It is incredible how digestion works when you ingest only meat and zero fibre, as experienced by someone with IBS: digestion is simply a non-event. Bowel movement are rare (once every 3 days after adaptation) with no fuss and no constipation. Sit and go. Farts stop being a thing. There is very little undigestable residue in meat.
And in general the whole low carb biology feels completely different: I literally feel my heart and circulatory system working with much less effort; it's difficult to explain. A decent comparison is that it's as if fatty acids and ketones are a much cleaner fuel than glucose, which is excellent at short-lived bursts of energy (and the body can create by itself through gluconeogenesis) but not for daily, low-effort maintenance of the body. Let alone the mental calm and lowered anxiety of it: I take ADHD meds and they are more effective on low carb, and in general my mood is more stable (beta-hydroxybutyrate seems to activate the GABAergic system, reducing neuronal excitability, IIRC)
I empathise with the plight of animal suffering, but my theory is that diet and sustainability are clashing against a truly uncomfortable reality: homo sapiens has evolved for million of years to live on animal flesh
(much more than we had agriculture), with seasonal, sour fruits and honey to fatten up for the winter (with fructose being a known obesogenic sugar). I get why people want to feel in control over their impact on the world, and it's admirable, but my body is very clear on what works and what doesn't.