# child_weight: Dynamic Children Weight Change Model In bw: Dynamic Body Weight Models for Children and Adults

## Description

Estimates weight given age, sex, fat mass, and fat free mass,

## Usage

 1 2 3 4 child_weight(age, sex, FM = child_reference_FFMandFM(age, sex)$FM, FFM = child_reference_FFMandFM(age, sex)$FFM, EI = NA, richardsonparams = list(K = NA, Q = NA, B = NA, A = NA, nu = NA, C = NA), days = 365, dt = 1, checkValues = TRUE) 

## Arguments

 age (vector) Age of individual (yrs) sex (vector) Sex either "female" or "male" FM (vector) Fat Mass at Baseline FFM (vector) Fat Free Mass at Baseline EI (matrix) Numeric Matrix with energy intake richardsonparams (list) List of parameters for Richardson's curve for energy. See details. Optional days (numeric) Days to run the model. dt (double) Time step for Rungue-Kutta method checkValues (boolean) Checks whether values of fat mass and free fat mass are possible

## Details

richardsonparams is a named list of parameters: K, A, Q, C, B, nu which result in Richardon's curve:

A + \frac{K-A}{(C + Q exp(-B*t))^{1/nu}}

The Richardson's curve is another option for modelling the energy intake for a child: by specifying the parameters no energy input is needed; instead Energy is assumed to follow the equation:

EI(t) = A + \frac{K-A}{(C + Q exp(-B*t))^{1/nu}}

## Author(s)

Rodrigo Zepeda-Tello rzepeda17@gmail.com

Dalia Camacho-García-Formentí daliaf172@gmail.com

## References

Hall, K. D., Butte, N. F., Swinburn, B. A., & Chow, C. C. (2013). Dynamics of childhood growth and obesity: development and validation of a quantitative mathematical model. The Lancet Diabetes & Endocrinology, 1(2), 97-105.

Haschke, F. (1989). Body Composition During Adolescence. Body Composition Measurements in Infants and Children. Ross Laboratories Columbus, OH, 76–83.

Fomon, Samuel J, Ferdinand Haschke, Ekhard E Ziegler, and Steven E Nelson. 1982. Body Composition of Reference Children from Birth to Age 10 Years. The American Journal of Clinical Nutrition 35 (5). Am Soc Nutrition: 1169–75.

Ellis, Kenneth J, Roman J Shypailo, Steven A Abrams, and William W Wong. 2000. The Reference Child and Adolescent Models of Body Composition: A Contemporary Comparison. Annals of the New York Academy of Sciences 904 (1). Wiley Online Library: 374–82.

Deurenberg, Paul, Jan A Weststrate, and Jaap C Seidell. 1991. Body Mass Index as a Measure of Body Fatness: Age-and Sex-Specific Prediction Formulas. British Journal of Nutrition 65 (2). Cambridge University Press: 105–14.

Katan, Martijn B, Janne C De Ruyter, Lothar DJ Kuijper, Carson C Chow, Kevin D Hall, and Margreet R Olthof. 2016. Impact of Masked Replacement of Sugar-Sweetened with Sugar-Free Beverages on Body Weight Increases with Initial Bmi: Secondary Analysis of Data from an 18 Month Double–Blind Trial in Children. PloS One 11 (7). Public Library of Science: e0159771.

@adult_weight for the weight change model for adults; model_plot for plotting the results and model_mean for aggregate data estimation.
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 #EXAMPLE 1: INDIVIDUAL MODELLING #-------------------------------------------------------- #For one child with default energy intake child_weight(6,"male") #For a child with specific energy intake child_weight(6,"male",2.5, 16, as.matrix(rep(2000, 365)), days = 365) #Using Richardson's energy girl <- child_weight(6,"female", days=365, dt = 5, richardsonparams = list(K = 2700, Q = 10, B = 12, A = 3, nu = 4, C = 1)) plot(girl\$Body_Weight[1,]) #EXAMPLE 2: DATASET MODELLING #-------------------------------------------------------- #Antropometric data FatFree <- c(32, 17.2, 18.8, 20, 24.1) Fat <- c(4.30, 2.02, 3.07, 1.12, 2.93) ages <- c(10, 6.2, 5.4, 4, 4.1) sexes <- c("male", "female", "female", "male", "male") #With specific energy intake eintake <- matrix(rep(2000, 365*5), ncol = 5) #Returns a weight change matrix and other matrices model_weight <- child_weight(ages, sexes, Fat, FatFree, eintake) model_weight_2 <- child_weight(ages, sexes, Fat, FatFree, richardsonparams = list(K = 2700, Q = 10, B = 12, A = 3, nu = 4, C = 1))