6 Ways Your Body Can Change After Starting a High-Protein Diet

Walk into any grocery store and you’ll likely find a flood of protein-enriched products, from waffles and cereals to chips and desserts. While most people get enough of this essential macronutrient through their regular diets, many are now purposefully loading up to lose weight, boost energy, or build muscle.

If you’re thinking about upping your protein intake, here’s what could happen to your body.

The moment you start eating, your body releases hormones—namely ghrelin and GLP-1—that regulate appetite and glucose metabolism. Research shows that high-protein diets increase the production of these hormones, which in turn appear to reduce hunger and promote longer-lasting satiety.

Dana Ellis Hunnes, RD, PhD, MPH, a senior clinical dietitian at the University of California, Los Angeles Medical Center, suspects there may be a few reasons for this.

“It could be that you’re chewing longer on protein, it sits heavier in your stomach, or also, because of its fat content, it stays in the stomach longer (delaying gastric emptying) and may therefore keep you fuller longer,” she said.

That said, how full you feel after consuming protein may vary from person to person. “It might depend on what else you’re eating, the type of protein you’re eating, how much fat it contains, and how it was prepared,” Hunnes told Health.

Compared to carbohydrates and fats, protein requires more energy to digest, absorb, and metabolize, said Allison Childress, PhD, RDN, LD, CSSD, a sports dietitian and associate professor in the department of Nutritional Sciences at Texas Tech University.

Several studies show that many people experience a metabolism boost when starting a high-protein diet. Over time, however, this effect wanes, and only meals super high in protein continue to rev up metabolism. There is a caveat, according to Childress: Losing weight or lean mass will offset that metabolic boost.

Protein provides amino acids that directly stimulate muscle protein synthesis, the process that fuels muscle repair and growth.

After you work out—and for roughly 24 to 48 hours—your muscles become more sensitive to amino acids, explained Childress. During this period, labeled “the anabolic window,” protein intake can facilitate muscle repair, support growth, and help prevent your body from breaking down muscles for energy.

What might that feel like? According to Childress, you may experience “less soreness, improved performance in future bouts of exercise, preservation of or gain in muscle mass, and improved recovery.” You might also feel less drained, sleep better, and have fewer aches and pains, she told Health.

In the longer term, loading up on protein may change your body composition—but only if you’re also engaging in vigorous resistance training, like weightlifting, according to Christopher Gardner, PhD, the director of nutrition studies at the Stanford Prevention Research Center. “It has been proven that you can’t simply eat protein and gain muscle,” he told Health.

If you’re working out consistently, it may still take months to see noticeable muscle growth. “It requires breaking down current muscle and rebuilding it, again and again and again,” Gardner explained.

While most people won’t experience gastrointestinal symptoms, some may find they become constipated when consuming more protein, research shows.

Hunnes said this largely depends on your individual microbiome, which is the community of microorganisms living in your gut.

Protein, especially when sourced from animals, can change the microbiome and influence overall health. “What that ends up doing in the gut, symptom-wise, may depend on the individual,” she said.

When you consume more protein than your body needs—the upper daily limit for active people is .9 grams per pound of body weight, and even lower for those who are sedentary—there’s no place to store the excess. Instead, your body breaks it down. The byproducts of this process—such as ammonia—must be filtered out and excreted by the kidneys. “For most people, the human body is very efficient at this process,” Gardner said.

But for people with impaired or compromised kidney function, the kidneys can become overworked, leading to worsening kidney health, research shows. As such, this group is often advised to limit their protein intake.