Serving Size

40oz large? :O

That's pushing 1.25 litres!

Our large sodas (In NZ) are usually around the 600-700ml mark.

High-fructose corn syrup (hfcs) is the main culprit for weight gain. That's why it's somewhat laughable to see a fat person order a diet soda, thinking they're doing herself a personal favor.
Soda was originally made with real sugar. In fact, very few countries switched to hfcs, the U.S being one of them. Mainly because it is far cheaper to make soda with it. (Not to mention cookies, frostings, or anything sweet; check the labels, people!)

"They wash your food through your stomach making you hungrier sooner! "

that's the funniest & stooopidest thing i've ever heard

this is one reason obeseity is such a plague here

@Eli - If diet soda makes you fatter by "wash[ing] your food through your stomach making you hungrier sooner", wouldn't water do the same?

Congrats on the weight loss!