Does a High Fat Diet Help Reduce Lactic Acid Buildup?

When I started eating a low carbohydrate high fat (LCHF) diet, I noticed that my athletic performance started to improve once my body made the transition to burning fat over carbs as its fuel source. I had also started Zone 2 training about two or three weeks after I changed my diet. During the first 10 days or so of switching to LCHF, I was extremely sluggish. Not only was my body moving slowly, so was my brain. The sluggishness subsided and the performance improvement started becoming noticeable within a month. I also noticed that my legs did not get the same burning sensations it did when I ran at the faster paces and that my recovery time was cut down substantially! A few podcasts I heard during that time discussed how others eating LCHF had also seen athletic performance gains and had faster recovery times. This totally intrigued me!


I wanted to understand why this was occurring. After a little searching, I found the figure below that shows the process of how carbs and fat are converted to a muscle energy source (ATP or adenosine triphosphate). The figure, "borrowed" from the Muscular Dystrophy Association, shows that lactate or, as it is often called, lactic acid is not produced when the muscle uses fat as a fuel.

There are fast twitch and slow twitch muscles. Fast twitch muscles are much better at generating short bursts of strength or speed than slow muscles. Slow twitch muscles are more efficient for muscle contractions over a long period of time before they fatigue. 

Zone 2 training uses more slow twitch muscles where the muscle burns both fat and carbohydrates as fuel. More fat is burned; however, the carbohydrates, when burned, produces lactic acid. It is the lactic acid that produces that burning sensation you feel in your legs. Lactate starts to build as your intensity increases since more and more carbohydrates are used as a fuel source. At very high intensities, your body produces more lactic acid than it can remove from the muscles, known as the lactate threshold (LT). The increase in lactic acid is the body's natural defense mechanism to prevent damage to the muscle during extreme exertion. The lactate buildup causes a highly acidic environment that slows down the system of breaking down the glucose to energy. As you know, you cannot go hard or fast for very long! Where as in lower intensities, you feel as if you can go on forever.

But here's something interesting! In the article "Zone 2 Training For Endurance Athletes", Iñigo San Millán stated that by training in Zone 2 the slow twitch muscles also become more efficient at clearing out the lactic acid! So by training in this zone, your body becomes more and more efficient at burning fat and removing lactic acid from the muscle. Therefore, this helps you on both short fast races or training days and longer endurance races or training days.

But did you know that you can also use your diet to help teach your body to become an even  more efficient fat burner? By eating LCHF, your body learns to burn fat all day long, not just during training! For most people, eating a high carbohydrate will not allow the body to burn fat consistently throughout the day due to constant insulin spikes the body experiences each time carbohydrates are consumed.

I wanted to point out that when I switched to LCHF, my top running and cycling speeds initially came down. I also lost my ability to do a quick burst of speed, especially on the run. After a couple of months of both LCHF and Zone 2, my speeds gradually improved and then started to exceed my past abilities. After many months of training (without interval work), I got back that burst of speed I once had. It just took my body a little time to adjust.  This year, I have interval work built into many of my training days and I have no issues doing quick burst of speeds.

So, does a high fat diet help reduce lactate build up? If you work on being an efficient fat burner via your diet and training, it should work based on what I have experienced over the last 17 months.