Urgh. So basically we're giving advice to a friend on tips to feel healthier. I've had a talk to this guy about switching to water and drinking a gallon a day before instead of the 12 pack or more of regular pop he drinks a day. So it's excessive. He had a bunch of reasons like he had nightmares when he just drank water.
So he made a Facebook post and I advised that he should try switching to diet pop because I recalled the conversation we had when we worked out. His ex girlfriend is all like "it's not healthier! It's never better to drink diet pop!" I asked her to provide peer reviewed research but I doubt she is going to. Chances are it'll be some health site that just says that it's not healthier. There was a study that said they didn't notice any health benefits when reviewing other studies.
Basically, this guy drinks too much pop. It wouldn't surprise me if he was a diabetic already. It runs in the family and he is overweight without working out a lot. Pop in general isn't good for you, but using diet pop to cut down is a lot better than consuming 1,200+ calories a day in just pop alone.
Ideally he would cut out pop. However, I believe in the real world and when he says he's not going to, it's better to offer alternatives. He refuses to drink water so advising him to drink those energy squirts (I don't know, you squirt some into the water) with caffeine won't work. Tea may work but he really loves this brand of pop. So offer the best alternative to consuming 12 cans a day and the ton of sugar it is.
Maybe she doesn't know how much pop he actually drinks. Also, running around and saying that "it's never healthier" is stupid. He probably does have diabetes but he won't go get checked out. I recommended a doctor that I liked and he still wouldn't.
It just drives me nuts when people want to make absolute statements like something is never better without looking at the bigger picture. Ideally the guy would go to the doctor and get checked out. However, he won't at the moment. It's small steps. While diet pop and regular pop isn't ideal, when the guy refuses to take something then your options are limited.