Protein During a Deficit · the Muscle-Preservation Playbook

减脂期为什么必须保蛋白 · 肌肉保留策略

Place · Level 3 · Macros

标准能量赤字下 25-30% 流失是瘦组织 · 1.6-2.4 g/kg 是金标准 · 高蛋白 + 抗阻 = Longland 2016 同时减脂增肌 · 每餐 25-40 g 分 3-4 餐

Connected to · 4

cofactor · 1

Eating Less Without Going Short
A cut can economise on calories but not on protein. 1.6-2.4 g/kg is the muscle-sparing threshold: above it more of the lost weight is fat; below it muscle leaves with it.

regulates · 2

Genetics of Weight / Not Just Willpower
Losing weight triggers a whole defence that pulls it back. Lifting plus adequate protein decides how much of the loss was muscle — keep the muscle and the metabolic downshift is smaller, so the defence pushes back less hard.
Carbs & Fiber
When carbohydrate runs very low the body makes glucose out of protein (gluconeogenesis) to feed the brain. That chain is the upstream reason a cut costs you muscle — and why protein is the last thing to economise on.

contrast · 1

Weight-Loss Supplements Debunk
The thing actually shown to work in a deficit is not on the supplement shelf: enough protein plus resistance training protects muscle, the metabolic floor. The effect sizes on that shelf are not in the same league.

Why weight loss ≠ fat loss

Stop 1/4

为什么减重不等于减脂

When you lose weight, the body doesn't only burn fat. Under a standard energy deficit, roughly 25-30% of weight lost is lean tissue — including skeletal muscle, visceral protein, and water (Hall 2015). This isn't a malfunction; it's the body's default policy during energy shortage: tear down protein and fat together, because amino acids can feed gluconeogenesis for the brain, muscle contraction is metabolically expensive, and unused tissue is 'saved on'.

Why this is a problem:

RMR drops: muscle is the main consumer of resting metabolism. Losing 5 kg of muscle ≈ RMR ↓ 50-70 kcal/day. Combined with adaptive thermogenesis, the deeper the cut the lower the RMR, and the harder it gets.Strength and function decline: strength falls faster than muscle (neural drive + cross-section both lose).Rebound is harsher: body fat regenerates faster than muscle, so the regain is fat-first. Repeated cycles → progressively worse body composition (the precursor to 'sarcopenic obesity').
Longland 2016 landmark trial (McMaster, AJCN):

40 young men, 40% energy deficit (-40% TDEE) for 4 weeksAll performed high-intensity resistance + HIIT, 6 days/weekRandomised: high protein 2.4 g/kg vs control 1.2 g/kgResults:High-protein group: fat -4.8 kg, lean mass +1.2 kg (fat loss + muscle gain simultaneously)Control group: fat -3.5 kg, lean mass +0.1 kg (basically no change)Conclusion: under an extreme deficit, adequate protein + resistance training + sufficient training stimulus = lose fat and still build a little muscle
Key takeaway: muscle preservation isn't about 'how fast you lose'; it's about 'is protein enough + is there a signal the muscle can use (resistance training)'. Without those two, roughly 1/3 of the weight you drop is probably tissue you didn't want to lose.

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Educational content, not medical advice — consult a clinician.

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