Evaluating the Validity of the PortionSize Smartphone Application for Estimating Dietary Intake in Free-Living Conditions: A Pilot Study

Objective: Evaluate the validity of the PortionSize application. Methods: In this pilot study, 14 adults used PortionSize to record their free-living food intake over 3 consecutive days. Digital photography was the criterion measure, and the main outcomes were estimated intake of food (grams), energy (kilocalories), and food groups. Equivalence tests with 25% equivalence bounds and Bland-Altman analysis were performed. Results: Estimated gram intake from PortionSize was equivalent (P P < 0.001) to digital photography estimates. PortionSize and digital photography estimated energy intake, however, were not equivalent (P P = 0.08), with larger estimates from PortionSize. In addition, PortionSize and digital photography were equivalent for vegetable intake (P P = 0.01), but PortionSize had larger estimates of fruits, grains, dairy, and protein intake (P P > 0.07; error range 11% to 23%). Conclusions and Implications: Compared with digital photography, PortionSize accurately estimated food intake and had reasonable error rates for other nutrients; however, it overestimated energy intake, indicating further application improvements are needed for free-living conditions.