So you prefer a diet engineered by humans (who, with our rather limited understanding of nutrition, can't even decide on whether carbs are a good thing) to a diet engineered and field tested by evolution over millions of years? Not the bet I would make, but to each their own, I guess.

Several other points:

1. The OP was remarking that they had a hard time maintaining weight. Anybody who has done GOMAD (gallon of milk a day) can tell you that large quantities of milk will head off the possibility of weight loss.

2. Is there any reason to believe that the agricultural inputs to something like Soylent aren't just as heavily subsidized as you claim milk to be?