title: Calculating the metabolizable energy of macronutrients: a critical review of Atwater's results.
abstract: The current values for metabolizable energy of macronutrients were proposed in 1910. Since then, however, efforts to revise these values have been practically absent, creating a crucial need to carry out a critical analysis of the experimental methodology and results that form the basis of these values. Presented here is an exhaustive analysis of Atwater's work on this topic, showing evidence of considerable weaknesses that compromise the validity of his results. These weaknesses include the following: (1) the doubtful representativeness of Atwater's subjects, their activity patterns, and their diets; (2) the extremely short duration of the experiments; (3) the uncertainty about which fecal and urinary excretions contain the residues of each ingested food; (4) the uncertainty about whether or not the required nitrogen balance in individuals was reached during experiments; (5) the numerous experiments carried out without valid preliminary experiments; (6) the imprecision affecting Atwater's experimental measurements; and (7) the numerous assumptions and approximations, along with the lack of information, characterizing Atwater's studies. This review presents specific guidelines for establishing new experimental procedures to estimate more precise and/or more accurate values for the metabolizable energy of macronutrients. The importance of estimating these values in light of their possible dependence on certain nutritional parameters and/or physical activity patterns of individuals is emphasized. The use of more precise values would allow better management of the current overweight and obesity epidemic.
authors.affiliation: M.J. Sánchez-Peña, A.C. Ramírez-Anguiano, S.F. Velasco-Ramírez, and L.J. González-Ortiz are with the Chemistry Department, University Center of Exact Sciences and Engineering, University of Guadalajara, Guadalajara, Jalisco, Mexico. F. Márquez-Sandoval is with the Department of Human Reproduction, Child Growth and Development, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico. G. Macedo-Ojeda is with the Department of Public Health, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico.
authors.forename: M Judith
authors.initials: MJ
authors.lastname: Sánchez-Peña
authors.affiliation: M.J. Sánchez-Peña, A.C. Ramírez-Anguiano, S.F. Velasco-Ramírez, and L.J. González-Ortiz are with the Chemistry Department, University Center of Exact Sciences and Engineering, University of Guadalajara, Guadalajara, Jalisco, Mexico. F. Márquez-Sandoval is with the Department of Human Reproduction, Child Growth and Development, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico. G. Macedo-Ojeda is with the Department of Public Health, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico.
authors.forename: Fabiola
authors.initials: F
authors.lastname: Márquez-Sandoval
authors.affiliation: M.J. Sánchez-Peña, A.C. Ramírez-Anguiano, S.F. Velasco-Ramírez, and L.J. González-Ortiz are with the Chemistry Department, University Center of Exact Sciences and Engineering, University of Guadalajara, Guadalajara, Jalisco, Mexico. F. Márquez-Sandoval is with the Department of Human Reproduction, Child Growth and Development, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico. G. Macedo-Ojeda is with the Department of Public Health, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico.
authors.forename: Ana C
authors.initials: AC
authors.lastname: Ramírez-Anguiano
authors.affiliation: M.J. Sánchez-Peña, A.C. Ramírez-Anguiano, S.F. Velasco-Ramírez, and L.J. González-Ortiz are with the Chemistry Department, University Center of Exact Sciences and Engineering, University of Guadalajara, Guadalajara, Jalisco, Mexico. F. Márquez-Sandoval is with the Department of Human Reproduction, Child Growth and Development, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico. G. Macedo-Ojeda is with the Department of Public Health, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico.
authors.forename: Sandra F
authors.initials: SF
authors.lastname: Velasco-Ramírez
authors.affiliation: M.J. Sánchez-Peña, A.C. Ramírez-Anguiano, S.F. Velasco-Ramírez, and L.J. González-Ortiz are with the Chemistry Department, University Center of Exact Sciences and Engineering, University of Guadalajara, Guadalajara, Jalisco, Mexico. F. Márquez-Sandoval is with the Department of Human Reproduction, Child Growth and Development, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico. G. Macedo-Ojeda is with the Department of Public Health, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Macedo-Ojeda
authors.affiliation: M.J. Sánchez-Peña, A.C. Ramírez-Anguiano, S.F. Velasco-Ramírez, and L.J. González-Ortiz are with the Chemistry Department, University Center of Exact Sciences and Engineering, University of Guadalajara, Guadalajara, Jalisco, Mexico. F. Márquez-Sandoval is with the Department of Human Reproduction, Child Growth and Development, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico. G. Macedo-Ojeda is with the Department of Public Health, University Center of Health Sciences, University of Guadalajara, Guadalajara, Jalisco, Mexico. ljglez@yahoo.com.mx.
authors.forename: Luis J
authors.initials: LJ
authors.lastname: González-Ortiz
mesh_terms: D004032:Diet; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage / Q000652:urine; D004734:Energy Metabolism; D017408:Guidelines as Topic; D006801:Humans; D008962:Models, Theoretical; D015596:Nutrition Assessment; D012107:Research Design
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins