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The Protein Leverage Hypothesis: Is This Why So Many People Are Overeating?

October 28, 2024

Have you heard of the “protein leverage hypothesis”?

This fascinating concept—proposed by two researchers at the University of Sydney—might be a big reason so many people eat far more today than they did a few decades ago.¹

It’s the idea that, above all else, you’re biologically programmed to seek a specific percentage of protein in your diet, compared to carbs and fat.

And, if you fall short of the right ratio, your body is hard-wired to keep eating.

Here’s the kicker: The researchers believe even small reductions in protein percentage can lead to a sharp increase in calorie intake—regardless of how much protein you actually eat.

Could this actually be true? Are you at risk? And what’s the right protein percentage to avoid this overeating trigger?

Keep reading for all the details—including how a tiny drop in protein percentage caused people to eat 500 more calories a day.

Quick Background

Generally speaking, humans naturally tend to eat about 10 to 25 percent of our daily calories from protein, “with 15 to 20 percent most common,” according to the University of Sydney scientists.²

Obviously, that percentage can be greater if you choose to follow a high-protein diet. But 15 to 20 percent is the usual range for those not aiming for a specific amount.

The researchers say there’s a good reason for this: It’s known as “nutrient-specific appetite.”

Why Your Body Craves Protein

Nutrient-specific appetite is just what it sounds like: You have a built-in appetite for certain nutrients. This is true for protein, carbohydrates, fats, and some micronutrients, such as calcium and sodium.²

But, say the researchers, your body prioritizes protein over everything else. That’s because it’s critical for survival. As a bonus, this strategy tends to work out pretty well for the other nutrients you need, too.

The reason: When you eat a satisfying whole-foods diet that provides 15 to 20 percent of your calories from protein, you’re unlikely to be severely deficient in other essential nutrients. As the researchers put it, they “come along for the ride.”²

Problem is, most people these days aren’t eating a satisfying whole-foods diet. And that’s where the trouble starts.

Do You Suffer from “Protein Dilution”?

Compared to a whole-foods diet, a diet high in ultra-processed foods—the hallmark of the standard American diet—is overloaded with carbohydrates and fats. This, in effect, lowers the percentage of protein per bite.

Scientists call this “protein dilution,” and it’s rampant in today’s society—thanks to fast food meals, packaged snacks, and sugar-laden beverages.

When your body senses protein dilution, it responds by increasing your appetite in an attempt to make up the difference.

The result? You end up consuming excess calories because your body is trying to compensate for what it perceives as a lack of protein in your diet.

When Protein Goes Down, Calories Go Up

Let’s look at a real-life example of how protein dilution can affect your calorie intake.

In a tightly controlled study, NIH researchers took 20 volunteers and had them follow two different diets: an ultra-processed foods diet and a whole-foods diet. After 14 days, they switched the participants to the opposite diet.³

Both diets provided the same total calories, protein, carbs, fat, sugar, sodium, and fiber. But participants were allowed to eat as much or as little as they wanted.

The findings? When eating the whole-foods diet, the participants naturally consumed about 500 fewer calories per day than they did on the ultra-processed foods diet. Those extra calories—on the processed foods—came entirely from carbs (280 calories) and fat (230 calories).

And get this: Even though both diets provided the same total amount of protein, the ultra-processed group ate just 14% of their calories from protein, while the whole-foods group hit 15.6%.

In other words, the ultra-processed diet diluted their protein intake with carbs and fats—and that could be a key reason they ate more.

What Can You Take Away from All This?

Although the protein leverage hypothesis has been around for almost 20 years, it’s still called a hypothesis for a reason: It’s hard to prove conclusively.

However, the basic idea—that your body prioritizes protein over other nutrients, and when you don’t get enough, you tend to eat more—makes sense.

Here’s what you need to know to make the most of this concept in your daily life.

Takeaway #1: There’s probably an upper limit to protein leverage.

When you learn about the protein leverage, it might be easy to assume that the higher your percentage of protein, the better.

But the research is pretty “iffy” here. The studies that directly investigate the protein leverage hypothesis often compare different protein percentages but don’t always match total protein intake. These studies are usually small, very short-term, and have mixed results.

For instance, one study investigated protein intakes of 10, 15, and 25 percent and found that when people ate a diet that was 10 percent protein, they ate more total calories compared to when they consumed a diet that was 15 or 25 percent protein. Yet there wasn’t a difference in calorie intake between the 15 and 25 percent groups.⁴

Still, citing the entire body of evidence, the University of Sydney researchers propose that “protein leverage occurs across the range from 10 percent to 30 percent.” Meaning that there could be some benefit—in terms of protein leverage—to going as high as 30 percent of your calories.¹ (Note: The researchers believe that below a certain level—specifically 5 percent—protein intake is so dangerously low that it disrupts your body’s usual response.)

Takeaway #2: There’s no magic number.

Based on the current data, a good minimum target for protein is between 15 and 20 percent of total calories. The exact number is probably going to depend on your individual physiology. So, if you want to hedge your bets, aim to make protein account for at least 20 percent of daily calories.

Of course, you can certainly shoot higher, which offers lots of benefits, such as displacing extra calories from carbs and fat, supporting fat loss, and optimizing your ability to maintain and build muscle.

In fact, I often recommend consuming one gram of protein per pound of body weight—which for many people, might be around 25 to 35 percent of calories.

But, if you find that challenging (a lot of folks do), first targeting 20 percent of your daily calories is a great way to make progress and help keep your appetite in check. (If you’re looking for a simple way to increase your daily protein intake, check out these convenient protein powders in our store.)

Takeaway #3: Not all protein dilution is “bad.”

There seems to be an exception to the “you eat more when the proportion of protein in your diet is diluted.” And it’s this: fiber and water.²

When you eat foods high in fiber or water, they add volume to your diet without adding calories, helping you feel full.

This is why people who follow a plant-based diet—often higher in fiber—can eat a lower percentage of protein and still feel satisfied. The fiber helps regulate appetite, preventing the overeating that might happen if protein were diluted by calorie-dense fats or carbs.

The best of both worlds? Eat lots of protein and fiber.

Takeaway #4: This doesn’t solve the ultra-processed foods problem.

To take full advantage of protein leverage, the quality of your food choices really matters.

If you continue to rely on a diet heavy in ultra-processed foods, you’re likely to struggle. That’s because ultra-processed foods are designed to be hyper-palatable—so tasty that they can be hard to stop eating.

The reality: Whether you’re eating more because your body is craving protein or because the food is engineered to be irresistible, the result is the same—you end up consuming more calories.

Takeaway #5: Obesity is “multifactorial.”

Protein dilution doesn’t explain all the reasons people struggle with weight management. So, even though it offers valuable insights, it’s not a panacea.

After all, people overeat for many reasons—whether it’s because they’re stressed, lonely, depressed, aren’t able to easily access healthy foods, don’t know how to prepare nutritious meals, or a thousand other reasons that vary from person to person. Plus, let’s not forget the influence of food marketing, which promotes unhealthy, processed foods and normalizes large portions.

But remember: With every positive step you take to improve your nutrition and health—whether it’s increasing your protein intake or reducing processed foods— you’re stacking more daily actions in your favor and making progress to a healthier you.