Can We Estimate Calories with a Photograph?

When it comes to smartphones, you can accomplish just about anything with the push of a button. Everything from recipes to diet advice, you can find it all in the App Store. Soon to be added to that list is a new calorie-counting application: PlateMate.

Harvard engineering students developed PlateMate, software that uses crowd-sourcing to estimate calories of a food or meal based on a photograph. Although it has yet to make it to a mobile app, the creators see that in its future. With PlateMate, you take a photo of your food, submit it, and within a short period of time you receive an estimate of total calories. Other applications have used trained dietitians to estimate this number, but with PlateMate, the estimate comes from five complete amateurs via Amazon Mechanical Turk, the idea being that it taps into the “wisdom of crowds.” In preliminary testing the creators of the application found that it achieved similar results to that of trained dietitians in estimating calories.

As a dietitian, I question the effectiveness of this type of application. Rarely does a person sit down for a meal and eat foods with only one ingredient. For example, does your turkey sandwich have low-fat cheese or regular cheese? What about the latte you order every morning — is it non-fat or full-fat? Is your soup made with heavy cream? The answers to all of these questions will affect both the nutrients found in the foods and the total calories. Without a trained dietitian looking at the photograph and/or asking the appropriate questions, how could PlateMate possibly be accurate?

However, put the application accuracy aside and allow me to point out the obvious: registered dietitians are nutrition experts, not calorie counters. Yes, I am a dietitian and, naturally, I will have a biased view, but when you talk about a wholesome diet and/or losing weight, there is so much more to it than counting calories. Your overall nutrition intake — everything from vitamins and minerals to protein and carbohydrates — all play a key role in keeping you healthy. PlateMate is very limited in its ability to provide feedback on other aspects of the diet. Calories are only part of that picture (pun intended).

The creators of PlateMate list cost as one of the driving factors behind developing this app, citing the high cost of using a trained dietitian to estimate calories based on photographs. They also report that other calorie counting and/or dieting applications are cumbersome and time-consuming. Even if both are the case, a PlateMate user must keep in mind that even if it might come close to the accurate calorie amount, it is still completely inappropriate for overall diet analysis.