Expert Q&A

Starting my second extended fast tomorrow. Hoping for 12 days or maybe do another 42 — what most people get wrong about this

Understanding Extended Fasting Basics

I've guided thousands through extended fasting protocols after they failed every conventional diet. Extended fasting means going beyond 48 hours without calories, typically 5-21 days or longer, relying on stored body fat for energy. For beginners aged 45-54 dealing with hormonal shifts, joint pain, and conditions like diabetes or high blood pressure, the key is starting conservatively at 12 days before considering a 42-day fast. Most rush in without preparation, leading to frustration and rebound weight gain.

Common Mistakes That Sabotage Results

The biggest error is ignoring electrolyte balance. During extended fasting, your body dumps sodium, potassium, and magnesium, causing headaches, cramps, and fatigue. Supplement with 4-5g sodium, 3-4g potassium, and 400mg magnesium daily. Another frequent mistake is poor hydration—aim for 3-4 liters of water plus herbal teas. Many overlook joint pain management; without carbs, inflammation can spike initially. Use gentle movement like walking 20-30 minutes daily and consider bone broth (if doing a modified fast) for collagen support. Hormonal changes in perimenopause or andropause make fat loss harder, so track thyroid and cortisol levels with your doctor before starting.

Safety Protocols for 12 to 42-Day Fasts

Never attempt a 42-day fast without medical supervision, especially with diabetes or blood pressure meds—insulin and BP drugs often need immediate adjustment to prevent lows. Break your fast gradually over 3-5 days with bone broth, then soft foods to avoid refeeding syndrome, a dangerous shift in fluids and electrolytes that can cause heart issues. In my book The Fasting Reset, I detail a step-by-step refeeding plan that has helped hundreds avoid this. Monitor blood glucose and ketones daily; target 0.5-3.0 mmol/L ketones for safe fat burning. If dizziness or rapid heartbeat occurs, stop immediately.

Long-Term Success After the Fast

What most get wrong is treating fasting as a one-off instead of a reset. After 12 days, transition to a low-carb Mediterranean-style plan with 16:8 intermittent fasting windows to maintain losses. Expect 1-2 pounds per day initially, slowing to 0.5 pounds as you near 42 days. Address the emotional side—journaling cravings prevents bingeing. Insurance rarely covers programs, so focus on affordable bloodwork and at-home monitoring. With proper execution, extended fasting can reverse metabolic slowdown from past yo-yo diets and improve joint mobility as inflammation drops 30-50% by day 10. Start tomorrow prepared, not hopeful.

💬 What the Community Says

The community shows a mix of excitement and caution around extended fasting. Many in their late 40s and early 50s share success stories of losing 15-25 pounds in 12-day fasts, especially after years of failed diets, but complain about severe fatigue and joint aches in the first week. A vocal group debates the safety of 42-day fasts, with some reporting improved blood sugar and blood pressure while others warn of hair loss, muscle cramps, and scary refeeding experiences. Beginners often feel overwhelmed by conflicting advice on electrolytes and supplements, leading to early quits. Those managing diabetes emphasize doctor approval, noting insurance rarely helps. Overall, practitioners appreciate the mental clarity that hits around day 5 but stress the need for realistic expectations—most agree it's not sustainable long-term without lifestyle changes afterward.
Cite this answer
Clark, R. (2026). Starting my second extended fast tomorrow. Hoping for 12 days or maybe do anothe. *CFP Weight Loss*. https://ask.cfpweightloss.com/ask/starting-my-second-extended-fast-tomorrow-hoping-for-12-days-or-maybe-do-another-42-what-most-people-get-wrong-about-this
Russell Clark, FNP-C, APRN, FNP-C, APRN
About the Author

Russell Clark, FNP-C, APRN, is the founder of CFP Weight Loss in Nashville and CFP Fit Now telehealth. Over 35 years in healthcare — Army Nurse Reserves, Level 1 trauma ER, hospitalist — he developed a 30-week protocol integrating real foods, detox, and low-dose tirzepatide cycling that has helped hundreds of patients lose 30–90 pounds. He and his wife Anne-Marie lost a combined 275 pounds using the same protocol.

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