New paper on estimating food intake from body weight

 Am J Clin Nutr. 2011 Jul;94(1):66-74. Epub 2011 May 11.

Estimating changes in free-living energy intake and its confidence interval.

Hall KD, Chow CC.

Laboratory of Biological Modeling, National Institute of Diabetes and Digestive
and Kidney Diseases, Bethesda, MD.

Background: Free-living energy intake in humans is notoriously difficult to
measure but is required to properly assess outpatient weight-control
interventions. Objective: Our objective was to develop a simple methodology that 
uses longitudinal body weight measurements to estimate changes in energy intake
and its 95% CI in individual subjects. Design: We showed how an energy balance
equation with 2 parameters can be derived from any mathematical model of human
metabolism. We solved the energy balance equation for changes in free-living
energy intake as a function of body weight and its rate of change. We tested the 
predicted changes in energy intake by using weight-loss data from controlled
inpatient feeding studies as well as simulated free-living data from a group of
"virtual study subjects" that included realistic fluctuations in body water and
day-to-day variations in energy intake. Results: Our method accurately predicted 
individual energy intake changes with the use of weight-loss data from controlled
inpatient feeding experiments. By applying the method to our simulated
free-living virtual study subjects, we showed that daily weight measurements over
periods >28 d were required to obtain accurate estimates of energy intake change 
with a 95% CI of <300 kcal/d. These estimates were relatively insensitive to
initial body composition or physical activity level. Conclusions: Frequent
measurements of body weight over extended time periods are required to precisely 
estimate changes in energy intake in free-living individuals. Such measurements
are feasible, relatively inexpensive, and can be used to estimate diet adherence 
during clinical weight-management programs.

PMCID: PMC3127505 [Available on 2012/7/1]
PMID: 21562087  [PubMed - in process]
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