I wonder if this applies to Huel (https://huel.com), essentially the British version of Soylent.
I've been using Huel on-and-off for a few months — to replace my lunches for a few days each week, or when I don't fancy breakfast, or if I realise I haven't eaten enough calories in a day. I might start regularly replacing my breakfast with it, now.
The best effect is re-examining my relationship with food. If I over eat or eat rubbish I really notice it now and just that awareness has naturally improved the rest of my diet.