Take a picture of what you eat and you'll know how many calories you're taking in. That is how so-called calorie tracking apps are marketed.
The problem is that they seem to significantly underestimate the number of calories in a meal, according to a project in which nutrition researchers had four of the most popular apps calculate calories for more than 300 meals.
Preliminary results show that they underestimate calories by about 33 percent, which is between 250 and 345 calories per meal. The apps had particular difficulty evaluating fatty meals.
The project is part of a larger dietary study , which was presented at the American Society for Nutrition's annual meeting on Saturday.
