Printable Fasting Journal

de Cabo and Mattson's review in NEJM (2019, 381(26)) summarized that intermittent fasting may improve metabolic markers, blood pressure, and insulin sensitivity. In head-to-head trials, weight loss has generally been similar to ordinary calorie restriction rather than greater. Effects are individual — track your fasting hours, energy, and mental clarity to build personal evidence. Consult your physician before starting, especially with chronic conditions.

Common protocols: 16:8 (16-hour fast, 8-hour eating window — most popular), 18:6 or 20:4 (extended daily fasts), 5:2 (5 normal days + 2 reduced-calorie days, often around 500–600 kcal), 24-hour fasts 1–2 times weekly, alternate-day fasting. Document yours in the fasting protocol field. Compare energy and mental clarity ratings across protocols over 4–8 weeks to find what works for your physiology and lifestyle.

de Cabo & Mattson (NEJM, 2019) note that hunger, irritability and trouble concentrating are common at the start and usually ease within about a month. Your hunger level and mental clarity ratings show your own curve across those weeks. The challenges prompt captures early difficulties (irritability, headaches, fatigue) that usually resolve. Persistent severe symptoms beyond 4 weeks warrant reassessment with your physician — IF is not appropriate for everyone.

Intermittent fasting is generally not advised for people with type 1 diabetes (hypoglycemia risk), during pregnancy or breastfeeding, with a history of eating disorders, when underweight (BMI <18.5), for adolescents and children, or with certain medications (insulin, sulfonylureas). The ADA Standards of Care (2024) stress that people with diabetes on glucose-lowering medication need physician oversight to adjust doses. Fasting is strongly discouraged for anyone with a history of anorexia, bulimia, or binge eating disorder; talk to your treatment team before changing how you eat.

Generally: plain water, black coffee, plain tea, herbal teas — they contain virtually no calories and are widely accepted as keeping the fast. Anything with calories (cream, sugar, milk, juice) breaks the fast. The what broke the fast prompt tracks when you ate, which matters more than rigid purity. Hydration during fasts is critical — dehydration mimics fasting fatigue symptoms.

Track 4+ weeks of consistent data. Objective markers include weight, waist circumference, fasting glucose, and blood pressure (measured separately). Subjective markers in this journal: energy ratings stabilize or improve, mental clarity rises, hunger level drops from baseline. If markers worsen or stay poor across 6–8 weeks, the protocol may not suit your physiology — try a different approach or consult a registered dietitian.

IF restricts when you eat; calorie restriction restricts how much. Both can produce weight loss; de Cabo & Mattson (NEJM, 2019, 381(26)) describe possible additional metabolic effects of fasting-induced cellular processes (autophagy, ketosis), though human evidence is preliminary. The fasting hours field tracks the time dimension; for a direct comparison, also note eating-window calories in the insights lines.

Red flags: persistent dizziness, fainting, severe weakness, irregular heartbeat, mood disturbance, hair loss, missed menstrual periods, or worsening of any chronic condition. Track these in the challenges prompt — patterns that point to physiological stress warrant immediate cessation and physician evaluation. Disordered eating thoughts emerging during IF (binge urges, food preoccupation, body image obsession) require consultation with a mental health professional.