition: biological changes and methodological issues.

There is no doubt that body composition changes with aging. Some general trends have been described, including an increase in body weight and fat mass in middle age followed by a decrease in stature, weight, FFM, and body cell mass at older ages. Losses in muscle, protein, and bone mineral contribute to the decline in FFM; however, the onset and rates of decline remain controversial. Most data are available for men and women < 80 yr and we know relatively little about the normal status and the changes that occur in body composition in elderly men and women. This situation has developed in part because the changes that occur in various body constituents with aging confound the estimation of body composition by traditional techniques. Hence, there is a need for longitudinal reference data in persons 80 yr of age, both to describe the normal status and to develop valid prediction equations for estimating body composition in older men and women in settings outside the laboratory. This should be possible using new technologies and approaches based on multiple component models of body composition. An understanding of the normal changes in body composition with increasing age, the normal variation in these changes, and their health implications is important for the health, nutritional support, and pharmacologic treatment of elderly men and women in the United States. The information is especially important because elderly men and women, in terms of both numbers and health care dollars, represent the most rapidly expanding segment of the U.S. population.

Differences in Cardiovascular Disease Risk between Nondiabetic Adults with Mental Retardation with and without Down Syndrome.

A reduced expression of the insulin resistance syndrome, a common neuroendocrine disorder underlying atherosclerosis, may play a role in reduced atherosclerosis in adults with Down syndrome. We compared selected components of the insulin resistance syndrome between 75 adults with Down syndrome and 70 with mental retardation due to other causes. After adjusting for age differences, residence, cigarette smoking, and medication use, women with Down syndrome had lower fasting plasma glucose and lower systolic blood pressure than comparison women. Men with Down syndrome had lower systolic and diastolic blood pressure than comparison men. Results suggest that women with Down syndrome may be less likely to express the insulin resistance syndrome, and men and women with Down syndrome may possess fewer atherosclerotic risk factors than the comparison groups.

Physical Activity, Dietary Intake, and the Insulin Resistance Syndrome in Nondiabetic Adults With Mental Retardation

The association between physical activity, dietary behaviors, and elevated cardiovascular disease risk factor components of the insulin resistance syndrome in adults with mental retardation was identified. Established clinical cutoff points were used to identify 145 participants with mild mental retardation and hyperinsulinemia, borderline high triglycerides, low high-density lipoprotein cholesterol, hypertension, and abdominal obesity. Odds ratios were calculated from logistic regression analysis. Those who participated in more frequent bouts of physical activity or who consumed lower dietary fat intakes were approximately one third as likely to have hyperinsulinemia and abdominal obesity compared to those who participated in less frequent physical activity or who consumed higher fat intakes, suggesting that these behaviors are protective against elevated components of the insulin resistance syndrome.

Percent Body Fat and Chronic Disease Risk Factors in U.S. Children and Youth

BACKGROUND The dramatic increase in pediatric obesity has renewed interest in accurate methods and screening indexes for identifying at-risk children and youth. Whether age-specific standards are needed is a factor that remains uncertain. PURPOSE This study was designed to describe the age-specific fatness-risk factor relationship in boys and girls across a wide age range. METHODS Data were from 12,279 white, black, and Mexican-American children and adolescents from the National Health and Nutritional Examination Surveys (NHANES) III (1998-1994) and IV (1999-2004). Children were grouped based on percent fat, estimated from subscapular and triceps skinfolds, and the age-specific relationships between percent fat and chronic disease risk factors (e.g., blood pressure, lipids and lipoprotein levels, glucose, insulin, and circulating C-reactive protein levels) were described in boys and girls, aged 6-18 years. RESULTS Percent fat was significantly related to risk factor levels. At higher levels of percent fat, the prevalence of adverse cardiovascular disease risk factors was higher, particularly above 20% fat in boys and above 30% fat in girls. In boys and girls, the interaction term age by percent fat was a significant predictor of risk factors, whereas the percent fat by race interaction term was nonsignificant. CONCLUSIONS The results demonstrate a strong relationship between chronic disease risk factors and percent fat in children and youth that varies by age in boys and girls.

Dietary intake of adults with mental retardation who reside in community settings.

The dietary intake of adults with mental retardation among three different community residential settings was described and compared. Two dietary screeners were administered to 325 adults. The womens Fruit and Vegetable Screener scores from group homes were significantly higher than scores from those with family members and in semi-independent settings. No significant differences were found in dietary intake across residences for men. Overall, 0% to 6% of the participants consumed the recommended 5 or more fruits and vegetables per day, and 15% to 30% consumed the recommended<or=30% or less of calories from fat. Results suggest that regardless of residential setting, men and women do not consume enough fruits and vegetables and consume too much dietary fat.

Estimation of body fat from skinfold thicknesses in middle-aged and older men and women: A multiple component approach

The relationship of skinfold thicknesses and body density to body fatness was assessed, and skinfold prediction equations were developed for the estimation of body fatness determined from measures of body density, total body water, and bone mineral in a sample of 91 males and 116 females aged 34–84 years. For a given skinfold thickness, adjustment for individual deviations in the water and bone mineral fractions of the fat‐free body assumed constant by traditional body composition models resulted in absolute reductions in overstimates of body fatness from 4.5 to 1.9% in females and from 2.8 to 1.7% in males for every 15 year increase in age. Percentage fat from density, water, and bone was estimated from skinfold thicknesses with SEEs of 2.9% in males and 3.8% in females. When compared to percentage fat from our multicomponent‐derived criterion, percentage fat from body density and a two‐component model resulted in individual errors ranging from underestimates of 5.6% fat to overestimates of 14.0% fat. The multicomponent prediction equations presented herein should produce more valid estimates of body composition in middle‐aged and older men and women than equations based on two‐component models.

Practical techniques for assessing body composition in middle-aged and older adults

The purpose of this study was to compare the relationships of anthropometric, bioelectrical impedance analysis (BIA), and near infrared interactance (NIR) measurements with a multiple-component (MC) criterion estimate of body composition derived from body density (D), body water (W), and bone mineral (B) in 48 white adults aged 49-80 yr. Relative errors of predicting the MC criterion from the practical measurements were determined by simple regressions within gender and calculated as the SEE divided by the criterion mean and expressed as a percentage. Relative errors were lowest for the BIA variable, height2/resistance (4.8-5.0%), higher for body mass index and the sum of 10 skinfold thicknesses (7.0-14.5%), and highest for NIR-derived optical density readings at the biceps and the sum of 10 sites (10.8-15.8%). Due to the low relative prediction error for height2/resistance, sex-specific BIA formulas for estimating fat-free mass from D, W, and B (FFM-DWB) were developed. The SEEs for predicting FFM-DWB from BIA, weight, and age were both 1.5 kg in women and men. Because BIA is not limited to ambulatory subjects, it is concluded that BIA may be a particularly useful, practical technique for estimating body composition in older adults.

Aqueous and mineral fractions of the fat-free body and their relation to body fat estimates in men and women aged 49-82 years.

Due to age-related decreases in bone minera11,2 and total body protein3 coupled with a possible increase in the hydration of the fat-free mass (1,1-M)4, it is likely that, on average, the density of the FFM is lower in older relative to younger adults. Other investigators have speculated that the density of the FFM may become more variable with advancing age5,6. In either case, erroneous estimates of body fat percentage (%Fat) will result when traditional two-component (2C: fat and fat-free) models7 are used in older adults. More complex four component (4C: fat, water, mineral and fat-free residual) models3,5,8 may provide more valid substitutes for the 2C model7 in older adults.