Low-Carb/High-fat eating. What is it and who is it for?

There are a confusingly huge amount of labels out there that describe different variations of a Low-Carb diet: Paleo, Atkins, Ketogenic, & Optimized Fat Metabolism (OFM) all describe a low-carb plan.  I don’t know enough about the specific nuances of any of them to sort out which is which so I will just describe how I eat and you can call it whatever you like.

I get the majority (75% or more) of my daily calories from high-quality fat.  I try to eat around 100-120g of protein a day, which accounts for roughly 15% of calories.  The remaining 10% come from carbs.   Depending on how many calories I burn in a particular day, the total grams of carbs typically ranges from 30-75.  Please note that this is NOT a high protein plan – the main calorie source is FAT.

I have been eating this way since October of 2012 and it hasn’t been hard to stay the course. 

Why do I do this?  - There are a few reasons...
1. It is an effective way to lose or maintain weight without much discipline.
I weighed 140 pounds in June of 2012 and had just finished the Kettle 100, at the time it was my 5th 100 miler since 2009 (I say this just to reflect that I wasn’t sedentary).   I decided to tighten up my diet and drop gluten and sugar.   That SUCKED!   I really had to be disciplined and I CRAVED sugar!  I did manage to shed 3 pounds, but I really had to work at it.   In October of 2012 I went all in on the Low-Carb/High-Fat plan (Thank you Zach Bitter!) and have been on it ever since.  The food is satisfying, I don’t need to count calories, and I dropped down under 129 pounds.   I recently had my body-fat tested using a Dexa scan at the University of Connecticut and it showed 6.7% - Lean!
2.    It helps promote better recovery from running – I feel better more quickly and I can handle more miles and more intensity.
There is a lot of science that indicates that carb ingestion creates inflammation – not only in the heart, but all over the body.  Stands to reason that any inflammation beyond the damage of running miles just adds to the load your body is already dealing with.  
3.     Runners that are fat-adapted need to take in little or no calories when running below lactate threshold (65% of Max VO2)
A runner that is fat-adapted utilizes body fat for energy instead of relying heavily on muscle glycogen when using aerobic metabolism (More about this here).  THIS IS ONLY WHEN RUNNING AEROBICALLY!  When you run hard (think just about every race where you are breathing hard) your body will start burning carbs.   The harder you run, the more carbs you burn.   For a 100 miler, however, the pace is slow enough that if you are careful, you are likely metabolizing energy aerobically most of the time.  The implication here is that the amount of calories needed to ingest to complete the race for a fat-adapted runner is less, since their body will rely more on stored body fat instead of burning through limited muscle glycogen stores.  Any plan that allows me to eat less gels and goos gets a thumbs up for me! 

Based on just these three reasons, I would say that a lot of runners could benefit from exploring a Low-Carb/High-Fat eating plan.  No matter what race is your specialty, everyone will be faster when body-fat is minimized and can work-out harder and longer with reduced recovery time.   The benefit of eating less during a race is probably only going to apply to ultra-marathoners though.  The longer the race and the slower the pace, the more this benefit comes into play.   Limitations for elite athletes that train and race at high-intensity will temper the benefits for racing. 

This all being said, Low-Carb/High-Fat is not the only plan you can have success with – Obviously there are TONS of athletes thriving on traditional diets that are High-Carb/Low-Fat and it is not my goal to discredit or discourage anyone from eating this way either.  Read a lot, ask questions, and find what works for you.


  1. Any estimates available for VO2 Max for us hobby joggers? I think I could probably estimate 65% of Max. Any graphs you know which show race times and the correlation between the 2?

  2. Without the equipment, it would be hard to predict VO2 max. Any "general" calculators are not likely accurate, and even if they were, how would you know you were at 65% of MaxVO2 without the fancy equipment? A more practical way to go about it would be to look at determining Lactate threshold by heart-rate. Lots of info and cheap equipment to do it from.

  3. It seems counter-intuitive to eat fat to lose fat, but then most people believe that you need to eat protein to gain muscle (try telling that to a 2000 pound steer who eats grass). All I have been reading about lately is "Inflammation", both in athletic recovery and in heart disease. Much of this seems related to processed foods (read:wheat carbs, sugar carbs). It's starting to make sense. Nutritional science is in the 1800's compared to medical science. One thing I am careful about is "compartmentalization". A carb is not a carb, vitamins are not vitamins, I think the source and structure play a part. In my own experimentation, 100 grams of sugar carbs vs. 100 grams of carbs in an apple vs.100 grams of wheat carbs do not react the same way. The wheat and the sugar definitely make recovery the next day harder; the body has to break them down to use them, stressing the pancreas and liver. Raw fruits and vegetables contain enzymes necessary for their digestion. For example, a raw apple theoretically contains the enzymes necessary for our bodies to utilize its nutrients; this goes away once heat is added to change the form of the apple; apple juice, apple pie for example. So once you are past the point of adoption, how much fruit can you eat? I get the vegetable part, but I would really miss my fruit.

    Thanks Brother Grub! Good stuff!

  4. Great points Mar-T! You are right that all carbs are not equal. Vegetables are a great example of a carb food source to load up on since you get a ton of nutrition for very little carb ingestion. The fiber in vegetables and some fruit (berries especially) buffer an insulin response and are great to include in a low-carb/high-fat plan. I personally eat very little fruit only because any vitamin or mineral you can get from fruit, you can get from vegetables or meat without the higher sugar content. It's a personal choice though, and I wouldn't shy away from fruit if thats a make or break thing for you. Early on though, I would keep fruit to minimum since 50g of carbs doesn't go far.