Further, not all people are the same, so "healthy" actually varies from person to person. In at least one area this is dramatic: Some people are insulin sensitive and some are insulin resistant. I looked at the nutrition label on soylent. It might be healthy for insulin sensitive people, who generally tend to be naturally skinny.
But this would be a terrible thing for someone who is insulin resistant to consume. It has a very high amount of carbs and fat, which means that your body will see the carbs, blood sugar will spike the insulin will spike very high to compensate (since you're resistant you need more of it to get your blood sugar down) and the high levels of insulin tell the body to start storing fat... consequently making you fatter.
Unfortunately, so much of the diet science assumes everyone is the same, and ignores the insulin sensitivity factor (and I bet there are several other factors going on as well that aren't understood.)
But this would be a terrible thing for someone who is insulin resistant to consume. It has a very high amount of carbs and fat, which means that your body will see the carbs, blood sugar will spike the insulin will spike very high to compensate (since you're resistant you need more of it to get your blood sugar down) and the high levels of insulin tell the body to start storing fat... consequently making you fatter.
Unfortunately, so much of the diet science assumes everyone is the same, and ignores the insulin sensitivity factor (and I bet there are several other factors going on as well that aren't understood.)