Photo-based calorie-tracking apps may underestimate energy in meals
Study examining four AI-powered apps found that calories and fat content were underestimated by roughly one-third
National Harbor, Md. (July 25, 2026) — Thanks to advances in AI, popular calorie-tracking apps can now use a photo of a meal to estimate the nutritional content of what you’re eating. Although these apps are convenient, a new study found that four photo-based apps underestimated the calories and fat content of meals by about a third.
Photo-based calorie tracking uses AI image recognition to identify foods in a meal photo and estimate portion sizes. This information is then compared with nutrition databases to calculate estimated calories and nutrients.
“Photo-based calorie tracking apps are very popular, especially for people trying to manage their health or lose weight,” said Aaron Hengist, a postdoctoral visiting fellow with the Intramural Program of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. “However, the accuracy of many of these apps has not been thoroughly evaluated. Our study helps address this question by looking at whether these apps can reliably estimate calories.”
Olivia Charles, a postbaccalaureate intramural research training fellow at NIDDK, will present the findings at NUTRITION 2026, the flagship annual meeting of the American Society for Nutrition, held July 25–28 in National Harbor, Maryland, just outside Washington, D.C.
The new research is part of a larger diet study at the NIH Clinical Center examining how the body processes nutrients when a person eats a low-carbohydrate (ketogenic) or standard diet. Meals for this clinical trial are prepared in a controlled metabolic kitchen, a type of research kitchen where ingredients are carefully weighed to the nearest 0.1 gram.
To evaluate how well photo-based calorie-tracking apps estimate nutritional content from images, the researchers acquired standardized photos of 102 meals prepared as part of the diet study and then ran them through the MyFitnessPal, LoseIt!, CalAI and Appediet apps.
“By using meals prepared in a tightly controlled metabolic kitchen, we were able to compare the apps’ estimates against a precise reference,” said Hengist. “This kind of direct, high-quality comparison hasn’t been available before.”
All four apps underestimated the calorie content of meals by about 250 to 345 calories, on average, and fat by about 30 grams. The analysis also showed that the MyFitnessPal and LoseIt! apps estimated the energy content of higher-calorie meals more accurately than lower-calorie meals and that all four apps estimated carbohydrates more consistently than other macronutrients.
“People using a photo-based tracking app without adjusting the portions or entering the amounts of food should take the results with a grain of salt,” said Hengist. “These apps tend to underestimate calories, especially from fats, so what they actually ate is likely higher than what the app shows.”
After performing the initial analysis, the researchers examined more than 200 additional meals to better understand what might affect the accuracy of the apps. Their early results suggest that the apps struggle more with meals that are part of a low-carb ketogenic diet, likely because the higher fat content of these meals tends to be consistently underestimated.
The investigators say that combining photo-based features with more traditional methods of measuring diet quality could improve the real-world accuracy of calorie-tracking apps.
Charles will present this research at 4:42 – 4:54 p.m. EDT on Saturday, July 25, during the President's Oral Session in the Gaylord National Resort & Convention Center (abstract; presentation details).
Please note that abstracts presented at NUTRITION 2026 were evaluated and selected by a committee of experts but have not generally undergone the same peer review process required for publication in a scientific journal. As such, the findings presented should be considered preliminary until a peer-reviewed publication is available.
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About NUTRITION 2026
NUTRITION 2026 is the flagship meeting of the American Society for Nutrition and the premier educational event for nutritional professionals around the globe. NUTRITION brings together lab scientists, practicing clinicians, population health researchers and community intervention investigators to identify solutions to today’s greatest nutrition challenges. The meeting also attracts rising leaders in the field, including undergraduate, graduate and medical students. NUTRITION 2026 will be held July 25–28 in National Harbor, Maryland, just outside Washington, D.C. https://nutrition.org/meeting/ #Nutrition2026
About the American Society for Nutrition (ASN)
ASN is the preeminent professional organization for nutrition research scientists and clinicians around the world. Founded in 1928, the society brings together the top nutrition researchers, medical practitioners, policy makers and industry leaders to advance knowledge and application of nutrition. ASN publishes four peer-reviewed journals and provides education and professional development opportunities to advance nutrition research, practice, and education. Since 2018, the American Society for Nutrition has presented NUTRITION, the leading global annual meeting for nutrition professionals. http://www.nutrition.org
Find more news briefs from NUTRITION 2026 at: https://www.eurekalert.org/newsroom/nutrition2026.
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