Why You Sometimes Do Not Feel Full (and How Protein Leverage Explains It)

Confession time: I used to be a volume eater. I’d eat until I was over-stuffed, waiting for that “I’m full” signal that either didn’t show up… or I wasn’t paying attention to. That was before.

Even now, on my meat-based ketogenic/carnivore diet, I sometimes still bump into that “never full” feeling. And I know I’m not alone. I was talking about it with a friend earlier this week. She eats similarly to me.

Why does this happen?

Meet the Protein Leverage Hypothesis

Researchers Raubenheimer & Simpson (2005) proposed something brilliant called the Protein Leverage Hypothesis (PLH). I learned about it a few years ago. Here’s the short version:

• Humans (and other animals) will eat until they reach their protein target.
• If a diet is low in protein but high in fat or carbs → appetite keeps pushing until that protein threshold is met (often leading to overeating).
• If a diet is high in protein → satiety kicks in sooner, often leading to lower total calories.
• Think of protein as your body’s thermostat. Hunger won’t shut off until you’ve “hit temperature.” I hope that makes sense.

That’s the big picture.

Why Not All Proteins Feel the Same

Here’s where it gets interesting: not all protein foods flip the satiety switch equally.

For example, have you ever noticed how:

• A plate of chicken breast or grilled fish leaves you full for hours?
• But a ribeye sometimes feels heavy… yet doesn’t deliver that same “done eating” signal right away?

You’re not imagining it. That difference isn’t about calories — it’s about how protein and fat interact with your satiety hormones and insulin but that’s another story.

The Details Behind the Difference

Protein-to-Calorie Density

• Chicken & white fish: ~90–95% of calories from protein.
• Lean beef/bison: closer to 65–75% (thanks to intramuscular fat).
• Chicken/fish deliver a bigger “protein punch” per bite.

Digestive Kinetics

• Beef/bison: more connective tissue and longer-chain fats = slower digestion.
• Slow digestion can feel “heavy,” but heavy ≠ satiated. And yet some of us (ME) we do better with the leaner beef/bison options. We are all different.

Amino Acids & Hormones

• Chicken/fish: higher in certain satiety-linked amino acids (like leucine, lysine, tryptophan). These trigger GLP-1, PYY, and CCK more sharply.
• Beef: still great and nutrient dense, but signaling is a little slower in some people because fat blunts the amino acid surge.

Personal Physiology

• Some people just feel better with poultry/fish (like my friend I mentioned earlier)
• Others (like me) don’t feel satisfied without red meat. Both are valid.

The Bottom Line

• Chicken & Fish → Quick, sharp satiety signals.
• Beef & Bison → Slower, heavier, more gradual satiety signals.

The hormones are the same (GLP-1, PYY, CCK) — what changes is how fast and how strong they’re triggered.

Think of it like two alarms:

• Chicken/fish = loud, quick siren.
• Beef/bison = slower, delayed bell.
  Both work… but the timing is different.

What This Means for You

If you’re:
✔️ Trying to manage appetite
✔️ Eating for fat loss
✔️ Or just wondering why some meals satisfy you more than others…

Here’s the takeaway:

• If lean proteins (chicken/fish) “work” better for your satiety switch, lean into them.
• If red meat makes you feel nourished, that’s valid too.
• Best of all? Mix your protein sources (poultry, beef, eggs, fish). You’ll cover nutrient bases and keep your satiety hormones happy. And always eat your protein first. We want to have optimal protein so let that be your focus.

The Protein Leverage Hypothesis explains why protein itself is the driver. The chicken vs. beef thing? That’s just one real-life example of how it plays out in your body.