NCCOR members explore metrics to express children’s energy expenditure

Physical activity plays an important role in the fight against childhood obesity. Developing, testing, and evaluating individual and environmental interventions and policies designed to increase youth physical activity would be enhanced if there were a comparable metric for physical activity applicable to youth. Several approaches have been used to express energy expenditure in youth, but no consensus exists as to which best normalizes data for the wide range of ages and body sizes across a range of physical activities.

The National Collaborative on Childhood Obesity Research (NCCOR) convened a workgroup in 2012 to assist efforts to achieve consensus on methods and measurements for improving youth energy expenditure estimates. On June 24, workgroup members published, “Exploring Metrics to Express Energy Expenditure of Physical Activity in Youth,” which examined several common metrics for expressing energy expenditure to determine whether one metric can be used for all healthy children.

Researchers conducted a secondary analysis of oxygen uptake from 947 youth aged 5 to 18 who engaged in 14 different activities at five different sites. Resting metabolic heart rate was computed and absolute oxygen uptake, oxygen uptake per kilogram body mass, net oxygen uptake, allometric scaled oxygen uptake, and youth metabolic equivalents (YOUTH-MET or METy) were calculated. These metrics were then regressed with age, sex, height, and body mass.

The authors found four key findings on measuring youth energy expenditure:

  1. No energy expenditure metric completely eliminated the influence of age, physical characteristics, and sex.
  2. Adult metabolic equivalents (Adult MET) consistently overestimated energy expenditure.
  3. YOUTH-MET (METy) was better for expressing energy expenditure for sedentary and light activities.
  4. Allometric scaling was better for moderate and vigorous intensity activities.

Recognizing and accounting for its age-dependency, especially for more vigorous activities, the authors recommend the YOUTH-MET as the more feasible metric for improving of the Compendium of Physical Activities for Youth. “Age is a key factor related to energy expenditure for youth both at rest and during physical activity and should be accounted for in developing common metrics for various physical activities in children and adolescents,” the authors write. In addition, the authors note two additional issues that are not addressed in this study: translation and generalizability. Whether individuals will be able to calculate, interpret, and utilize a single, common metric is important and will need to be examined further.

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Citation: McMurray RG, Butte NF, Crouter SE, Trost SG, Pfeiffer KA, Bassett DR, et al. (2015) Exploring Metrics to Express Energy Expenditure of Physical Activity in Youth. PLoS ONE 10(6): e0130869. doi:10.1371/journal.pone.0130869

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