When total protein intake is low, meals with added leucine lead to a greater decrease in feelings of hunger than meals with different amino acid profiles.
Mechanism
Synthesis from 3 studies
Leucine in a low-protein meal activates special cells in the gut that send signals to the brain to stop feeling hungry. These signals travel through nerves and hormones to turn down the brain's hunger signals, making you feel full even though you didn't eat much protein.
Most probable mechanism
When leucine enters the gut after a meal, it activates special cells in the intestine that release hormones that tell the brain to stop feeling hungry. These hormones travel through the blood and nerves to the part of the brain that controls hunger, turning down signals that make you want to eat.
Leucine is absorbed from the gastrointestinal tract into systemic circulation following ingestion of a leucine-enriched meal, resulting in elevated plasma concentrations above 450 µM.
Elevated leucine concentrations activate nutrient-sensing receptors on enteroendocrine L-cells in the small intestine, triggering the secretion of satiety hormones including peptide YY and glucagon-like peptide-1.
Secreted satiety hormones bind to receptors on vagal afferent nerve terminals in the gut wall, initiating neural signals that travel to the nucleus tractus solitarius and hypothalamus.
Neural and hormonal signals converge in the arcuate nucleus of the hypothalamus to inhibit neurons that promote hunger (NPY/AgRP) and activate neurons that suppress hunger (POMC/CART).
This neural reprogramming reduces subjective hunger and increases perceived fullness, independent of total caloric or protein intake.
Less supported by current evidence, but not ruled out
Leucine triggers muscle cells to start building more protein, and this process sends a signal to the brain that reduces hunger, even if the total amount of protein eaten is low.
Leucine enters skeletal muscle cells and binds to Sestrin2, releasing inhibition of the mTORC1 complex.
Activated mTORC1 increases translation initiation and muscle protein synthesis, altering cellular energy and amino acid flux.
Metabolic changes in muscle generate circulating signals that communicate with the hypothalamus to reduce appetite.
Evidence from Studies
Supporting (2)
Community contributions welcome
Consumption of High-Leucine-Containing Protein Bar Following Breakfast Impacts Aminoacidemia and Subjective Appetite in Older Persons
Consuming Lower-Protein Nutrition Bars with Added Leucine Elicits Postprandial Changes in Appetite Sensations in Healthy Women.
Contradicting (1)
Community contributions welcome
Postprandial plasma amino acid and appetite responses to a low protein breakfast supplemented with whey or pea protein in middle-to-older aged adults
Gold Standard Evidence Needed
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