Robot usage in the fields of human support and healthcare is expanding. Robotic devices to assist humans in the self-feeding task have been developed to help patients with limited mobility in the upper limbs but the acceptance of these robots has been limited. In this work, we investigate how to quantitatively evaluate the comfort of an eating assistive device by estimating the interaction forces between the human and the robot when eating. Rather than using expensive or commercially unavailable devices to directly measure the forces involved in feeding, we use an accelerometer to estimate these forces, which are calculated using a previously observed estimation of the system mass and the measured acceleration during the feeding process. We experimentally verify our concept with a commercially-available eating assistive device and a human subject. The evaluation results demonstrate the feasibility of our approach.