Find your optimal daily eating window based on your wake time, chronotype, and schedule. Backed by time-restricted eating research from the Salk Institute.
BiteKit helps you log meals with timestamps so you can see exactly when you're eating — and how well it aligns with your circadian rhythm.
Time-restricted eating (TRE) — also called circadian eating — means consuming all daily calories within a consistent 8-12 hour window, ideally aligned with daylight hours. Unlike intermittent fasting protocols focused on total fasting duration, TRE emphasizes the timing of the eating window relative to your internal biological clock.
Dr. Satchidananda Panda and his team at the Salk Institute have conducted landmark research showing that mice fed the same high-fat diet but restricted to an 8-hour window weigh significantly less and have better metabolic health than mice allowed to eat at any time — even though total calories are identical.
Within 30-60 minutes of waking, cortisol surges as part of the cortisol awakening response (CAR). This cortisol spike serves as a biological alarm clock, mobilizing energy stores and synchronizing peripheral clocks in the liver, pancreas, and intestines with the central circadian clock in the brain (the suprachiasmatic nucleus).
Eating immediately after waking blunts this cortisol peak and can desynchronize peripheral clocks. Waiting 1-2 hours before your first meal allows cortisol to naturally decline and your body to prepare optimal insulin signaling for the incoming meal.
Insulin sensitivity follows a diurnal rhythm — it is highest in the morning and progressively decreases throughout the day. The same 500-calorie meal consumed at 8 AM produces a smaller, shorter insulin spike than the same meal consumed at 8 PM. Chronobiology research shows that eating earlier:
Chronotype describes your genetically influenced preference for sleep-wake timing. About 20-25% of people are early birds, 55-60% are intermediate, and 20-25% are night owls. Your chronotype is controlled partly by variations in clock genes (PER2, PER3, CLOCK) and shifts with age — teenagers are naturally night owls, while adults trend earlier.
Because a night owl's circadian phase is naturally delayed by 1-2 hours relative to an early bird's, forcing them to eat at the same clock time creates internal circadian misalignment. This calculator adjusts your optimal eating window start and end times based on your chronotype so you get the metabolic benefits of circadian alignment without fighting your biology.
The pattern of distributing more calories earlier in the day (front-loading) and fewer calories at dinner is associated with significantly better metabolic outcomes. A 2013 study by Garaulet et al. found that eating the main meal before 3 PM resulted in greater weight loss than eating it after 3 PM — even with identical total calories and macronutrients.
This calculator uses a 20/40/25/15 distribution: 20% at breakfast, 40% at lunch, 25% at a mid-afternoon snack, and only 15% at dinner. This front-loads 60% of calories into the first half of the eating window when insulin sensitivity and digestive enzyme activity are highest.
Night shift workers are at significantly higher risk for obesity, type 2 diabetes, cardiovascular disease, and gastrointestinal issues due to chronic circadian misalignment. Research suggests the best strategy is to:
A circadian eating window is the daily time period during which you consume all your calories, timed to align with your body's internal biological clock. Research shows that eating within an 8-12 hour window — especially earlier in the day — significantly improves insulin sensitivity, metabolism, and sleep quality.
Chronotype is your genetically influenced sleep-wake preference. Early birds have an advanced circadian phase, so their optimal window starts and ends earlier. Night owls have a delayed phase — their optimal window shifts 1-2 hours later. Eating against your chronotype creates circadian misalignment, which has metabolic consequences similar to jet lag.
Cortisol peaks 30-60 minutes after waking as a natural biological signal. Eating immediately blunts this peak and can desynchronize your metabolic clocks. Waiting 1-2 hours allows cortisol to complete its role in readying your metabolism before you add the insulin response of a meal.
They overlap but differ in emphasis. Intermittent fasting (like 16:8) focuses on the fasting duration and often allows flexibility in when the eating window occurs. Time-restricted eating specifically emphasizes aligning the eating window with daylight and biological rhythms — the timing relative to your circadian clock matters as much as the window length.
Yes. For shift workers, consistency of eating window relative to your sleep schedule is more important than the clock time. This calculator's night shift mode adjusts recommendations relative to your personal sleep-wake cycle rather than the solar cycle.
Start with what is achievable. Even a 1-hour shift toward the optimal window has measurable metabolic benefits. Gradually adjust your eating times by 15-30 minutes every few days rather than making a sudden change.