R/bmr.R

In nutrition: Useful Functions for People on a Diet

#' @title Basal Metabolic Rate
#' @description Estimates the basal metabolic rate of a person.
#' @param weight weight, in kilograms
#' @param age age, in years
#' @param fat fat proportion in body
#' @param height height, in centimeters
#' @param activity activity level (a scalar between 1 and 2)
#' @param method calculation method ("msj" for Mifflin-St. Jeor or "kma" for
#'  Katch-McArdle)
#' @param gender "male" or "female"
#' @return The Basal Metabolic Rate, in kilocalories
#' @author Waldir Leoncio
#' @references
#' https://www.calculator.net/bmr-calculator.html
#'
#' Mifflin, M. D., St Jeor, S. T., Hill, L. A., Scott, B. J., Daugherty, S. A.,
#' & Koh, Y. O. (1990). A new predictive equation for resting energy expenditure
#' in healthy individuals. The American journal of clinical nutrition, 51(2),
#' 241-247.
#'
#' McArdle, W. D., Katch, F. I., & Katch, V. L. (2010). Exercise physiology:
#' nutrition, energy, and human performance. Lippincott Williams & Wilkins.
#' @export
#' @examples bmr(67, 40, .12, 178) # for an individual with 12% body fat
bmr <- function(weight, age, fat, height, activity = 1.45, method = "msj", gender = "male") {
  msj_constant <- switch(
    gender,
    "male" = 5,
    "female" = -161,
    stop("invalid gender for calculation")

  )
  bmr <- switch(
    method,
    "msj" = 9.99 * weight + 6.25 * height - 4.92 * age + msj_constant,
    "kma" = 370 + 21.6 * (1 - fat) * weight,
    stop("method must be either msj or kma")
  )
  return(bmr * activity)
}