Energy Expenditure in Free-Living Physical Activities and Sedentary Behaviors in Mexican Schoolchildren

Purpose: Metabolic equivalents for youth (METy) are derived using the estimated basal metabolic rate (BMR). However, is unknown whether this METy can be different when measured resting energy expenditure (REE) is used. The purposes of this article are to: (a) To determine whether there is equivalence between METy values calculated using measured REE (METy-mea) and METy using predicted BMR (METy-est). (b) To determine whether METy values of different activities are dependent on age, sex, and body composition. Methods: A cross-sectional study with a sample of 122 Mexican children (5-11 years old) was conducted. With indirect calorimetry, energy expenditure was measured at rest and during 16 sedentary- to vigorous-intensity physical activities. METy were obtained in two forms: METy-mea and METy-est. Equivalence testing was used to compare METy-mea and METy-est. To examine the individual-level agreement, Bland-Altman plots were graphed, and intra-class correlation coefficients (ICC) were calculated. Linear regression models were estimated having METy as the outcome. Results: For 15 activities, there was equivalence between METy-mea and METy-est (t > 2.05, p < 0.050). However, at the individual-level, for 7 activities the agreement between METy-eREE and METy-mREE was inadequate (ICC<0.75). In the Bland-Altman plots was evident that in 8 activities METy-est was biased compared to METy-mea, METy-est had more correlations with body mass index and body fat. Conclusions: In conclusion, at group-level, for most activities METy-mea and METy-est were equivalent. However, at the individual level, METy-est of many activities is not a valid estimate of METy-mea. METy-est of many physical activities were dependent on adiposity, which could be an artifact introduced when BMR is predicted.