Why eating less protein makes you hungrier
Dietary protein restriction elevates FGF21 levels and energy requirements to maintain body weight in lean men
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Replacing protein with carbs or fat had no effect on the increased calorie intake—only protein restriction mattered.
Most people assume carbs or fats are the culprits behind overeating, but here, the body responded identically regardless of what replaced protein—proving protein itself is the trigger.
Practical Takeaways
If you're trying to maintain weight, avoid dropping protein below 15–20% of daily calories—your body will naturally push you to eat more.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Replacing protein with carbs or fat had no effect on the increased calorie intake—only protein restriction mattered.
Most people assume carbs or fats are the culprits behind overeating, but here, the body responded identically regardless of what replaced protein—proving protein itself is the trigger.
Practical Takeaways
If you're trying to maintain weight, avoid dropping protein below 15–20% of daily calories—your body will naturally push you to eat more.
Publication
Journal
Nature Metabolism
Year
2025
Authors
T. S. Nicolaisen, A. E. Lyster, K. Sjøberg, Daniel T. Haas, Christian T. Voldstedlund, Annemarie Lundsgaard, J. K. Jensen, Ea M Madsen, Casper K Nielsen, Mads Bloch-Ibenfeldt, N. J. Wewer Albrechtsen, Adam J. Rose, Natalie Krahmer, Christoffer Clemmensen, Erik A. Richter, A. Fritzen, Bente Kiens
Related Content
Claims (5)
When lean, healthy men consume a diet with very low protein for five weeks while maintaining the same total calorie intake, they naturally eat more food to keep their weight stable, suggesting that low protein intake increases the body’s energy needs for weight maintenance.
When lean men reduce their dietary protein intake, their blood levels of a signaling molecule called FGF21 rise significantly within five weeks, and this rise is closely tied to the increased calorie intake needed to keep their body weight stable, indicating FGF21 may play a role in connecting protein consumption to energy use.
In lean men, reducing protein intake alters mitochondrial proteins in fat tissue, increasing some components involved in energy production while decreasing others, which may lead to higher energy use.
When male mice are fed a low-protein diet, their fat tissue undergoes changes in mitochondrial function, but these changes do not occur if the mice lack the FGF21 protein, showing that FGF21 is necessary for the metabolic response to protein restriction.
When people reduce the amount of protein in their diet to 10% of their total calories, they tend to eat more total calories without trying.