Estimation of Food Intake Quantity Using Inertial Signals from Smartwatches

TL;DR

This study demonstrates that commercial smartwatch inertial sensors can accurately estimate bite weight, enabling non-invasive dietary monitoring with a mean absolute error of 3.99 grams, potentially improving eating behavior management tools.

Contribution

Introduces a novel method combining behavioral and inertial features with SVR to estimate bite weight from smartwatches, outperforming existing approaches.

Findings

Achieved a mean absolute error of 3.99 grams per bite.

Demonstrated a 17.41% improvement over baseline models.

Established feasibility of using commercial smartwatches for dietary monitoring.

Abstract

Accurate monitoring of eating behavior is crucial for managing obesity and eating disorders such as bulimia nervosa. At the same time, existing methods rely on multiple and/or specialized sensors, greatly harming adherence and ultimately, the quality and continuity of data. This paper introduces a novel approach for estimating the weight of a bite, from a commercial smartwatch. Our publicly-available dataset contains smartwatch inertial data from ten participants, with manually annotated start and end times of each bite along with their corresponding weights from a smart scale, under semi-controlled conditions. The proposed method combines extracted behavioral features such as the time required to load the utensil with food, with statistical features of inertial signals, that serve as input to a Support Vector Regression model to estimate bite weights. Under a leave-one-subject-out cross-validation scheme, our approach achieves a mean absolute error (MAE) of 3.99 grams per bite. To contextualize this performance, we introduce the improvement metric, that measures the relative MAE difference compared to a baseline model. Our method demonstrates a 17.41% improvement, while the adapted state-of-the art method shows a -28.89% performance against that same baseline. The results presented in this work establish the feasibility of extracting meaningful bite weight estimates from commercial smartwatch inertial sensors alone, laying the groundwork for future accessible, non-invasive dietary monitoring systems.