Validation of an inexpensive and accurate mathematical method to measure long-term changes in free-living energy intake

Am J Clin Nutr. 2015 Aug;102(2):353-8. doi: 10.3945/ajcn.115.111070. Epub 2015 Jun 3.


Background: Accurate measurement of free-living energy intake (EI) over long periods is imperative for understanding obesity and its treatment. Unfortunately, traditional methods rely on self-report and are notoriously inaccurate. Although EI can be indirectly estimated by the intake-balance method, this technique is prohibitively labor-intensive and expensive, requiring repeated measures of energy expenditure via doubly labeled water (DLW) along with multiple dual-energy X-ray absorptiometry (DXA) scans to measure changes in body energy stores.

Objective: Our objective was to validate a mathematical method to measure long-term changes in free-living energy intake.

Design: We measured body weight and EI changes (ΔEI) over 4 time intervals by using the intake-balance method in 140 individuals who underwent 2 y of caloric restriction as part of the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy study. We compared the ΔEI values calculated by using DLW/DXA with those obtained by using a mathematical model of human metabolism whose only inputs were the initial demographic information and repeated body weight data.

Results: The mean ΔEI values calculated by the model were within 40 kcal/d of the DLW/DXA method throughout the 2-y study. For individual subjects, the overall root mean square deviation between the model and DLW/DXA method was 215 kcal/d, and most of the model-calculated ΔEI values were within 132 kcal/d of the DLW/DXA method.

Conclusions: Accurate and inexpensive estimates of ΔEI that are comparable to the DLW/DXA method can be obtained by using a mathematical model and repeated body weight measurements.

Trial registration: NCT00427193.

Keywords: caloric restriction; dietary assessment; energy balance; energy intake; mathematical modeling; weight loss.

Publication types

  • Clinical Trial
  • Research Support, N.I.H., Extramural
  • Validation Study

MeSH terms

  • Adult
  • Algorithms
  • Body Mass Index
  • Body Weight
  • Caloric Restriction
  • Diet, Reducing*
  • Energy Intake*
  • Energy Metabolism
  • Female
  • Humans
  • Male
  • Middle Aged
  • Models, Biological*
  • National Institute of Diabetes and Digestive and Kidney Diseases (U.S.)
  • Nutrition Assessment*
  • Overweight / diet therapy*
  • Overweight / metabolism
  • Reproducibility of Results
  • United States
  • Weight Loss*
  • Young Adult

Associated data