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Technology to Measure Energy Balance

shoe sensorToday’s technology is being used in many areas of health management. At the national Obesity 2011 meeting, Dr. Edward Sazonov presented a talk on the goal of moving towards the ability to accurately measure energy balance with sensors. (energy balance defined as calories consumed minus calories burned).

Dr. Sazonov began his talk with an overview of why energy balance is so hard to measure. In order to directly measure calories burned, you’d have to measure all heat produced by an individual. The only way to truly accurately do this is to have the individual remain in a closed room. Additionally, you’d then measure caloric content of all foods served to get an accurate measure of the calories they’re taking in. But, of course, this is not possible in a natural living environment, and without this highly controlled setup, it’s almost impossible to completely accurately measure energy balance.

Currently, the standard method of measuring food intake relies on self-reported dietary recall methods, which are notoriously unreliable. Other than not getting an accurate report of how many calories an individual is taking in, there is a high burden on the individual who generally uses a food diary to record everything they eat. The question Dr. Sazonov has been focusing on is: can we use advances in technology to design devices that are often with the individual, and capture their EE/EI and provide use that to provide feedback?

Years ago, we didn’t have the high availability of personal technology that we do today, and some of the recent technology advances are making the accurate measurement of energy balance more likely to succeed: Tremendous progress has been made in the technology of sensors; high computing power is much more accessible; and cell phones and wifi are readily available for data delivery and communication.

With the technological advances of the last few years, we’re now at a better place to develop sensors that are unobtrusive, use pattern recognition to identify events of interest, and provide real-time feedback to the individual. Dr. Sazonov discussed his new shoe-based sensors called SmartShoe. The shoe has an accelerometer, pressure sensor, and wireless electronics. It is able to communicates with a cell phone, recognizes and logs the position of the individual, and can provide feedback in order to motivate behavior change, such as the SmartShoe could send a text to a person’s smartphone saying “You have been sitting too long, take a walk”. In initial tests, SmartShoe was capable of 98% average recognition accuracy in classifying 6 major postures and activities.

Although SmartShoe is an exciting advance in the measurement of expended energy, the other side of the question is – can wearable sensors measure energy intake? Dr. Sazonov says that right now most common form of EI tracking is a diary, which requires conscious, ongoing effort on the individual’s part to report what they eat. His approach combines an acoustical swallowing sensor, a jaw motion sensor, and a hand-to-mouth gesture sensor.

This combination enables what’s called Monitoring of Ingestive Behavior (MIB). The technology measures swallowing frequency and number of chews per swallow. These metrics can be used to estimate mass of ingestion (in test results presented by Sazonov, they showed a 90% accuracy for solids, and an 80% accuracy for liquids in a chewing/swallowing test that compared several ingested substances including water, yogurt, pizza, and no food.)

In addition, Sazonov discussed a prototype of AIM (Automatic Ingestion Monitor) which has a bluetooth neck medallion that captures jaw motion, hand to mouth gestures, and has a 3D accelerometer. The data collected is sent to a cell phone, which can, in turn, provide the user with feedback on their eating behaviors, or prompt them to enter their food into a diary, or take a picture of their meal.

Sazonov shared that their ongoing work includes improving sensors, and improving the accuracy and sophistication of their models. He says these innovations could lower the burden and inaccuracy of individuals having to carefully record their own EE and EI, and this “gives us hope that one day energy balance can be objectively and accurately captured with wearable sensors.”

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