Ray's Take

I was thinking about protein, and came across something called the protein leverage hypothesis (PLH).

What is it?
The PLH proposes that our bodies will always target a certain % of calories coming from protein. This means we will want to eat until we hit ~15% of the total calories we eat being protein.

The originators of the PLH believe that the world has gotten fatter (70% of USA being overweight or obese) because the total calories we eat is more weighted toward fat and carbs now.

So if there are more carbs and fat to eat, this reduces the amount of protein we eat (as a % of total cals), and our bodies stay hungry. They refer to this as protein leverage:
Studies have shown that humans, like many other species, regulate protein intake more strongly than other dietary components, and consequently if dietary protein is diluted there is a compensatory increase in food intake—a process called protein leverage.

Simply stated, if the % of calories you eat are too low in protein, you'll automatically eat more.

Data

This is data shown a review paper (cited below):

The X-axis is the percent of protein people ate, and the Y axis is the total calories they ate. As you can see, there is a trend toward the higher the % of protein, the less people ate. Keep in mind this is combining data from 44 studies that measured dietary protein %, not one study. This isn't always "good".

They also look at randomized controlled trials:

Again X-axis is % protein and Y-axis is total cals. This basically shows that if total protein increases from 10% of cals to 30%, people ate less cals. However PLH does not apply at very low levels (5% protein) where malnutrition may be at play.

I know eating protein is important for muscle growth/preservation, it tastes good, I eat a lot of it, so sure I'll buy into the PLH. However, the authors published the review of PLH in 2023 in an obscure journal, so I was kind of skeptical.

However, I found out that Kevin Hall wrote a review on the PLH in 2020 so I got more interested.

I like Kevin Hall. He's the lead researcher for the NIH on obesity, and calls it like it is, based on data. I think he's reasonable and smart (even though other nutrition researchers hate him for questioning their models).

What did Kevin do?
He made some fancy math equations that would model how much extra calories people would eat, and how much weight they would gain, given lower protein % based on perfect protein leverage and partial protein leverage.

Here is the most important data:
They first used Food and Agriculture Organization of the United Nations (FAO) to check how much % protein people ate since 1973. (not shown here). Suffice to say people started eating less % protein since then.

They then looked at observed weight changes by year:

- The top line is how much people actually weighed by year. This weight data was from the National Health and Nutrition Examination Survey.
- The solid line is how much weight the PLH would have predicted with full leverage (100% of the predicted increase in calories based on lowered % protein).
- The dotted line is how much weight the PLH would have predicted with partial leverage (50% of the predicted increase in calories based on lowered % protein).

The data basically shows that too having % of protein be low could actually cause people to eat more and gain weight.

Kevin's conclusion:

Therefore, contrary to my previous conclusion (he previously did a separate analysis saying PLH was wrong), even partial protein leverage could potentially play an important role in obesity that should not be ignored.

My conclusion:

Make sure you get enough protein - no brainer.

Now there is decent chance that eating more protein can make you more full so you eat less other shit. Amazing

How much? Read this next.

Citations

Hall KD. The Potential Role of Protein Leverage in the US Obesity Epidemic. Obesity (Silver Spring). 2019 Aug;27(8):1222-1224. doi: 10.1002/oby.22520. Epub 2019 May 16. PMID: 31095898; PMCID: PMC7147114.

Raubenheimer D, Simpson SJ. Protein appetite as an integrator in the obesity system: the protein leverage hypothesis. Philos Trans R Soc Lond B Biol Sci. 2023 Oct 23;378(1888):20220212. doi: 10.1098/rstb.2022.0212. Epub 2023 Sep 4. PMID: 37661737; PMCID: PMC10475875.