Fasting & Schedules·5 min read·September 2026

The Intermittent Fasting Window Solver: 16:8 and 18:6 Meal Allocation

Compressing daily caloric requirements into 2 or 3 feeding slots without digestive distress.

Combining intermittent fasting (IF) with a ketogenic diet is one of the most effective interventions for lowering fasting insulin, elevating autophagy, and accelerating fat loss. However, packing 1,800 calories and 130g of protein into a compressed 6- or 8-hour window introduces severe digestive and macro-budgeting hurdles.

1. The Two-Meal Volumetric Gastric Constraint

On a standard 16:8 schedule, most dieters eliminate breakfast, leaving only lunch and dinner. Consuming 65g of protein and 70g of dietary fat in a single sitting requires substantial digestive capacity.

If a meal is too voluminous, gastric emptying slows excessively, leading to postprandial lethargy, reflux, and bloating. A mathematical meal planner must balance energy density against stomach volume.

Compressing 1,800 kcal into two meals requires balancing energy density with digestive enzyme capacity to avoid sluggish gastric transit.

2. The 40/60 Asymmetric Caloric Allocation Rule

Instead of splitting macros 50/50 between the two feeding slots, Repast utilizes an asymmetric 40/60 allocation. Meal 1 (the fast-breaker at 12:00 PM) delivers 40% of daily calories, featuring easily digestible proteins like wild salmon, eggs, and tender greens.

Meal 2 (the dinner anchor at 7:00 PM) claims 60% of daily calories, incorporating dense cuts like beef chuck or roasted chicken with cruciferous vegetables, providing sustained satiety throughout the overnight fast.

3. Circadian Fasting Alignment & Overnight Recovery

Fasting windows should respect human circadian biology. Peripheral clocks in the liver and pancreas are most insulin-sensitive during daylight hours. Ending your feeding window at 7:00 PM or 8:00 PM allows core body temperature to drop naturally for restorative Stage 4 slow-wave sleep.

Drinking water, black coffee, or plain mineral water with electrolytes during the 16-hour fasting window preserves hydration without breaking autophagy or elevating serum insulin.

KEY TAKEAWAY

Break your fast with a lighter 40% meal, anchor dinner with 60% of daily calories, and align your feeding window with daylight hours.

FASTING SCHEDULE SYNC

Synchronize your meal slots with your fasting timer.

Repast re-solves macro distributions for 16:8, 18:6, or 20:4 schedules, ensuring all nutrients fit into your feeding window.

Configure your fasting window on iPhone