Language can play tricks with you. Doctor speak can play tricks with you.
There is no such thing as a side effect. If you ingest medication it affects the body. Some of these effects are desirable and some are unintended, but to name them side effects is just too convenient.
These unintended so called side-effects are just as important and real as the intended effects.
End of story.
So when the cardiologist asks
“Have you lost weight?”
“Yep, I don’t want my heart doing anymore work than it has to, so I eat a plant-based whole food diet, the weight loss is just a side-effect.”