Well, your original question was, "Is MSG going to ruin my low-carb diet?" This is highly subjective, so it doesn't really matter what studies show. I'm sure there are plenty with all kinds of results (google is your friend. )

It should be self-evident that people will eat more of something if it tastes really good. I can give you a laundry list of foods that I'd have to choke down if they didn't have sweetness, salt, and/or savory-ness added to it. So it's really something you have to figure out with individual foods. I just used this example in another recent thread, but mine would be pork rinds.

For well over a decade, the only pork rinds available near me had the ingredients of pork skin, lard, salt, and nothing else. I'd never finish more than a third of a bag at a time. I just wanted them to dip in salsa and sour cream, or what not. More recently, I discovered a new brand that was seasoned with garlic powder. I finished the whole bag in one shot. I read the ingredients - MSG added. I still buy these, but I'm conscientious to not just pop open the bag when I'm hungry. I'll limit my portion and have them with guacamole or something.