Fat-Loading for Race Performance (part 1)

sarah cuff Running Performance 15 Comments

I’ve put off writing about fat-loading for some time now because each time I’ve gone to blog on it, the topic felt too large. Instead of continuing to sidestep it, I’ve decided to write about it in 3 parts: first, why you’d want to fat-load; second, the science behind fat-loading; and finally, how to fat-load.

I first learned of “fat-loading” from Matt Fitzgerald’s book The New Rules of Marathon and Half-Marathon Nutrition, a method used to enhance ones running performance in endurance event lasting longer than 2 hours. The purpose of fat-loading is to teach the body to burn its own fatty acids as fuel (to a greater extent than it already does), thereby conserving glycogen stores. Conserving glycogen stores as much as possible will help to prevent ‘bonking’ or ‘hitting the wall’ on race day. Plus, fat-loaders tend to appreciate one of the side effects of fat-loading is a tendency to ‘lean out’ considerably – helping those who struggle to reach their racing weight to achieve it.

With the promise of increasing my fat-burning capacity and a few sound arguments that made nutritional sense to me, I decided to give it a try. Leading up to my Eugene marathon last July I fat-loaded for 10 days and then carb-loaded for 3. My training had not gone to plan, yet I ran a one minute personal record (PR) that race (3:31:15). And that was with my fuelling mishap – meaning I consumed only one half of a single gel the entire marathon (not advised but apparently doable). I also toed the start line considerably leaner and lighter than ever before.

I didn’t walked into this whole fat-loading thing completely blind – I first talked to a number of marathoners who had also personally tried it and experienced great benefits from it.

Katie Hynes is a registered dietician in New York. Like me, she originally heard of fat-loading from Fitzgerald’s book, and in her own words:

“I was intrigued by the idea of increasing fat to increase fat burning capacity and decrease the reliance on carbohydrate (glycogen) as fuel. Focusing on fat rather than extreme low carb made scientific sense. Yes, calories from carbohydrate are automatically lowered as you increase fat intake, but that is not the only goal.”

Katie completed the 10-day fat-load followed by a 3-day carb-load before her 2013 Chicago Marathon. While she didn’t believe her training had been as strong as the year before, she managed to run a one minute PR (2:51:56) and strongly believes that fat loading played an integral role in getting her that PR. Upon implementing the same strategy again this past fall for the New York Marathon, she ran a course PR on a day that presented terrible conditions. 

And here’s a fact about Katie – she is 100% vegan. Whereas Fitzgerald claims that vegans shouldn’t attempt fat-loading “unless they are prepared to live on nothing by avocados, nuts, olives, and nondairy cheese”, with her creativity in the kitchen Katie shows us that vegans can fat-load quite deliciously – and any food repetition that might occur is the same type of monotony that the high-fat meat-eaters may experience.

Chris Napier is a talented sport physiotherapist and marathoner who trains with a group of Canada’s elite distance runners. In preparation for his 2013 Scotiabank Toronto Marathon he fat-loaded, albeit more in the traditional manner of cutting out carbohydrates 3 weeks before race day and finishing with a 3-day carb-load. Unlike Katie, he is not vegan and therefore included the likes of steak, salmon, cheese, full-fat yogurt and protein shakes – whereas Katie ate a lot of green protein smoothies, tofu, lots of hemp hearts, chia, walnuts, almonds, avocado, nutbutters, cashew cheese, olives and lots of veggies with olive and coconut oils.

Despite the differences in food, both Chris and Katie ate approximately 60-70% of thier calories in the form of fat. But unlike Katie or I, Chris had also been having an exceptional training season, and this combined with fat-loading resulted in a phenomenal PR – he took 15 minutes off his marathon time (2:35:35)! Chris would and has once again followed the strategy of fat-loading.

After hearing others stories and trying it out for myself, I had clients interested in giving it a try. Catherine Frank lost 5lbs during her 10-day fat-load in prep for her September 2014 marathon and hit the start line feeling incredibly lean and ready. She then proceeded to take 11 mins off her previous marathon time, crossing with her first sub-4 (3:54:54). We had already worked together to prep her for her spring marathon that year also (where she’d achieved a 5 minute PR, no fat-loading).

Tracy Killion wasn’t sure what to except but was ready to try anything for her Sioux Falls 2014 marathon. In her words:

“Surprisingly, I leaned out. I was eating about 200 calories more per day, but lost 2 pounds and dropped additional body fat.”

She also ran a 3.5 minute PR (4:05:53) at the conclusion of that 10-day fat-load / 3-day carb-load.

Victoria Maidhof was extremely pleased, twice over in fact, when she tried fat-loading and found it not only helped her reach her racing weight but also race faster than she had before, crossing the finish line of her December 2014 half marathon over 3 minutes faster than ever before (1:52). And that was in the half-marathon! Typically I’d be more apt to recommend fat-loading for only the full marathon or longer, however she showed me it may well be beneficial in the half as well. And she wasn’t the only one…

Carmella de los Santos attended the Eat2Run Nutrition for Runners workshop before she ran the October 2104 Vancouver Rock ‘n’ Roll Half Marathon, her very first half. Expecting to finish in about 3 hours, she ended up feeling so good she danced across the finish line in 2:19:07! Attributing her new nutrition plan and experiment with fat-loading to her success, she tried it again last week at the Vancouver First Half half marathon and PR’d by over 5 minutes, bringing home a 2:13:39! Suffice to say fat-loading will be part of her race prep leading up to her first marathon this spring.

I actually also tried fat-loading leading up to my First Half half marathon just last week… Knowing it works for me in the marathon doesn’t necessarily mean it’d do anything for me in the half distance – in fact, there’s really no scientific evidence to show it would. But seeing the success of those who’d already tried, I gave it a go. Having been unable to break 1:40 in the half distance since 2012, I ran a 1:37:36 on Sunday. Now, I was also well trained for it – but I do believe success is always a combination of factors – in this case, training and nutrition came together perfectly.

Next week I’ll look at the science behind fat-loading; and the week after that – how to fat-load. Until then…

To deliciously healthy food and stronger faster running… Cheers,


Sarah Cuff, R.H.N.
Holistic Sports Nutritionist
Founder Eat 2 Run Sports Nutrition
CSNN Sports Nutrition Instructor
Better Bodies Club Nutritionist

Comments 15

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    1. Post

      Yes, indeed it is – I’ll do this before any race that I want to ensure a good performance at! If I’ve got a race that I’m using for training, then I won’t bother – but for goal races, yes certainly.

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