Sorry mate, there is no current way to eat without eventually needing to poop and remain healthy.

Best case scenario, you can figure out an IV nutrition regimen and end up not pooping poop, while your intestines are damaged through non use. You'll likely suffer immensely if you ever decide to eat again.

Even then, things will still come out of you. Patients with extreme starvation, regardless of cause, still produce some intestinal mucosa. That stuff can and will eventually come out in small amounts.

See, the gut atrophies when it isn't being used. It takes a while to reach that point, but it's inevitable, no matter how well you keep up with IV feeding

In terms of smoothies, there's ways to feed people through a tube when they can no longer eat. The products that are used for that minimize waste, but there's still poop of some kind. So any smoothie you make yourself is also going to contain enough content that's indigestible that you'll poop eventually unless you take care to balance the soluble and insoluble fiber in the smoothie, you'll end up with smoothie poop. In other words, it comes out in a very similar state of fluidity as it went in. It takes some effort to build a smoothie recipe that doesn't have skewed proportions of fiber.

And if you want to have a healthy body, you can't just let the intestines atrophy at all. The inflammation and other secondary issues that come with gut atrophy can't be called healthy by any stretching of the term. So even IV feeding isn't healthy, no matter how well done it is.

I'm trying to remember exactly how far into IV feeding you run into atrophy issues though. There was a fairly famous case of a man that was on an IV feeding plan to lose weight, but with the recent discovery of wegovy and related drugs for weight loss, there's too damn many hits to sort through to find any of that info. But his case did include intake of low/no calorie intake orally to prevent that atrophy, I just can't remember the details of what did happen to his gut health. I know he had at least a few months where he had trouble after resuming eating, but I'm damned if I can remember any details.

I'm fairly certain you could minimize pooping with oral nutrition that lacks any products that would form waste in the digestive tract though. It wouldn't be a smoothie, since that's pureed food; and it wouldn't be healthy long term for all of the above reasons regarding the gut. But you might be able to work with specialists and figure out how to keep things from becoming so detrimental as to be inherently harmful. You'd definitely need a team though, I don't think any single specialty in medicine would cover all of the knowledge necessary to make it work long term.