  Dietary assessment is a key contributor to monitoring health status. Existing
self-report methods are tedious and time-consuming with substantial biases and
errors. Image-based food portion estimation aims to estimate food energy values
directly from food images, showing great potential for automated dietary
assessment solutions. Existing image-based methods either use a single-view
image or incorporate multi-view images and depth information to estimate the
food energy, which either has limited performance or creates user burdens. In
this paper, we propose an end-to-end deep learning framework for food energy
estimation from a monocular image through 3D shape reconstruction. We leverage
a generative model to reconstruct the voxel representation of the food object
from the input image to recover the missing 3D information. Our method is
evaluated on a publicly available food image dataset Nutrition5k, resulting a
Mean Absolute Error (MAE) of 40.05 kCal and Mean Absolute Percentage Error
(MAPE) of 11.47% for food energy estimation. Our method uses RGB image as the
only input at the inference stage and achieves competitive results compared to
the existing method requiring both RGB and depth information.
