In men with overweight or obesity, eating 0.9 grams of protein per kilogram of body weight per day for five weeks does not change resting metabolic rate, the ratio of oxygen to carbon dioxide exchanged during breathing, or the levels of proteins involved in mitochondrial energy production in muscle.
See the scientific wording
In men with overweight or obesity, a dietary protein intake of 0.9 g/kg/day for five weeks has no significant effect on resting metabolic rate, respiratory exchange ratio, or skeletal muscle mitochondrial oxidative phosphorylation protein content.
Very strong evidence
Randomized trialsOne good-quality study supports this claim.
What the research says
1 study reviewedSupporting (1)
Randomized Controlled TrialHuman2026
When overweight men ate less protein and more carbs but kept eating the same total calories, their bodies didn’t burn more or less energy at rest, and the energy-making parts in their muscles stayed the same — even though they lost some fat.
Contradicting (0)
No contradicting studies found yet
That doesn't mean it's settled — it just means no study has tested the opposite.
Quality-weighted scoring: we follow the GRADE framework — each study is rated High, Moderate, Low, or Very Low based on study design, methodology rigor, and risk of bias. A single high-quality RCT can outweigh several weaker observational studies.
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When men eat less protein but the same calories, their muscles break down less protein and burn fewer amino acids, so the amount of protein building blocks in the blood stays steady. The liver releases more of a hormone, but the tissues that respond to it do not change their response, so the body does not burn more calories at rest. Because calories and fuel mix stay the same, the energy-making parts in muscle stay the same too.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting study
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In men with overweight or obesity, eating 0.9 grams of protein per kilogram of body weight per day for five weeks does not change resting metabolic rate, the ratio of oxygen to carbon dioxide exchanged during breathing, or the levels of proteins involved in mitochondrial energy production in muscle.
Mechanism
1 studyEating less protein while keeping calories the same makes muscles break down less protein and burn fewer amino acids, so the blood keeps a steady supply of protein building blocks. The liver releases more of a hormone, but the tissues that respond to it do not change, so the body does not burn more calories at rest. Because the calorie level and fuel mix stay the same, the energy-making parts in muscle also stay the same.
When men eat less protein but the same calories, their muscles break down less protein and burn fewer amino acids, so the amount of protein building blocks in the blood stays steady. The liver releases more of a hormone, but the tissues that respond to it do not change their response, so the body does not burn more calories at rest. Because calories and fuel mix stay the same, the energy-making parts in muscle stay the same too.
Dietary protein intake decreases, lowering the supply of amino acids entering circulation.
Amino acid oxidation decreases, shown by lower plasma urea concentrations.
Muscle protein breakdown decreases to conserve amino acids, shown by stable plasma 3-methylhistidine.
Total and individual plasma amino acid concentrations remain stable, preserving the amino acid pool.
The liver increases secretion of fibroblast growth factor 21 (FGF21) into the bloodstream.
FGF21 target tissues show unchanged FGFR1c/β-klotho receptor expression and unchanged ERK1/2 phosphorylation, so FGF21 does not activate thermogenic signaling.
Resting metabolic rate remains unchanged because no thermogenic signaling is activated and amino acid conservation prevents loss of lean body mass.
The respiratory exchange ratio remains unchanged because isocaloric replacement of protein with carbohydrate does not shift the balance of carbohydrate versus fat oxidation.
Skeletal muscle mitochondrial oxidative phosphorylation protein content remains unchanged because amino acid availability is preserved and no mitochondrial remodeling signal is triggered.
Evidence from Studies
Supporting (1)
Community contributions welcome
Dietary Protein Reduction During Isocaloric Conditions Reduces Body Weight in Men With Overweight or Obesity.
When overweight men ate less protein and more carbs but kept eating the same total calories, their bodies didn’t burn more or less energy at rest, and the energy-making parts in their muscles stayed the same — even though they lost some fat.
Contradicting (0)
Community contributions welcome
Score Breakdown
No multi-axis breakdown available yet. The overall Pro / Against score above is the best signal.
- No clinical evidence is available; the score reflects mechanistic plausibility only.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Systematic Review of Low-Protein Diets (0.9 g/kg/day) on Metabolic Rate and Muscle Mitochondrial Proteins in Overweight and Obese Men
Population: Men with overweight or obesity; Intervention: Dietary protein at 0.9 g/kg/day for five weeks; Comparator: Higher protein intake (e.g., 1.6 g/kg/day) or habitual intake; Outcomes: Resting metabolic rate, respiratory exchange ratio, skeletal muscle mitochondrial oxidative phosphorylation protein content; Duration: Five weeks.
Double-Blind Randomized Controlled Trial of 0.9 g/kg/day vs. 1.6 g/kg/day Protein Intake on Muscle Mitochondrial Proteins in Overweight Men
Population: Men with overweight or obesity (n≥50); Intervention: 0.9 g/kg/day protein; Comparator: 1.6 g/kg/day protein; Outcomes: Resting metabolic rate (indirect calorimetry), respiratory exchange ratio, mitochondrial oxidative phosphorylation protein content (muscle biopsy); Duration: Five weeks; Design: Randomized, double-blind, isocaloric, controlled feeding.
Prospective Cohort Study of Protein Intake and Metabolic Outcomes in Overweight Men Over Five Weeks
Population: Men with overweight or obesity; Intervention: Controlled dietary protein at 0.9 g/kg/day for five weeks; Comparator: Higher protein intake group; Outcomes: Resting metabolic rate, respiratory exchange ratio, mitochondrial protein content; Duration: Five weeks; Design: Prospective, with baseline and endpoint measurements.
Cross-Sectional Analysis of Protein Intake and Mitochondrial Protein Content in Overweight Men
Population: Men with overweight or obesity; Intervention: None (observational); Comparator: Groups categorized by protein intake (e.g., ≤0.9 g/kg/day vs. >1.0 g/kg/day); Outcomes: Resting metabolic rate, respiratory exchange ratio, mitochondrial protein content; Duration: Single time point.
In Vitro Study of Low Protein Conditions on Mitochondrial Oxidative Phosphorylation Protein Expression in Human Myotubes
Population: Human skeletal muscle myotubes derived from overweight/obese donors; Intervention: Culture medium with low leucine and total amino acids mimicking 0.9 g/kg/day intake; Comparator: Normal amino acid concentration; Outcomes: Expression of oxidative phosphorylation complex proteins; Duration: Five days.