katch-mcardle-bmr/dist/calculate-katch-mcardle-bmr.js

Function for calculating basal metabolic rate the Katch-McArdle way.

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = calculateKatchMcArdleBmr;

var _isNumber = require('is-number');

var _isNumber2 = _interopRequireDefault(_isNumber);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

function isPositiveNumber(num) {
  return (0, _isNumber2.default)(num) && num > 0;
}

function positiveNumberErrorMessage(parameter) {
  return 'The Katch-McArdle formula requires ' + parameter + ' to be a positive number.';
}

function calculateKatchMcArdleBmr() {
  var _ref = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {},
      weight = _ref.weight,
      bodyFatPercentage = _ref.bodyFatPercentage,
      _ref$useImperial = _ref.useImperial,
      useImperial = _ref$useImperial === undefined ? true : _ref$useImperial;

  if (!isPositiveNumber(weight)) {
    throw new Error(positiveNumberErrorMessage('weight'));
  }
  if (!isPositiveNumber(bodyFatPercentage)) {
    throw new Error(positiveNumberErrorMessage('body fat percentage'));
  }
  if (bodyFatPercentage > 100) {
    throw new Error('The body fat percentage can\'t be greater than 100.');
  }

  var base = 370;
  var leanMultiplier = 21.6;

  // If the body fat is greater than 1, adjust to a decimal value.
  if (bodyFatPercentage > 1) {
    bodyFatPercentage = bodyFatPercentage / 100;
  }

  var weightInKg = useImperial ? weight * 0.453592 : weight;
  var bodyFatMass = weightInKg * bodyFatPercentage;
  var leanMass = weightInKg - bodyFatMass;
  return base + leanMultiplier * leanMass;
}