I actually made such a lifestyle choice sometime in August 2017. I identify as a pescetarian as I just couldn't give up my favorite seafood. I don't know about any internal differences that are unseen. But I did happen to drop from 250lbs at my peak to around 221lbs as of today. I'd say this alone has impressed me beyond my wildest expectations. This took a LOT of willpower as I had just moved to Vegas a month prior. Combine a completely new place with new food to try, along with Vegas already having some of the best tasting dishes, it was just an unfair recipe for disaster. I pushed through and actually stumbled upon various vegan places in Vegas and made the ultimate decision that all vegan desserts taste 1000% better than their egg/cowmilk counterparts. I don't regret the decision and I really thank the film "What the Health" for changing my viewpoint on the very first watch.