I'm 3 months post tummy tuck. It looks good, but after I eat and sit down I have a round belly. Is that fat or swelling? (Photo)

The outcome looks good based on these photographs.  The fact that you can see a change in the contour of the abdomen after you eat is normal.

First off, thank you for the picture and congratulations on a good result.Your abdominal contour looks good and any change in contour after eating is normal and to be expected.  Without the benefit of an examination, I can't tell how much swelling you have, but this is to be expected for several months post-op, sometimes even up to 6 months or more.Stay healthy, eat right, and your abdominoplasty results will last a very long time.Best, Dr Markarian

A typical abdominoplasty is a powerful procedure that
often removes and reposition tissue of the abdominal wall for better contour
and aesthetics. After an abdominoplasty, the skin swells from the trauma of
surgery as fluid collects and the tissues become edematous. This can often lead
to small contour irregularities in the early post-operative period. These
irregularities often settle out over 3 to 6 months as the swelling resolves and the tissues
soften. Transient swelling or changes in abdominal contour are common after eating and when sitting - even after abdominoplasty. A detailed examination will help clarify the situation. Close follow-up with
the surgeon is essential.

 It looks as though you  Have gotten a good result. Dr. RAND in his previous comment is completely accurate and the restoration of abdominal wall contour from the abdominoplasty can unmask this normal physiologic phenomenon.

as far as it can be seen in your pictures you are having good results, what you describe can be caused because you are eating and now you notice that the abdomen grows after the food is in your stomach,it could also be possible that swelling makes your belly more remarkable after eating, remember that swelling can be present for up to six months and in some cases even later. Best wishes!

What you are describing is totally normal after eating, you just see it more now that your abdomen is flatter. When we eat, we also swallow air and the food we eat produces some gas in the intestines plus the volume of the food itself all produces swelling and isn't a sign of any problems.