When you gain weight, does your heart grow in size? If you work out, does the heart muscle shrink or get bigger?
No, the heart does not grow in size upon weight gain and if one works out regularly and intensely, one may get athletes' cardiomegaly.
In weight gain, the heart is not expanding but rather exerts more effort to pump blood. In working out, the heart muscles are used more regularly thus it may grow larger depending on how frequent and intense your work out is. Many marathon and triathletes have been diagnosed with cardiomegaly.. (heart enlargement).