Measuring food intake with digital photography

Abstract

The digital photography of foods method accurately estimates the food intake of adults and children in cafeterias. When using this method, images of food selection and leftovers are quickly captured in the cafeteria. These images are later compared with images of 'standard' portions of food using computer software. The amount of food selected and discarded is estimated based upon this comparison, and the application automatically calculates energy and nutrient intake. In the present review, we describe this method, as well as a related method called the Remote Food Photography Method (RFPM), which relies on smartphones to estimate food intake in near real-time in free-living conditions. When using the RFPM, participants capture images of food selection and leftovers using a smartphone and these images are wirelessly transmitted in near real-time to a server for analysis. Because data are transferred and analysed in near real-time, the RFPM provides a platform for participants to quickly receive feedback about their food intake behaviour and to receive dietary recommendations for achieving weight loss and health promotion goals. The reliability and validity of measuring food intake with the RFPM in adults and children is also reviewed. In sum, the body of research reviewed demonstrates that digital imaging accurately estimates food intake in many environments and it has many advantages over other methods, including reduced participant burden, elimination of the need for participants to estimate portion size, and the incorporation of computer automation to improve the accuracy, efficiency and cost-effectiveness of the method.

Keywords: dietary assessment digital photography; energy intake; food intake; food photography; free-living.

Figure 1

Food intake is estimated with the Food Photography Application^© by comparing images of participants’ food selection (A) and leftovers (B) to an image containing a known amount of food (C) to estimate portion size. The application then automatically calculates the energy and nutrient content of food selection, leftovers, and food intake.

Figure 2

When using the RFPM, participants use a Smartphone to capture images of their food selection, leftovers, and a reference card. These images are then immediately sent to a server for analysis. Reprinted from Martin et al. (2012).

Figure 3

The RFPM uses Ecological Momentary Assessment (EMA) methods to improve data quality and minimize missing data. Prompts are automatically sent to participants’ Smartphones to remind them to capture images of their foods and to send these images to the research staff (the images are received by, and managed in, a computer program called the Food Photography Application^©). The Food Photography Application^© also stores responses to the prompts, and it sends automated reports to the research team and they can quickly identify when data acquisition problems occur. Reprinted from Martin et al. (2012).

Figure 4

Validity of the RFPM at measuring the energy intake of adults in free-living conditions and the energy and nutrient intake of adults during laboratory-based buffet meals. The gold standard comparison measures were: the doubly labeled water method for free-living conditions, and directly weighed foods during the buffet meals. Mean participant error is displayed and asterisks indicate that the RFPM estimate differed significantly from the gold standard (alpha = .05 for the comparison of free-living data and alpha = .01 for all other comparisons).

Figure 5

Bland and Altman analysis comparing energy intake (EI) estimated with the Remote Food Photography Method (RFPM) to the gold standard-EI measured with doubly labeled water (DLW). The RFPM’s error was similar across levels of EI. Reprinted from Martin et al. (2012).

Figure 6

Validity of the RFPM at measuring the food intake (g) of preschool-age children over 24-hours in the children’s natural environments, including their home and a Head Start center.