Does the heart change size when someone has massive weight change?

Obesity & heart size: No. The heart size generally does not increase from obesity itself, unless there is also hypertension or cogestive heart failure. In obese people, the layer of fat in the membrane around the heart (parietal pericardium) does contain more fat, but that is outside the heart itself. But massive obesity can result in extra strain on the heart and can lead to heart failure.