The specific ways weight gain and loss alter facial appearance through fat distribution, and how this interacts with your underlying bone-based face shape.
Fat Distribution Is Not Uniform
Facial fat is distributed across several distinct compartments (buccal/cheek fat, submental/under-chin fat, and others), and these compartments don't gain or lose volume at identical rates — which is why weight change affects some areas of the face (commonly cheeks and under the chin) more visibly than others for most people.
Weight Gain and Jaw Definition
Increased submental fat is one of the more visible effects of weight gain on the face, often reducing visible jawline definition even when the underlying bone structure hasn't changed — this is a fat-layer effect, not a change to your fundamental face shape category.
Weight Loss and Cheek Volume
Significant weight loss often reduces buccal fat pad volume, which can make cheekbones appear more prominent and, in some cases, shift a face's visual reading from round toward a more oval or angular appearance even though bone width measurements remain the same.
Your Bone-Based Shape Category Persists
Because the face-shape categories on this site are built primarily around bone-based width measurements (forehead, cheekbone, jaw), your core category is more stable across weight fluctuation than your face's overall softness or definition — worth remeasuring at a stable weight if you're uncertain, but don't expect your fundamental shape to change dramatically with typical weight fluctuation.