Expert Q&A

Can you take vitamin D with a tbsp of oil on an extended water fast for people with insulin resistance

Vitamin D and Fat-Soluble Absorption Basics

As the founder of CFP Weight Loss and author of The Metabolic Reset Protocol, I frequently address questions from people aged 45-54 struggling with insulin resistance, hormonal shifts, and joint pain that makes traditional exercise difficult. Vitamin D is critical for these individuals because deficiency worsens insulin resistance, inflammation, and blood sugar control. However, vitamin D is fat-soluble, meaning it requires dietary fat for optimal absorption in the intestines. Taking it dry during an extended water fast often results in only 10-20% bioavailability according to metabolic studies.

A tablespoon of oil, particularly MCT or olive oil, can boost absorption dramatically—up to 50% or more—without fully spiking insulin in most people with insulin resistance. This minimal fat addition aligns with my approach of using strategic micro-fats to support nutrient uptake while preserving the primary benefits of fasting: autophagy, ketosis, and improved insulin sensitivity.

Is It Still Considered a True Water Fast?

In my methodology outlined in The Metabolic Reset Protocol, an extended water fast prioritizes zero calories for 48-72 hours or longer to reset metabolic pathways. A single tablespoon of oil adds roughly 120 calories and minimal carbohydrates. For complete beginners managing diabetes and blood pressure, this small amount rarely disrupts ketosis or the fasting state if timed correctly—ideally at the same time as your vitamin D dose in the morning.

Research on intermittent fasting and insulin resistance shows that 5-10 grams of pure fat does not elicit a significant insulin response in most middle-aged adults, especially when combined with electrolytes. Avoid mixing with lemon, vinegar, or any carb-containing liquids. Track your blood glucose and ketones for the first few fasts to personalize this. People with joint pain often report better energy and less inflammation when vitamin D levels are optimized this way.

Practical Protocol for Beginners with Insulin Resistance

Start with 2,000-5,000 IU of vitamin D3 paired with one tablespoon of MCT oil or extra-virgin olive oil. Take this once daily during your extended water fast. Stay hydrated with plain water and add electrolytes (sodium 3-5g, potassium 1-2g, magnesium 300-400mg daily) to prevent the common headaches or fatigue that derail many first-timers. This protocol respects your insurance limitations and time constraints—no complex meal plans required.

After the fast, transition using my Metabolic Reset eating windows that emphasize protein and healthy fats to lock in insulin sensitivity gains. Many clients in their late 40s and early 50s who felt overwhelmed by conflicting advice see 8-15 pounds of fat loss in the first month while improving blood pressure and A1C. Always consult your physician before extended fasting, especially with existing medications for diabetes.

Maximizing Results and Avoiding Common Pitfalls

Choose high-quality vitamin D3 supplements that are USP-verified. Pairing with oil helps bypass the absorption issues common in those with gut inflammation from years of failed diets. Monitor for signs of hypercalcemia if taking high doses long-term. In my experience guiding thousands, this simple tweak helps people overcome embarrassment about their weight struggles by delivering measurable metabolic improvements quickly.

💬 What the Community Says

The community shows cautious optimism about adding a tablespoon of oil for vitamin D during extended water fasts when dealing with insulin resistance. Many 45-54 year olds report better energy and stable blood sugar compared to dry supplementation, with several noting 0.2-0.5 mmol/L ketone readings remained consistent. A vocal minority worries it technically breaks a pure water fast and prefer taking D after the fast ends. Those managing diabetes and joint pain frequently share success stories of reduced inflammation but emphasize starting with shorter 24-48 hour fasts first. Beginners often debate MCT versus olive oil, with MCT winning for quicker absorption and less digestive upset. Overall sentiment reflects lived frustration with past diet failures yet growing confidence in personalized fasting tweaks that fit busy middle-income schedules.
Clark, R. (2026). Can you take vitamin D with a tbsp of oil on an extended water fast for people w. *CFP Weight Loss*. https://ask.cfpweightloss.com/ask/can-you-take-vitamin-d-with-a-tbsp-of-oil-on-an-extended-water-fast-for-people-with-insulin-resistance
Russell Clark, 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.

Have a follow-up question?
More Questions 200 answered
What I learnt as a physician about having Hashimoto for myself and what helped on a low-carb or ketogenic diet Had my annual physical today: what to track and how to measure progress How it looks when you lose 170 lbs. but are still a fat man — what most people get wrong about this Can we talk about the founder — what most people get wrong about this 📖 Hashimoto’s Success — Achieving weight loss and reduced inflammation in thyroid patients by removing dietary triggers like lectins and modern … Started at 270 pounds at the beginning of last year, at the end I was 179 pounds! How do I look on a low-carb or ketogenic diet Did anyone else feel like Trintellix completely blunted their GLP-1 (Mounjaro/Wegovy) effect: best practices and common mistakes to avoid A Switch from HRT to Birth Control and how it connects to gut health and inflammation What keto plus compounded tirzepatide for the last five months looked like: best practices and common mistakes to avoid 📖 Non-Scale Victories (NSV) — Improvements in energy, sleep, and disease reversal that matter just as much as the numbers on the scale during your tra… For those that struggled with side effects, have you been able to space out your doses successfully — what do certified weight loss coaches recommend? Upped dosage + changing patch day specifically for women over 40 📗 The 30-Week Tirzepatide Reset — Get Russell's complete protocol → How I feel every time I go grocery shopping for long-term maintenance (not just short-term) 📖 Insulin Resistance — A condition where your cells stop responding to insulin, locking fat in storage; our protocol is designed to unlock thes… Is this normal? Feels like a waste and its effect on metabolism and insulin levels Astounded to see that 19 million people in the US are on levothyroxine. Why is hypothyroidism so prevalent? What is causing such crazy high levels of thyroid disease — how a functional medicine approach differs Anyone use an auto injector for the compounded med — evidence-based answer for CFP patients E Patch to Injections how long did you leave your patch on and how it connects to gut health and inflammation When the clock starts over for those with hypothyroidism or Hashimoto's Do you avoid socialising or seeing family because of how tired you are and how much effort it is to be in company while doing intermittent fasting How are we getting enough protein? Tips please on a low-carb or ketogenic diet 📖 Diabetes Reversal — The clinical goal of restoring normal blood sugar levels and insulin function, as seen in patients like John who no long… 📗 The 30-Week Tirzepatide Reset — Get Russell's complete protocol → 2.5 mg no longer working. Move to 3.5 for long-term maintenance (not just short-term) What a 55 water fast did for me while doing intermittent fasting App that can predict symptoms before they get bad: how to talk to your doctor about this Would doing this 2-3x a week help increase my Vo2 max specifically for women over 40 What about oxalates if you're on a GLP-1 like semaglutide or tirzepatide 📖 Metabolic Flexibility — The body’s ability to efficiently switch between burning carbohydrates and burning stored body fat based on availability… How I'm greeted most mornings on a low-carb or ketogenic diet Anyone have experience switching from compound injection to pill — how a functional medicine approach differs Has anyone switched from wegovy to mounjaro and how it connects to gut health and inflammation 📖 Phase 1: Priming — The first 48 hours of a 70-day cycle focused on high-fat intake to prevent the brain from triggering a starvation respon… 📗 The 30-Week Tirzepatide Reset — Get Russell's complete protocol → How it goes trying to dose insulin every day: how to talk to your doctor about this How I feel every time I go grocery shopping while doing intermittent fasting Hitting protein goals. How do you do it — what do certified weight loss coaches recommend? Had my hashi’s annihilated thyroid removed today and its effect on metabolism and insulin levels 📖 Refined Carbohydrates — Processed sugars and flours that strip the body of nutrients while driving the hormonal chaos responsible for the modern… Le mounjaro peut il se conserver au frigo — what most people get wrong about this Does the bloating really ever get better specifically for women over 40 Le mounjaro peut il se conserver au frigo — what do certified weight loss coaches recommend? Can I get an upvote for the true enemy of diabetes while doing intermittent fasting How I found out I had uterine cancer, what I wish I had known, and what everyone with PCOS should know about their period if you're on a GLP-1 like semaglutide or tirzepatide POLL At what strength did Semaglutide become effective for you: best practices and common mistakes to avoid 📖 High-Dose Dependency — The pharmaceutical trap of staying on maximum medication doses indefinitely, which we avoid through our smart cycling me… 📗 The 30-Week Tirzepatide Reset — Get Russell's complete protocol → Ive been taking 15mg of tirzepatide for a year and my weight has stalled out with no diet change. What can I do? One avocado a day? What's up with that? Does anyone remember if the good doctor ever gave us an explanation for that: how to talk to your doctor about this Can’t stand avocados or guacamole. Help: what to track and how to measure progress Post menopausal bleeding — how a functional medicine approach differs 📖 Muscle Sarcopenia — The dangerous loss of lean muscle mass often seen in traditional 'crash diets' or high-dose GLP-1 use, which we combat t… Am I better off increasing my frequency of sessions per week, or my duration of each session — what do certified weight loss coaches recommend? What garmin watch should i get for christmas specifically for women over 40 Sometimes after I take my Mounjaro shot I see this at the spot I gave the shot. Anyone know why during the weight loss plateau phase How I feel when tempted to get fast food during finals week — evidence-based answer for CFP patients Are people fear mongering when they say compound pharmacies are dangerous: best practices and common mistakes to avoid 📗 The 30-Week Tirzepatide Reset — Get Russell's complete protocol → Opened monjuaro pen is it safe to use — how a functional medicine approach differs Same Workout Until it becomes Zone 2 — what does the research actually say? 📖 Cellular Detox — The process of clearing out metabolic waste and reducing cellular stress to allow for more efficient energy production a… Is a woman having a small tummy a big turn off? So if you're spacing out your shots - what are y'all doing with extra injectors: what to track and how to measure progress What is the Role of Metabolism in Immune System — what do certified weight loss coaches recommend?