Among overweight or obese adults losing weight on a calorie-restricted diet, consuming 30% of calories from protein preserves muscle mass, while consuming 20% protein with a low-glycemic-index diet...
Mechanism
Synthesis from 1 study
Eating more protein while cutting calories keeps muscles from shrinking because the amino acids in protein turn on signals that tell muscles to build more protein and stop breaking down. This happens even when the body is in a calorie deficit, so muscle stays intact while fat is lost.
Most probable mechanism
When someone eats less food but more protein, the extra protein breaks down into amino acids that signal muscles to build more protein and stop breaking down. This keeps muscle from shrinking even when the body is in a calorie deficit.
Dietary protein increases plasma concentrations of branched-chain amino acids, especially leucine
Leucine activates the mTORC1 signaling pathway in skeletal muscle
mTORC1 activation increases ribosomal biogenesis and translation initiation, elevating muscle protein synthesis
High protein intake suppresses the ubiquitin-proteasome system, reducing muscle protein breakdown
Net protein balance becomes positive, preserving fat-free mass and muscle mass during energy restriction
Less supported by current evidence, but not ruled out
Eating more protein triggers gut hormones that signal fullness to the brain, causing a person to eat less food without trying, which increases fat loss while protecting muscle.
Dietary protein stimulates release of glucagon-like peptide-1 and peptide YY from intestinal L-cells
Glucagon-like peptide-1 and peptide YY bind to receptors in the hypothalamus, suppressing appetite
Ghrelin secretion from the stomach decreases, reducing hunger signals
Reduced spontaneous food intake creates a larger energy deficit beyond prescribed restriction
More protein in the diet causes the liver to make more receptors that remove LDL cholesterol from the blood, lowering its levels.
Dietary protein modulates hepatic SREBP-2 activity, increasing LDL receptor gene expression
Increased LDL receptor density on hepatocytes enhances clearance of LDL particles from circulation
Plasma LDL-cholesterol concentration decreases
Evidence from Studies
Supporting (1)
Community contributions welcome
High-Protein or Low Glycemic Index Diet—Which Energy-Restricted Diet Is Better to Start a Weight Loss Program?
Contradicting (0)
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Gold Standard Evidence Needed
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