Probably best for Soylent drinkers to regularly chew gum. It'd be pretty awkward to discover after a few months that your jaw muscles have atrophied so severely that you have trouble chewing even the softest dry foods.
Perhaps its counter acted by them telling me all the time how much better it is than solid food :-).
But more seriously you do have a valid (if taken to an extreme) point. But similar arguments are made by people on segways losing walking endurance (or cars even). Actual atrophy seems to require complete non-use.
People using motor vehicles all the time absolutely causes atrophy. Lack of mobility among the sedentary (especially sedentary and obese) part of the population is a serious problem. There are a substantial number of people who have difficulty walking even a couple of blocks, not through any prior injury or disability, but just through disuse of their legs.
My wife and I were at the Biltmore estate in North Carolina a couple years ago. We wandered through the gardens, and we were chatting with a couple of ladies about what we had seen. They were shocked that we had walked a half mile from the parking lot instead of taking the shuttle. “You walked all the way from the house to here?!”
But more seriously you do have a valid (if taken to an extreme) point. But similar arguments are made by people on segways losing walking endurance (or cars even). Actual atrophy seems to require complete non-use.