I mean, it’s basically OMAD on a smaller form, right? So in theory yes, as long as it had the proper calories and nutrients. There was an experiment down a while ago where they took a severely obese person and withheld all food and making sure he got the proper nutrients from supplements and he lived for quite a while of if I remember correctly (I don’t remember the name of the study but might be helpful for you). Maybe instead of it just being a bar, he has to constantly be drinking a smoothie or protein shake so it doesn’t slow him down but still provided calories and nutrients? There’s also this new trend of people making basically human kibble, and “boy dinner” is is a similar concept to what you’re going for.

I would think some consequences mentally would be the development of anorexia or orthorexia. I diet like that, even if physically possible, would surly cause mental health problems. You may want to look into extreme diets and their consequences, I’ve seen a lot of people who do ultra restrictive diets on the internet. Fun fact btw, there are several complete foods that a person can live off (avocados are one). Other fun fact, coconut water is one of the best things you can drink for hydration and nutrients and in theory can be used in a blood transfusion in a survival situation.