Satiety

The science here is protein tends to promote fullness through several physiological mechanisms.

Fiber can contribute to Satiety, although its effects depend on the food and the type of the fiber that you're getting.

Food volume and water content influence how physically filling a meal feels.

Eating speed and food texture can also affect how we experience fullness, and two meals with similar calories can produce different levels of satisfaction.

So that's the benefit.

That's it

... uh, protein produces far more satiety than fat and carbs.

In Sarum Close by Lord Alfred Douglas, recording by Hernandez.

Tired of passion and the love that brings Satiety's unrest and failing sands Of life, I thought to cool my burning hands In this calm twilight of grey Gothic things.

But Love has laughed, and spreading swifter wings Than my poor pinions, once again with bands Of silken strength my fainting heart commands, And once again he plays on passionate strings.

But thou, my love, my flower, my jewel, set In a fair setting, help me or I die To bear Love's burden, for that load to share Is sweet and pleasant; but if lonely I Must love unloved, 'tis pain.

Of all the things we could focus on, vitamins, minerals, cutting carbs, avoiding fats, why is there this intense, singular focus on protein above all else?

It all comes down to the neurobiology of satiety

Feeling full

Exactly

Satiety is your body's deeply complex internal signaling system.

It is a cascade of hormones like leptin and peptide YY that travel from your gut to your brain, essentially shouting, "Okay, we have acquired enough essential nutrients.

You are full.