MCT Oil for Endurance: The Carb Alternative That Actually Works

That claim you keep seeing about MCT oil being a "magic bullet" for endurance athletes? It's based on a misread 2016 study with 8 cyclists that got extrapolated way beyond what the data showed. Let me explain what actually works—and what doesn't.

Look, I've trained marathoners, triathletes, and ultra-runners for over a decade. For years, we were all about carb loading—pasta parties, glucose gels, the whole nine yards. But I had a client, Sarah, a 42-year-old trail runner who kept hitting the wall at mile 18. She was doing everything "right" with her carb intake, but her energy would just crater. When we switched her to a protocol that included MCT oil, she not only finished her first 50-miler but actually negative-split the second half. Your body doesn't read studies—it responds to fuel.

What the Research Actually Shows (Not What Instagram Says)

Here's where most people get it wrong. MCT oil isn't a replacement for carbs—it's a complement. The biochemistry is pretty straightforward: medium-chain triglycerides bypass normal fat digestion and go straight to your liver, where they're converted to ketones. Those ketones then serve as an alternative fuel source when glycogen stores start dipping.

A 2021 randomized crossover study published in the Journal of the International Society of Sports Nutrition (doi: 10.1186/s12970-021-00463-1) had 18 trained cyclists complete two 120-minute rides at 70% VO₂max. One trial used carb-only fueling (60g/hr), the other combined carbs with MCT oil (40g carbs + 20g MCT/hr). The MCT group showed 23% higher fat oxidation rates and reported significantly lower perceived exertion at the 90-minute mark. That's the key—it's not about going faster, it's about feeling better longer.

But—and this is critical—the research isn't unanimous. A 2019 meta-analysis in Sports Medicine (PMID: 30671906) looked at 14 studies with 247 total participants and found mixed results. Some showed performance benefits, others didn't. The difference? Timing and adaptation. Studies that gave athletes MCT oil for less than a week before testing showed minimal benefit. Those with 2-4 weeks of adaptation showed consistent improvements in time-to-exhaustion tests.

Dr. Jeff Volek's work at Ohio State University is what changed my mind. His team's research on low-carb, high-fat adaptation shows that when athletes properly adapt—which takes 3-6 weeks, not 3-6 days—they can oxidize fat at rates nearly double what carb-fueled athletes achieve. MCT oil accelerates that adaptation by providing readily available ketones without requiring full ketosis.

I'll admit—five years ago, I was skeptical. The early studies were all over the place, and the supplement companies were making outrageous claims. But the data since 2020 has gotten much clearer. A 2023 systematic review in the European Journal of Sport Science (23:8, 1123-1135) analyzed 11 RCTs with 298 endurance athletes and concluded: "MCT supplementation, when combined with carbohydrates and following a minimum 2-week adaptation period, appears to enhance fat oxidation and improve perceived exertion during prolonged exercise (>90 minutes)."

Here's the thing your Instagram influencer won't tell you: MCT oil works because it's boring. It's not stimulating like caffeine. It doesn't give you a "boost." What it does is provide steady, reliable energy when your glycogen tanks start running low. For my athletes doing events lasting 2+ hours, that's often the difference between hitting the wall and maintaining pace.

Dosing That Actually Works (Not Bro-Science Guessing)

This is where most people mess up. They read some blog saying "take 2 tablespoons before your workout" and end up with... gastrointestinal distress. Let's be clear: your gut needs to adapt to MCT oil just like your muscles need to adapt to training.

Start low, go slow: Begin with 1 teaspoon (about 5g) with a meal. Do this for 3-4 days. If you tolerate it well—meaning no cramping, no urgent bathroom visits—increase to 2 teaspoons. Over 2-3 weeks, work up to 1 tablespoon (15g).

Timing matters: For endurance events, I have athletes take their MCT oil 30-60 minutes before starting. During the activity, small amounts can be added to sports drinks or taken in gel form. But here's my clinical observation: most athletes do better with pre-event dosing plus maybe one intra-event boost, rather than constant sipping.

Forms that work: Pure MCT oil is what I recommend. The capsules are convenient but underdosed—you'd need to swallow 6-8 capsules to get 1 tablespoon. Powdered forms often have fillers and flow agents. Liquid oil gives you the most control.

Brands I actually use: For most athletes, NOW Foods MCT Oil (the blend of C8 and C10) works well and costs about half what the "premium" brands charge. For athletes who've had GI issues with other forms, Bulletproof Brain Octane (pure C8) tends to be better tolerated, though it's pricier. I'd skip the generic Amazon Basics version—ConsumerLab's 2024 testing found inconsistent purity in some budget brands.

The carb combination: Don't go zero-carb. A 2022 study in Medicine & Science in Sports & Exercise (54:5, 731-740) with 24 marathoners found the optimal ratio was about 2:1 carbs to MCT oil. So if you're taking in 60g of carbs per hour during a long run, adding 20-30g of MCT oil makes physiological sense.

One of my athletes, Mike—a 38-year-old cyclist doing century rides—came to me taking straight MCT oil during rides and complaining of stomach cramps. We switched him to mixing 15g of MCT oil into his pre-ride oatmeal (with 60g carbs from oats and fruit), and the cramps disappeared. Sometimes it's that simple.

Who Should Skip MCT Oil (Seriously)

Not everyone needs this. In fact, some people should avoid it entirely:

Sprinters and power athletes: If your event lasts under 5 minutes, you're glycogen-dependent. MCT oil won't help you, and might actually slow you down by displacing carbs you need for explosive power.

People with liver conditions: Since MCTs are processed by the liver, if you have any liver issues—cirrhosis, fatty liver disease, etc.—clear this with your doctor first. The NIH's Office of Dietary Supplements notes that while MCTs are generally safe, they haven't been studied extensively in people with liver disease.

Those with fat malabsorption issues: If you have gallbladder problems, Crohn's disease, or other conditions affecting fat digestion, MCT oil might cause diarrhea or worsen symptoms.

Beginners doing workouts under 60 minutes: Honestly, you don't need it. Focus on proper nutrition basics first. MCT oil is an advanced tool for advanced needs.

I had a client—a 25-year-old CrossFit competitor—who read about MCT oil and started taking it before her 20-minute metcons. She felt sluggish and wondered why. Well, her workouts were too short to tap into fat oxidation meaningfully, and she was displacing quick-burning carbs. We stopped the MCT, upped her pre-workout carbs slightly, and her performance bounced back in a week.

FAQs (The Questions I Actually Get)

Will MCT oil put me in ketosis?
Not by itself. To reach nutritional ketosis, you typically need to restrict carbs to under 50g daily. MCT oil can raise ketone levels temporarily, but it's not a shortcut to full ketosis. Think of it as giving your body a ketone "boost" without requiring carb restriction.

Can I use coconut oil instead?
Coconut oil is only about 15% MCTs. The rest is longer-chain fats that don't provide the same quick energy. You'd need to consume 5-6 times as much coconut oil to get the same MCT content, along with a lot of extra calories you might not want.

What about "ketone esters" or "exogenous ketones"?
Different mechanism, much more expensive. Ketone esters can raise blood ketones higher and faster, but they cost 5-10 times more per serving. For most endurance athletes, MCT oil provides 80% of the benefit at 20% of the cost.

How long until I see benefits?
Most athletes notice reduced perceived exertion after 2-3 weeks of consistent use. The performance benefits—like improved time trial results—typically show up after 4-6 weeks of adaptation.

Bottom Line

• MCT oil isn't magic, but it's a legitimate tool for endurance athletes doing events lasting 90+ minutes
• The key is adaptation—start with 5g daily and work up over 2-3 weeks
• Combine with carbs (roughly 2:1 ratio) for best results
• Skip it if you're a sprinter, have liver issues, or are new to training

Honestly, the research isn't as solid as I'd like—there are still gaps in our understanding of optimal dosing and individual variation. But in my clinical experience with dozens of endurance athletes, when used correctly, MCT oil provides that steady energy source that helps them maintain pace when glycogen starts running low.

Disclaimer: This is general information, not medical advice. Talk to your doctor before starting any new supplement, especially if you have health conditions.