Predictive equations for fat mass in older Hispanic adults with excess adiposity using the 4-compartment model as a reference method.

BACKGROUND: Predictive equations are the best option for assessing fat mass in clinical practice due to their low cost and practicality. However, several factors, such as age, excess adiposity, and ethnicity can compromise the accuracy of the equations reported to date in the literature. OBJECTIVE: To develop and validate two predictive equations for estimating fat mass: one based exclusively on anthropometric variables, the other combining anthropometric and bioelectrical impedance variables using the 4C model as the reference method. SUBJECTS/METHODS: This is a cross-sectional study that included 386 Hispanic subjects aged ≥60 with excess adiposity. Fat mass and fat-free mass were measured by the 4C model as predictive variables. Age, sex, and certain anthropometric and bioelectrical impedance data were considered as potential predictor variables. To develop and to validate the equations, the multiple linear regression analysis, and cross-validation protocol were applied. RESULTS: Equation 1 included weight, sex, and BMI as predictor variables, while equation 2 considered sex, weight, height squared/resistance, and resistance as predictor variables. R2 and RMSE values were ≥0.79 and ≤3.45, respectively, in both equations. The differences in estimates of fat mass by equations 1 and 2 were 0.34 kg and -0.25 kg, respectively, compared to the 4C model. This bias was not significant (p < 0.05). CONCLUSIONS: The new predictive equations are reliable for estimating body composition and are interchangeable with the 4C model. Thus, they can be used in epidemiological and clinical studies, as well as in clinical practice, to estimate body composition in older Hispanic adults with excess adiposity.

Determination of Fat-Free Mass Density and its Components in Older Hispanic Adults by In Vivo Methods.

The densitometry method estimates body composition based on cadaver reference values, mainly the fat-free mass density value of 1.100 g/cm3. However, several changes in fat-free mass components by aging, ethnicity, and excess adiposity could influence their density and affect body composition estimations. The present study aimed to compare the mean fat-free mass component values in older Hispanic adults to cadaver reference values. This cross-sectional study included a sample of 420 subjects aged ≥60 yr from northern Mexico. Fat-free mass was determined by the four-compartment model using air displacement plethysmography, the deuterium dilution technique, and dual-energy X-ray absorptiometry for body density, aqueous and mineral fractions of body weight, respectively. A 1-sample t test was used to compare the fat-free mass density and aqueous, mineral, and residue fractions of fat-free mass from subjects in the study to the assumed cadaver reference values. The mean fat-free mass density value for the total sample of older Hispanic adults (1.096 ± 0.011 g/cm3) was significantly (p < 0.001) lower than the assumed value of 1.100 g/cm3, except in obese older men. The mean aqueous fraction of fat-free mass (74.8 ± 3.3%) was higher than the assumed value of 73.8%, and the mean residue fraction of fat-free mass value was lower (18.3 ± 3.4%) than the reference value of 19.4%. Indeed, only the mean mineral fraction of fat-free mass value (6.8 ± 0.8%) was similar to the reference value. In the total sample, all characteristic mean fat-free mass values in these older Hispanic adults differed from cadaver reference values, except the mineral fraction of fat-free mass value.

Agreement between laboratory methods and the 4-compartment model in assessing fat mass in obese older Hispanic-American adults.

BACKGROUND/OBJECTIVES: Densitometry (Siri's and Brozek's equations), hydrometry (by the deuterium dilution technique), and dual-energy X-ray absorptiometry (DXA) are three methods for estimating body composition. However, because they are all based on certain assumptions, they may not be applicable to aged and obese subjects due to changes in their body composition. Hence, the validity of these "laboratory methods" could be affected in obese older people. The main aim was to assess the agreement between densitometry, hydrometry, and DXA with the 4-compartment (4C) model to estimate fat mass (FM) in obese older Hispanic-American adults. As secondary goals, we explored whether the bias in densitometry and hydrometry results could be improved by modifying the assumptions regarding fat-free mass (FFM) density and hydration factor (HF) values, respectively. In the case of DXA, we explored the factors that contribute to bias. SUBJECTS/METHODS: This is a cross-sectional study based on a sample of 171 obese subjects aged ≥60 years from 3 regions of northern Mexico. Body composition was assessed by the 4C model as the reference method and by all three laboratory methods. Agreement of the latter with the 4C model was probed by Bland and Altman analysis, a paired sample t-test, and simple linear regression analyses. In addition, the mean FFM density estimated in this sample, and HF values (published previously) of 0.737 and 0.753 for obese older Hispanic-American men and women, respectively, were considered as ethnic- and gender-specific values. These values were used to modify the densitometric and hydrometric equations in order to improve their bias. Finally, we tested whether the hydration status and indirect markers of adiposity are contributing factors to the bias of DXA using multiple linear regression analysis. RESULTS: Siri's equation overestimated FM by 0.57 kg (p < 0.01), while Brozek's equation, hydrometry, and DXA underestimated it by 1.24 kg, 0.89 kg, and 0.79 kg (p < 0.01), respectively, compared to the 4C model. The bias in the densitometry and hydrometry results was eliminated by substituting the ethnic- and gender-specific values into the equations. Finally, we found that hip circumference contributes to the bias in DXA. CONCLUSION: The densitometry, hydrometry, and DXA methods are not interchangeable with the 4C model for assessing fat mass in obese, older Hispanic-American adults. The lack of agreement could indicate that the assumptions of each method do not apply to this population.

High Hydration Factor in Older Hispanic-American Adults: Possible Implications for Accurate Body Composition Estimates.

Age- and obesity-related body composition changes could influence the hydration factor (HF) and, as a result, body composition estimates derived from hydrometry. The aim of the present study was to compare the HF in older Hispanic-American adults to some published values. This cross-sectional study included a sample of 412 subjects, men and women, aged ≥60 years from northern Mexico. HF values were calculated based on the ratio of total body water-using the deuterium dilution technique-to fat-free mass, derived from the four-compartment model. The mean HF value for the total sample (0.748 ± 0.034) was statistically (p ≤ 0.01) higher than the traditionally assumed value of 0.732 derived from chemical analysis, the "grand mean'' value of 0.725 derived from in vivo methods, and the 0.734 value calculated for older French adults via the three-compartment model. The HF of the older women did not differ across the fat mass index categories, but in men the obese group was lower than the normal and excess fat groups. The hydration factor calculated for the total sample of older Hispanic-American people is higher than the HF values reported in the literature. Therefore, the indiscriminate use of these assumed values could produce inaccurate body composition estimates in older Hispanic-American people.

[Antineoplastic treatment impact on nutritional status in patients with breast cancer]. / Impacto del tratamiento antineoplásico en el estado nutricional en pacientes con cáncer de mama.

BACKGROUND: Breast cancer is the most commonly diagnosed malignancy in women in Mexico and also has the highest mortality. Although treatment has improved significantly, it can affect the nutritional status of the recipients. OBJECTIVE: The aim of this study was to assess the impact of the initial phase of antineoplastic therapy on the nutritional status in patients with breast cancer. METHODS: Forty subjects with primary diagnosed of invasive breast cancer were studied in a before and after intervention (six month apart) using a quasi-experimental design. Basal and six month after intervention measurements included were anthropometry, body composition by dual X-ray absorptiometry (DEXA), diet by 24-hour recall and food frequency questionnaire, as well as serum -carotene and retinol. The therapy effect was analyzed using repeated measurements mixed linear regression. RESULTS: Lean tissue decreased after the studied period (p=0.032). Addicionally, there was an interaction between weight, BMI and body fat parameters with menopausal status, increasing in these variables due to therapy only premenopausal patients (p=0.005, 0.006 and 0.001, respectively). Decreased serum retinol (p=0.049) despite the improvement in -carotene status (p=0.03). In general there was an increase the consumption of vegetables food products whilst a decrease in animal foods. CONCLUSION: The breast cancer antineoplastic treatment had a negative effect on weight and body fat, especially in young women. Although there were some positive dietary changes, vegetables consumption remained insufficient, which was also reflected in serum biomarkers.

Presentación: El cáncer de mama es el tipo de tumor más frecuentemente diagnosticado entre las mujeres de México y también el de más alta mortalidad. Aunque el tratamiento ha mejorado significativamente, puede afectar al estado nutricional del paciente. Objetivo: El objetivo de este estudio era evaluar el impacto de la fase inicial de la terapia antineoplásica sobre el estado nutricional en pacientes con cáncer de mama. Métodos: Cuarenta sujetos con diagnóstico primario de cáncer de mama invasivo fueron estudiados antes y después de la intervención (con seis meses de desfase) usando un diseño quasi-experimental. Las mediciones al inicio y seis meses después de la intervención incluyeron antropometría, composición corporal mediante absorciometría dual de rayos X (DEXA), cuestionario de recopilación de dieta en 24 horas y frecuencia de comidas, y suero beta-caroteno y retinol. El efecto de la terapia fue analizado empleando mediciones repetidas y regresión lineal mixta. Resultados: El tejido magro disminuyó tras el periodo de estudio (p=0.032). Además, se dio una interacción entre los parámetros de peso, IMC y grasa corporal con el estado de menopausia, aumentando en estas variables debido a la terapia solo en pacientes premenopáusicas (p=0.005, 0.006 y 0.001, respectivamente). Descenso de retinol sérico (p=0.049) a pesar de la mejoría en el estado de beta-caroteno (p=0.03). En general hubo un aumento en el consumo de verdura y un descenso de productos animales. Conclusión: El tratamiento antineoplásico del cáncer de mama tuvo un efecto negativo sobre el peso y la grasa corporal, especialmente en mujeres jóvenes. Aunque se observaron algunos cambios positivos en la dieta, el consumo de verdura siguió siendo insuficiente, lo que también se reflejó en los biomarcadores séricos.