Calorie-counting 'eButton' camera measures portion size

Those who are counting calories must rely on either clunky food scales or inaccurate guesses of portion sizes. But a new wearable computer called the eButton, which matches images against a library of 3D geometric shapes, may soon provide a stealthy, accurate way of measuring calories.

The eButton - which fastens to a shirt like an ordinary badge - consists of a low-power central processing unit (CPU), a random-access memory (RAM) communication interface and a Linux or Android operating system.

Researchers say that accurately counting calories with such a device could help with intervention of chronic conditions, such as obesity, diabetes and cardiovascular disease.

The device works like a fly on the wall, automatically taking pictures of the wearer's food and calculating calories. The creators say unlike camera-enabled cell phones, which are able to collect digital images of food only by intruding on normal life, the eButton is able to capture the images without interfering.

The researchers, who are from the University of Pittsburgh in partnership with researchers from China, studied the effectiveness of their eButton. The results were recently published online in the journal Measurement Science and Technology.

How the eButton works

In order to estimate food volume from a single image of food on a dining plate, the device uses three processes:

1. The food location is calculated using a coordinate system and the plate as a scale reference.


2. The food is "segmented" from the background in the image. Image features, such as color contrast, color similarity and curve bending degree are taken into account.


3. The 3D shape of the food (for example, an ellipse for a potato or a wedge for pizza) is selected from a shape model library, and the object from the image is compared with it.

Once the shape is determined and compared, the food item's overall 3D size is determined.

The researchers note that experimental tests on the device's ability to identify food shapes whose volume was known showed that the device "demonstrated satisfactory performance."

Food databases, such as the Food and Nutrient Database for Dietary Studies (FNDDS), are then used to determine the calories and nutrients in the food by sending food name and portion size data.

Calorie-counting accuracy