Development and Application of the Remote Food Photography Method to Measure Food Intake in Exclusively Milk Fed Infants: A Laboratory-Based Study

Accurate methods of assessing food intake in infants are needed to assess the relationship between infant feeding practices and risk of childhood obesity. Current methods are either subjective or have limited ability for use beyond clinical research settings. To assess the accuracy of the RFPM to evaluate simulated milk intake including energy, macronutrient, and micronutrient intake compared to direct weighing within a controlled study. Individuals were recruited to prepare three 2 fl oz, 4 fl oz, 6 fl oz, and 8 fl oz servings of infant formula and to capture photographs at different stages of preparation (dry powdered formula, prepared formula, and liquid waste) using the SmartIntake® application. Gram weights of the bottles were obtained by the RFPM and direct weighing. Using the United States Department of Agriculture National Nutrient Database for Standard Reference, energy, macronutrient, and micronutrient values were generated from gram weights. Intake of formula prepared from powder measured by the RFPM was equivalent to weighed intake within 7.5% equivalence bounds among all servings and each serving size. The mean difference between methods varied among servings sizes with the RFPM underestimating intake by 1.6 ± 0.4 kcals in 2 fl oz servings, 4.8 ± 0.6 kcals in 4 fl oz servings, and 6.2 ± 1.0 kcals in 6 fl oz servings, and overestimating intake by 0.1 ± 1.2 kcals in 8 fl oz servings. Bland-Altman analysis showed that the RFPM overestimated intake at lower levels food intake and underestimated intake at higher levels. Considering photographs of only the prepared formula bottle and the bottle with formula waste to simulate ready-to-feed formula and human breast milk, intake estimated by the RFPM was equivalent to the directly weighed intake within 7.5% for all servings. The RFPM has higher accuracy than subjective methods and similar accuracy as compared to the objective methods in estimating simulated intake of milk and formula with lower burden to caregivers. The RFPM is a viable method for measuring intake in exclusively milk fed infants by caregivers in a controlled environment with potential for widespread use in research and clinical practice.