Athletic and mental performance. Paleo alongside intermittent fasting is super popular amongst endurance athletes reporting significant energy increase comparing to popular liquid vegan diet; a low-carb, high fiber, medium fat/protein diet also has significant positive effects on some mental disorders (like the currently "popular" BPD or ADHD). And you often see vegans with significant health problems later in life as well (cancer), though this might be side effects of past extremes such as eating junk fats like margarine and plenty of sugar because of mistaken belief those were healthier alternatives, making them as ill as frequent red meat consumers. Will see how this would fare for Soylent users in a few decades.

We probably shouldn't be on either side of extreme - vegan vs meat-only but rather figure out what works for our DNA/RNA-based protein factory best (maybe using personalized ML?) and exercise self-restraint.