A method of detecting health-related behaviors, comprising training a model with video of the mouths of one or more users, capturing video using a camera focused on a user's mouth; processing the video using the model; and outputting one or more health-related behaviors detected in the captured video by the model. A method of training the model includes preprocessing a video captured by a camera focused on a user's mouth by extracting raw video frames and optical flow features; classifying the video frame-by-frame; aggregating video frames in sections based on their classifications; and training the model using the classified and aggregated video frames. A wearable device for capturing video of a user's mouth is also described.