Maybe I’m going soft in my old age. (lol)
Maybe it’s because of my sense of scientific curiosity.
Maybe I’m less stubborn than I thought I was.
Whatever the reason, a few months ago I started to spend some time listening to the Endurance Planet podcast on my drive to work, and their constant conversations about low carb/high fat (LCHF) diets for endurance athletes seeped into my brain. At first, I thought it was stupid – we know carbohydrate is the main fuel source for intense exercise. But the science behind low carb/high fat is really compelling: people have been able to change the metabolism in ways that we never thought possible. A seed was planted.
High fat/low carb background
**Disclaimer: there are a lot of theories about high fat diets, ketogenic diets, etc. I’m just going to talk about what interested me specifically, and not get into a lot of detail. If you want some of that, try here**
The reason that I was so drawn to testing out this eating pattern is because the science is legit. Carbohydrate is a quick-burning fuel, and therefore your body wants to use it for anything that needs fast energy or a lot of energy. The problem is, we don’t store a ton of carb. What we do store a lot of is fat. One gram of carb has less than half the energy of one gram of fat (4cal vs 9), so it’s the most efficient way for our bodies to keep energy on hand for times of need. Running long distance is definitely a time of need.
The thing is, if you constantly feed your body carbohydrate, it uses that first. With increased duration of exercise (especially at lower intensities) fat starts to kick in as a fuel source, but by following a low carb high fat diet you can train your body to tap into fat stores earlier on and to a greater extent. This makes a lot of sense: you’ve got less carb hanging around, so your body wants to save it. Sounds like a biohacking miracle, no? Eat less carb = increase fat utilization, i.e. metabolic efficiency = run longer without needing to rely on gels and sports drinks = less chance of GI distress and blood sugar issues, lower body fat content (from using it as fuel more readily), etc. I was curious.
So, without intentionally doing it, for a period of ~4-5 weeks this summer, I kind of started to edge down the carb intake and steer more towards increasing fats via lots of avocado, coconut, and nuts/nut butter; and decreased my fruit/toast/oats/starchy veg/whole grains. I didn’t eliminate these foods all together, but I kept it pretty low. I ran some mornings without eating beforehand (which I NEVER do) and was surprised that it actually felt ok. I had a LOT of veggie egg scrambles. I felt tired, but it was summertime in Texas and I was running in the mid 40s for mileage through the whole thing which is a good amount for me – of course I couldn’t run fast!
Then, I had my annual physical.
I was shocked to see the results:
Total Cholesterol 211 (should be less than 200)
HDL 59 (should be greater than 60)
LDL 141 (should be less than 100)
Triglycerides 55 (should be less than 150)
How was this even possible?! I am a dietitian, for crying out loud! I teach people how to keep these numbers in check every single day. I eat vegetables like they’re going out of style. I exercise all the freakin’ time! I felt like a failure, like I was living a lie. I know it sounds stupid and dramatic but I was really ashamed of these results, and though I told myself it may be related to my recent experiment with LCHF, I also kind of thought that was just me trying to feel better. Perhaps I wasn’t actually as healthy as I thought I was. Perhaps my now-and-then indulgence in a bike ride for a slice of cake at my favorite neighborhood bakery were too much for my body to handle. I asked my doctor to order a recheck of the labs, just to be sure, and though she seemed incredulous about it, she obliged.
Over the intervening 6 weeks, I went back to my normal eating. There was more PB banana toast, more fruit as a snack, more whole grains with dinner. I have to say, I felt better – carbs truly are what your body wants to run on (as in the exercise, but also just in the sense of functioning) and I was less fatigued. When I did try to run hard, it came more easily despite the fact that I was drowning in my own sweat. And that’s an important point – when the weather conditions are hot and humid, you expend more energy while exercising and a greater percentage of that energy comes from carbohydrate. Reducing that fuel during such an extreme time of year was not a good call!
When I went back and got re-tested, I was able to breathe a sigh of relief:
Total Cholesterol 169 (should be less than 200 – a 41-point drop)
HDL 67 (should be greater than 60 – an 8-point increase)
LDL 92 (should be less than 100 – a 49-point drop)
Triglycerides 50 (should be less than 150 – a 5-point drop)
These are big changes in just a month and a half! Clearly, more carbohydrate was much better for my body than more fat. That’s not to say that fat is the enemy by any means, just that carbohydrate isn’t always. Do I think my original high numbers were a direct result of the way I had been eating for several weeks? Yeah, I definitely do. Was it a perfectly controlled experiment? No, so I can’t say for certain, but I am pretty sure the reason my original numbers were so shockingly high for me is because I was eating more of the foods we know to be detrimental for cholesterol and less of the things we know to be helpful. But, because of the way science works, I can’t say that it was causative. I can still believe it though.
So why did a higher-carb diet work well for my cholesterol?
- MORE FIBER: Soluble fiber can decrease cholesterol. Anyone who has ever looked at a box of cheerios or oatmeal can tell you that. The thing is, the foods that contain soluble fiber – fruits, vegetabales, whole grains – are a lot of the ones I had decreased. More of these foods increased the fiber content of my diet, even though I had never faltered in being a nonstarchy vegetable super eater during my little experiment.
- Less saturated fat: Saturated fat comes from animal products and tropical oils, aka palm and coconut. That’s right: coconut oil is a saturated fat and can raise your cholesterol. We don’t have a ton of science on the long term effects of coconut oil on cholesterol because until recently people weren’t eating the stuff as if it was the elixir of life, but I can tell you that the fatty acid content of coconut oil is mostly saturated, and saturated fat has negative effects on cholesterol levels. So, I had more from coconut, and on top of that because I decreased starches that also left more room in my diet to increase saturated fat from increased quantities of animal proteins.
I had to stop listening to that podcast for a while to make sure I didn’t creep back down with my carbs. To my surprise, when I came back to it more recently the prevailing viewpoint had become more moderate when it comes to carbohydrate restriction. In fact, there has been a lot more discussion about how carbs are actually really important for women and hormonal health! The host, Tawnee Prazak Gibson (who combines “cool chick to shoot the shit with” and “sports nutrition supernerd” into the perfect blend, IMO) talks a little about the more moderate approach she has been taking here.
I’m still fascinated to see how the science on this stuff develops, but having been there and seen what it has done to my body and how I feel, I know that I do way better on a higher-carb diet. If that means that I have to carry some gels with me while on longer runs and when training at higher intensity in the summer, so be it. I’m cool with that!