Sounds similar to this paper [0] that compared the types of dietary fats eaten with cognitive decline in adults 65+.
"higher intakes of saturated fat (p for trend = 0.04) and trans-unsaturated fat (p for trend = 0.07) were linearly associated with greater decline in cognitive score over 6 years. These associations became stronger in analyses that eliminated persons whose fat intake changed in recent years or whose baseline cognitive scores were in the lowest 15%."
I, for one, am hoping it's largely to do with cheap, high-calorie ingredients and not to do with actually processing as I'm a big fan of Soylent (largely monounsaturated fats FYI) for its convenience and it doesn't get much more "processed" than that.