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Fat, not muscle
In the landmark crossover trial, dieters sleeping 5.5 h lost 55% less fat and 60% more lean mass than the same people sleeping 8.5 h on identical calories.
For iPhone · works with or without Apple Watch
Sleep is your most underrated fat‑loss tool.
Same diet, 5.5 h vs 8.5 h of sleep: 55% less fat lost. SleepShred tracks how you sleep, finds out why, screens for the sleep disorders most people never get diagnosed with — and shows you the paper behind every claim.
Free · No account · Your data stays on your iPhone
55%
less fat lost on the same diet when sleeping 5.5 h instead of 8.5 h
Nedeltcheva 2010 · Ann Intern Med−270 kcal
per day, eaten spontaneously after sleeping ~1.2 h more — no diet advice given
Tasali 2022 · JAMA Intern Med+24%
appetite after two nights of 4 h sleep, driven by ghrelin up and leptin down
Spiegel 2004 · Ann Intern MedWhy sleep decides what you lose
Losing fat is a calorie deficit — categorically simple, practically hard. What most plans ignore is that sleep decides whether the deficit comes out of fat or muscle, and how hungry you'll be while you do it. Every number below links to the study.
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Hunger hormones
Two nights of short sleep raise ghrelin, lower leptin and increase appetite ~24%, especially for calorie-dense carbs. Sleep-restricted adults gain ~1 kg in five days, mostly from late-night eating.
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Insulin & muscle
Four nights of 4.5 h sleep made fat cells ~30% less insulin-sensitive; five nights of 4 h cut muscle protein synthesis ~18%.
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More sleep, less eating
Extending sleep by ~1.2 h in a real-life RCT reduced intake by ~270 kcal/day with no dietary instruction at all.
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Caffeine timing
400 mg six hours before bed still cost more than an hour of sleep — while subjects didn't notice. A coffee needs ~8.8 h to clear its effect. SleepShred computes your personal cutoff.
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The hidden epidemic
~936 million adults have obstructive sleep apnea; the vast majority are undiagnosed. Regularity of sleep predicts mortality better than duration. Both are one-minute screens in the app.
Track how you sleep. Find out why.
Built from Dr Andy Galpin's principles: how you feel is the primary metric, trust total sleep time (not sleep scores), change one thing at a time.
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Nights
Total sleep, efficiency, resting HR, SpO₂, HRV — from Apple Health or a 20-second manual entry. A 1–5 morning rating leads every day.
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Days
Caffeine doses with a personal cutoff, alcohol, meals, screens, morning light, movement (the 5·4·3·2·1 rule), naps, energy, weight & waist, supplements.
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Factors
Nights after each behaviour vs without: alcohol −27 min, morning light +16 min… your own data, no guesswork.
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Screen
STOP-BANG, Epworth, Insomnia Severity Index, restless-legs criteria and chronotype — validated, scored, with a next-step ladder and a doctor script.
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Lab
One-variable experiments (temperature, kiwis, magnesium, separate sheets…) with baseline vs intervention, effect size and verdict. Plus an environment audit and a bedroom noise meter.
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Learn
29 cards distilled from the episode and a library of 98 peer-reviewed papers, linked from every claim in the app.
How it works
Twenty seconds a day
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Rate the night
One tap each morning: how do you feel, 1–5. That subjective signal outranks any wearable score.
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Log the day
Tap presets for coffee, meals, screens, workouts, weight. Or let Apple Health fill it in.
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See what moves the needle
Trends pairs each day with the night that follows and your weekly weight change with your weekly sleep.
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Test it, keep it, stack it
Turn a promising factor into a Lab experiment. Keep the wins, drop the rest — resilience, not a 12-step routine.
The 5·4·3·2·1 rule
Galpin's fat-loss movement rule, tracked weekly in the app: nutrition drives the deficit, exercise keeps the fat off, sleep decides what you lose.
5days active
4structured sessions
3sweaty sessions
2strength sessions
1very-high heart-rate effort
Sleek, dark, honest
Questions
Do I need an Apple Watch?
No. Everything works with a 20-second manual entry each morning. If you connect Apple Health, sleep, heart data, caffeine, weight and steps flow in automatically.
Is this a diet app?
No. SleepShred doesn't count calories for you (though you can log them). It shows how sleep, caffeine, alcohol, meals, screens and training change your sleep — and how your sleep changes your weight.
Is it medical advice?
No. The screening questionnaires are validated instruments, but a score is a screen, not a diagnosis. Take an elevated score to your doctor and ask about a sleep study.
Where does my data go?
Nowhere. It stays on your iPhone. No account, no analytics, export to CSV any time.
Where does the science come from?
The app was built from Dr Andy Galpin's sleep and fat-loss segment on The Diary Of A CEO, cross-referenced with 98 peer-reviewed papers you can open from inside the app.
Sleep better tonight. Shred what you actually want to shred.
Free on the App Store. No account. Your data stays on your iPhone.
Download on the App Store