Does MCT Oil Break a Fast?

Quick answer: Yes, in the calorie sense. One tablespoon of MCT oil has about 100 to 130 calories of pure fat, depending on the brand. A “bulletproof” or butter coffee with a tablespoon of butter and a tablespoon of MCT oil has about 200 to 235 calories, which is closer to a small meal than a fasting drink. MCT oil has no carbs, so it won’t stop ketosis, but it isn’t allowed on a strict fast or before a fasting blood test.

Try it yourself: With an 18:6 schedule and an eating window of 12 PM to 6 PM, a butter coffee at 8 AM adds 200 or more calories, so your eating day really begins at 8 AM, not noon. Drink the coffee black in the morning and stir the MCT oil into your noon meal instead. Check your own timing with the intermittent fasting calculator.

Calories in MCT Oil, Butter and Fasting Coffee

Coffee, butter and coconut oil values are from USDA FoodData Central. MCT oil labels vary between about 100 and 130 calories per tablespoon, so check yours.

Which Kind of Fast Are You Doing?

Weight-loss intermittent fasting

Intermittent fasting helps many people mainly by shrinking the hours they eat, which makes it easier to eat less. A 200-calorie coffee every morning still counts toward your day. If it keeps you full until lunch and you eat less overall, it may fit your plan, but it’s no longer a fast. Run your numbers in the calorie deficit calculator.

Ketosis

This is where MCT oil gets its fan base. MCTs are absorbed quickly and the liver turns part of them into ketones. In a study by St-Pierre and colleagues (2019), C8 (caprylic acid) oil was about three times more ketogenic than C10 and about six times more than C12. The ketone response was roughly twice as high when the oil was taken without a meal. So MCT oil supports ketosis, but higher ketones don’t mean you’re still fasting, and they don’t guarantee fat loss.

Autophagy

Autophagy gets a lot of attention online, but the strong data come mostly from animals and cell studies. Researchers have no simple blood test for it in humans, and MCT oil has never been tested for its effect on it. If autophagy is your main reason for fasting, the cautious choice is to keep the fasting window calorie-free.

Fasting blood tests

Lipid panels and fasting glucose tests are designed to measure your blood in a no-food state. MedlinePlus (from the National Library of Medicine) lists plain water as the only drink to have while fasting for bloodwork, typically for 8 to 12 hours. A fat-heavy coffee before a cholesterol check is the opposite of that, so wait until after the draw.

Is Butter Coffee a Good Idea After 40?

A few things are worth weighing in midlife:

• Cholesterol: In the SWAN study of 1,054 women, LDL (“bad”) cholesterol rose substantially in the year before and the year after the final menstrual period (Matthews et al., 2009). A tablespoon of butter has about 7 g of saturated fat, and MCT oil is labeled as all saturated fat. If your LDL is creeping up, ask your doctor whether a daily butter coffee makes sense.
• Calories add up: A 200 to 235 calorie coffee every morning is about 1,400 to 1,650 calories a week. That can quietly cancel the deficit you’re fasting to create.
• Protein: Butter coffee has almost none. Many women over 40 do better breaking a fast with a protein-rich meal.

Hitting a plateau? These are the usual culprits in intermittent fasting during menopause when you’re not losing weight.

Better Ways to Use MCT Oil

• Use it to break your fast. Add it to the first coffee or smoothie of your eating window.
• Start small. A teaspoon is a gentler start than a full tablespoon.
• Count it. Log it like any other oil.
• During the fast, keep it simple. Black coffee, plain tea and water carry no meaningful calories.

Frequently Asked Questions

Does bulletproof coffee break a fast?

Yes. With a tablespoon each of butter and MCT oil, it has about 200 to 235 calories, which ends a fast for weight-loss purposes.

Does MCT oil kick you out of ketosis?

No. It’s pure fat with no carbs, and MCTs can raise blood ketones.

Does MCT oil break autophagy?

It hasn’t been studied in people, so the honest answer is unknown.

Does a teaspoon of MCT oil break a fast?

A teaspoon is about a third of a tablespoon, or roughly 35 to 45 calories. That’s still more than most people allow during a fast. See how many calories break a fast.

Does MCT oil powder break a fast?

Yes. Powders also contain calories, and some add fillers or carbs, so check the label.

Does bone broth break a fast?

Yes, it has calories and protein, though some people use it on modified fasts. See does bone broth break a fast.

Related Tools

• Intermittent Fasting Calculator
• Calorie Deficit Calculator
• Does Black Coffee Break a Fast?

This article is for general information only and is not medical advice. Read our Medical Disclaimer.

Sources

• USDA FoodData Central: Butter, salted (FDC 173410); Oil, coconut (FDC 171412); Coffee, brewed (FDC 171890) — https://fdc.nal.usda.gov/
• 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 — https://pmc.ncbi.nlm.nih.gov/articles/PMC6481320/
• Matthews KA, et al. Are changes in cardiovascular disease risk factors in midlife women due to chronological aging or to the menopausal transition? J Am Coll Cardiol. 2009 — https://pubmed.ncbi.nlm.nih.gov/20082925/
• MedlinePlus (NIH): Fasting for a Blood Test — https://medlineplus.gov/lab-tests/fasting-for-a-blood-test