There is straight up msg, then there is 'natural flavors' or 'spices' which takes advantage of naturally occuring glutamate which is the same thing. Some foods are high in glutamate like sunflower seeds, peanuts (most nuts), cheeses, and nutritional yeast. Chic-fil-a cooks their chicken in peanut oil. Even if they add nothing else to their chicken (I fucking doubt it), that by itself would have an appetite and short-term enjoyment stimulating effect. Go look are storebought chicken, chances are it has "5% solution and natural flavors" added to it. It's all a work around to get glutamic acid in the food and you overeat.
Many times I've found myself overeating a single food, snacking on it even, despite normall eating only once a day and having eaten 900 calories or less a day with no problem. In all cases (like that unsweetened fizzy water, Earth balance vegan "butter" and certain seeds), when I dropped that food or food product, my urge to snack ceased, I flt motivated not only to get back on track with my calorie goal but even go below it just because of how not-hungry I suddenly was again, and slept better after 2-3 days of last ingestion.
I shit you not, when it came to the "butter," I was eating half a loaf of bread a day or more; just so I could have buttered toast. I don't even like buttered toast but I was inhaling it like crazy.
Bottom line, it's in every food product and in a not-insignificant amount of natural things and it does what it is meant to: get you eating more of that of whatever product is dosed with it and eat more food in general (which will likely end up being that product).