Quick answer: Supplements aren’t required for intermittent fasting, since most people can meet their needs with a balanced diet in their eating window. Some find MCT oil helps with hunger and energy, a greens or superfood drink helps fill nutrient gaps, and a protein shake helps protect muscle. Whether you enter ketosis depends on fast length and how many carbs you eat.
Key takeaways
Supplements are not necessary for intermittent fasting, and many people meet their needs through food.
Some people use MCT oil, which the body turns into ketones quickly, or a protein shake for convenience, starting small to avoid stomach upset.
Longer fasts can bring on mild ketosis, and any supplement is best discussed with your provider, especially if you take medications.
Are supplements necessary?
No. Many people meet their needs through food. If you’re new to fasting, start with the basics in what is intermittent fasting.
Supplements some people use
MCT oil
Medium-chain triglycerides are absorbed quickly and converted to ketones, which may help with hunger and energy. Start small, since MCT oil can upset the stomach. Note that it contains calories.
Greens or superfood drink
Can help fill nutrient gaps when your eating window is short.
Protein shake
Useful if you exercise or struggle to get enough protein in your window. See nutritional considerations.
Let’s talk ketosis
During a fast, especially a longer one, the body may enter mild ketosis as it shifts to burning fat. If you eat a high-carb diet in your window, you may not reach ketosis. Staying in ketosis usually requires a lower-carb diet. See how keto works.
Choosing supplements safely
Discuss supplements with your provider, especially if you take medications.
Healthy aging lens
Protecting muscle with enough protein is the priority for fasting as you age; other supplements are optional.
What the research shows
Few supplements have been tested specifically during intermittent fasting, so evidence comes from related studies.
MCTs across 13 trials (Mumme 2015, meta-analysis). This review pooled 13 randomized trials with 749 adults that replaced regular long-chain fats with medium-chain triglycerides. MCTs were linked with about 0.5 kg more weight loss and about 1.5 cm less waist size, with no change in blood lipids. The authors noted that many trials were poorly reported and some showed signs of commercial bias, so the effect, while consistent, is modest.
How much protein supports muscle (Morton 2018, meta-analysis of 49 trials). This review pooled 49 randomized trials with 1,863 healthy adults doing resistance training for at least 6 weeks. Extra protein added about 0.3 kg of lean mass and 2.5 kg to one-rep max strength, and gains leveled off at a total intake of about 1.6 g of protein per kg of body weight a day. A limitation is that these were healthy adults who lifted weights, not people following keto or fasting specifically.
MCT oil vs. olive oil (St-Onge 2008, randomized trial). 49 adults with overweight used 18 to 24 g a day of either MCT oil or olive oil as part of a 16-week weight-loss program. Among the 31 who finished, the MCT group ended about 1.7 kg lighter than the olive oil group and had less trunk and abdominal fat. A limitation is the high dropout rate (18 of 49 did not finish) and the small size.
Strength of the evidence: MCT oil has small, consistent effects, and protein matters for muscle, but neither has been tested specifically as a fasting supplement.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have diabetes, take blood sugar or blood pressure medication, or have a chronic condition, or if you are pregnant, breastfeeding, underweight, or have a history of disordered eating. The same is true if fasting leaves you dizzy, shaky or exhausted, or if you want a fasting approach tailored to your health goals.
See a medical provider promptly for fainting, confusion, chest pain, a racing heartbeat, or very low blood sugar symptoms such as shaking, sweating and confusion.
Want a fasting plan that fits your health?
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Do I actually need any supplements while fasting, or can food cover my needs?
Is supplements alongside intermittent fasting a reasonable choice alongside my current medications and supplements?
Would it be worth checking any labs before I try supplements alongside intermittent fasting, or is my history enough to decide?
What would tell us that supplements alongside intermittent fasting is working well for me, and how long should we wait before reviewing it?
Frequently asked questions
Does MCT oil break a fast?
It contains calories, so technically yes, though some people use it to extend a fast.
Do I need protein shakes?
Only if you struggle to get enough protein from food.
Will I go into ketosis with 16/8 fasting?
Possibly mild ketosis, depending on your diet.
Are supplements required?
No.
Sources
- St-Pierre V, et al. Plasma Ketone and Medium Chain Fatty Acid Response in Humans Consuming Different Medium Chain Triglycerides During a Metabolic Study Day. Front Nutr 2019. PMID: 31058159. https://pmc.ncbi.nlm.nih.gov/articles/PMC6481320/
- Maher T, et al. A comparison of the satiating properties of medium-chain triglycerides and conjugated linoleic acid in participants with healthy weight and overweight or obesity. Eur J Nutr 2021. PMID: 32248292. https://pmc.ncbi.nlm.nih.gov/articles/PMC7867511/
- Morton RW, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med 2018. PMID: 28698222. https://pmc.ncbi.nlm.nih.gov/articles/PMC5867436/
- Anton SD, et al. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity (Silver Spring) 2018. PMID: 29086496. https://pmc.ncbi.nlm.nih.gov/articles/PMC5783752/
- Bauer J, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc 2013. PMID: 23867520. https://pubmed.ncbi.nlm.nih.gov/23867520/
- NIH Office of Dietary Supplements: Multivitamin/mineral Supplements
- National Institute on Aging: Research on intermittent fasting shows health benefits
- Mumme K, Stonehouse W. Effects of medium-chain triglycerides on weight loss and body composition: a meta-analysis of randomized controlled trials. J Acad Nutr Diet 2015. PMID: 25636220. https://pubmed.ncbi.nlm.nih.gov/25636220/
- Morton RW, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med 2018. PMID: 28698222. https://pubmed.ncbi.nlm.nih.gov/28698222/
- St-Onge MP, Bosarge A. Weight-loss diet that includes consumption of medium-chain triacylglycerol oil leads to a greater rate of weight and fat mass loss than does olive oil. Am J Clin Nutr 2008. PMID: 18326600. https://pubmed.ncbi.nlm.nih.gov/18326600/
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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