Obese individuals do not underreport dietary intake to a greater extent than nonobese individuals when data are allometrically-scaled

Objective: The aim of this study was to assess the extent of misreporting in obese and non-obese adults on an absolute, ratio-scaled, and allometrically-scaled basis. Method: Self-reported daily energy intake (EI) was compared with total energy expenditure (TEE) in 221 adults (106 male,115 female; age 53±17 years, stature 1.68±0.09 m, mass 79.8±17.2 kg) who participated in a doubly-labelled water (DLW) subsection of 2013-2015 National Diet and Nutrition Survey. Data were log-transformed and expressed as absolute values, according to simple ratio-standards (per kg body mass) and adjusted for body mass allometrically. Absolute and ratio-scaled misreporting were examined using full-factorial General Linear Models with repeated measures of the natural logarithms of TEE or EI as the within-subjects factor. The natural logarithm of body mass was included as a covariate in the allometric method. The categorical variables of gender, age, obesity, and Physical Activity Level (PAL) were the between-factor variables. Results: On an absolute-basis, self-reported EI (2759±590 kcal·d-1) was significantly lower than TEE measured by DLW (2759±590 kcal·d-1: F1,205=598.81,p<0.001,ηp2=0.75). We identified significantly greater underreporting in individuals with an obese BMI (F1,205=29.01,p<0.001,ηp2=0.12), in more active individuals (PAL>1.75; F1,205=34.15, p<0.001, ηp2=0.14) and in younger individuals (<55 years; F1,205=14.82,p<0.001,ηp2=0.07), which are all categories with higher energy needs. Ratio-scaling data reduced the effect sizes. Allometric-scaling removed the effect of body mass (F1,205=0.02,p=0.887,ηp2=0.00). Conclusion: In weight-stable adults, obese individuals do not underreport dietary intake to a greater extent than non-obese individuals. These results contradict previous research demonstrating that obesity is associated with a greater degree of underreporting.