In my last post I discussed some of the potential health benefits of reducing intake of refined carbohydrates, and increasing the proportion of dietary fats. This is a topic which is very much in vogue right now, and I believe the science will ultimately prove that for many of us, this is a good approach to healthy living and longevity. But hell, this is a running and training blog, so how do we apply some of these principles to training and racing.

An approach that I have been using for some time now, is known as Optimised Fat Metabolism or OFM. OFM is an approach developed by Peter Defty at VESPA. A lot more information is available at . It’s an approach to dietary periodisation, much like we periodise our training schedules. Essentially, the OFM approach dictates that we specifically maximise our ability to utilise fat as fuel, and that we time our intake of carbohydrates (CHO) to improve our ability to train and race hard.  

The vast majority of ultra endurance athletes spend most of their training miles at the easier end of the intensity spectrum. As we have discussed in the previous post, these efforts are almost entirely aerobic efforts, and by eating in a HFLC fashion, we can become very efficient at utilising fat as our main energy source. The single best way to improve our ability to metabolise and mobilise our stored fat stores is to limit dietary CHO consumption; and remember that even the leanest athlete with only 5% body fat, stores around 30,000 kcals of energy in adipose tissues. So long as we minimise our dietary CHO intake,and train aerobically, we can become very efficient fat adapted machines, and our training sessions will be fuelled by our stored fat; and we have almost limitless supplies. This means that we need to consume less calories during our runs, and anecdotally most of us who follow this dietary approach find that we are less hungry, and can survive on less during the day. Cravings for food seem to dissipate, as we are carrying more than enough calories in our fat stores to keep the fire well stoked.

So practically, how does this look?

For me, my approach to training, especially at this time of year, is to keep the intensity relatively low, most of the time. I won’t divulge all of my secrets, as there is some competition out there (!), but for these lower intensity training blocks, fat is absolutely the preferred fuel. This means I eat a very low CHO diet (for me this is around 50-75g per day). Now what exactly defines a low carb diet is certainly open to some debate, and for some that may mean 100-150g daily, for others 50g, or even less. Nutritional ketosis, which I won't go into here, is probably what most people use to define low carb, and depending on whether you are very active, and whether you have other health problems, the numbers can vary quite a lot. For most people however, especially those reading this blog, 50g or less will likely get you there.


Breakfast is a fatty meal - eggs, avocados, and cheese are common ingredients. Coffee with cream, and maybe blended with butter/coconut oil is always on the breakfast menu. Lunch may consist of a few nuts, leftovers from the night before, chicken, salami, salads, or low CHO fruits - the best options seem to be blueberries, strawberries and blackberries in moderation. Dinner is typically meat or fish based with a large salad or sauteed vegetables. I don’t shy away from butter as my family will attest to, so vegetables will usually be doused in it! They will also attest to my love of cheap meat cuts like liver and kidneys, which doesn’t go down too well, so I’m usually on my own when this is on the menu! I tend to snack on cheese, pate, nuts, almond butter, low CHO fruits and avocado. I drink water and coffee during the day. A glass of red wine in the evening is only 5g of CHO, and a block or two of good quality dark chocolate does not add significantly to the CHO load! There are lots of other options, and in general I find that this diet is for the most part very palatable, and even indulgent! I log my intake every few days, to ensure there is no carb sneak. The MyFitnessPal app on the iPhone seems to be the best tool for this. If I’m on top of things I’ll get about 75% of my daily calories form fat sources. I've posted a couple of screen shots below.


So what about the high intensity days? Well OFM principles suggest that CHO timing is a crucial component. Extra CHO can be consumed the evening before a race or particularly hard training session. I think common sense dictates that the extra CHO should be in the form of low glycemic index CHO to minimise insulin spikes. Most of the LCHF athletes don’t overdo it however, and from the few I have spoken with, it seems that most will increase their intakes only into the 100-150g range, which would still keep them very much squarely at the low carb end of things. Immediately after a hard training session, I think this is a good time to replenish some of the depleted CHO stores, so again this may be when I’ll grab some extra carbs, in the first 15-20 minutes after I’m done. For me, howeve, as an ultra runner, I don’t do a lot of high intensity training, so I don’t always need to do this. During prolonged activity, despite being well fat adapted, some CHO is necessary. We are always tapping into our  glycogen stores to some extent, and OFM recommends a slow steady trickle of CHO. For me this is usually in the form of an occasional gel, but I know that many will prefer the more slow release complex carb approach, such as that offered by Generation Ucan products

Another commonly used approach is to go ultra low carb at the end of a heavy training block. So if I have 4 or 5 days of harder training, big volume, lots of miles etc, then in the week after, when I am in full recovery mode, a really low CHO intake lends itself well to recovery. I feel that I am less sore, and joints and muscles feel less inflamed. But the OFM approach is quite individual, so if you want to jump in, you need to be open to try a few different things.

By limiting CHO consumption to higher intensity days, to racing and to the immediate recovery period, fat adapted athletes seem to maximise their response to ingested carbs, much like those who don’t consume caffeine seem to respond more dramatically to it’s effects when they do ingest it!

The other part of OFM is of course VESPA. . This is the product developed by Peter Defty and his team. VESPA is a supplement designed to improve access to our fat stores - they call it a ‘fat burning catalyst’, and whilst there are many skeptics out there, I’d suggest you give it a go. I first noticed the ads in the back of ultrarunning magazine and was intrigued. After trying it, I am a convert, and a believer, and yes - I am an N=1 example, but as I’ve previously  stated, I’m all about maximising my own performance to give me an edge! I purchase the product (I’m not sponsored, though Peter Defty has given me a lot of advice) as do many other ultra athletes, and have found the results to be pretty dramatic in terms of how I feel when I’m out there. Part of this of course is being well fat adapted and trained, but I certainly seem to notice the effects when I don’t use it. And whilst it isn’t cheap, I find I consume way less gels when I use it, so I believe there’s an ultimate savings to be had! I love the Ultra Concentrate packs, as they are so tiny you don’t notice you’re carrying them. For me, I try to consume 1 pack about 45 mins before a long run, and I take a single pack every 2-3 hours. This approach seems to work well for me, and I haven’t had any GI distress associated with it’s use. The taste is pretty strong, so I suggest a few gulps of water with it, and some folks mix it in their bottle. I know that a lot of other elite ultra runners are using it too - folks like Zach Bitter, Paul Terranova, Jon Olson and Nikki Kimball are advocates. Whether you choose to try VESPA and OFM is of course personal, but so many of use use our Gus, our sports and recovery drinks all the time, and they aren't cheap either. We all have our favorite brands, so I suggest you consider giving it a go. And no, there is no benefit to me in promoting this!


So what’s new with Fat Adapted athletes? What is on the horizon?

Well this is where things are about to get interesting, especially when the results of the FASTER (FASTER=Fat-Adapted-Substrate oxidation in-Trained-Elite-Runners) study are published. This seems to be a well designed trial carried out by Jeff Volek et al. What this study will show conclusively, and there are some preliminary results available, is that fat adapted athletes who follow a LCHF diet are able to exercise at intensities much higher that previously thought, whilst utilising large proportions of stored fats. In fact it seems that the fat-adapted athlete can tap into stored fat stores at almost double the rate of a conventional ‘high carb athlete’. It was previously thought that the maximal rate of fat metabolism in a well trained athlete was around 1g/minute, and that most athletes were around 0.45 - 0.75 g/minute. In the FASTER study, in the habitual LCHF athlete cohort, the lowest rate of fat metabolism during exercise was in fact 1.1 g/minute, and the highest rate was 1.8 g/minute, almost double what was previously though possible. Maximal rates of fat metabolism in fat adapted athletes seems to peak at around 75% of VO2max, and even at higher intensities of exercise, the fat adapted athlete was able to utilise fat much more readily that his high carb counterpart. Muscle biopsies were also part of the study protocol - these must have been some masochists - I haven't seen preliminary data, but it will be very interesting to see the muscle biopsy data.

The final study is not yet published, but will surely make for very interesting reading and commentary. Personally I think it could well be a game changer, especially in the endurance sport world, but whether this will be enough to change the minds of sports dieticians and coaches remains to be seen; many athletes, however,  seem to be way ahead of the curve, and are posting world beating results by following this approach. And if I have to wait 10 years for the science to prove this definitively, well, I'll likely be past it!

I hope this is thought provoking. Feel free to send any thoughts/comments.

Tim Olsen