nutrition · running

endurance sports and low carb/ketogenic diets

I almost don’t want to mention this for fear or “jinxing”, but my running has been feeling good lately. Even in the almost constant gross heat and humidity, the miles have flowed a lot better than they have in a while. I don’t think it’s real rocket science as to why – I’ve been taking it easier, running with no pressure, resting a bit more and doing other things like yoga, barre and nothing. I liken this to taking a running “chill pill” and I think it’s sort of working.

because I was feeling all the feels about running this past weekend, I decided to go on a longer run down the West Side Highway and Hudson River Park. I love running down there, but usually only do so when marathon training because it’s an out and back run and takes a long time. The solution? Take my metro card and subway back home when I felt like it and was near a subway. I’ve actually never done that before because I don’t really like being soaked with sweat far away from home and always end up getting cold. But! YOLO, right? So I headed out for what I thought would be 10 or so miles without any fluids (there are tons of fountains) or nutrition (usually don’t use this for runs under 12-13 miles).

happy place. but from the winter/spring of 2016 as I usually don’t like taking my phone out mid-run

it was such a beautiful morning and I loved being out there without any sort of pacing plan or route. After about 8 or 9 miles my energy started getting a bit low, which is pretty normal for me these days since I take Peanut for a walk before my runs now and haven’t really nailed a new pre-run fueling plan. My usual half a banana doesn’t really cut it so much anymore. So, ok. Low energy, no fuel, but I had a credit card and an idea of where I could get the subway and a snack. The only thing is that it was a bit far away – I was downtown near Battery Park and the WTC and I wanted to be in Union Square. Those three or so miles uptown were tough, and as I neared my destination my legs felt more and more like heavy bricks. I felt so depleted, and I probably used my last glycogen store as I triumphantly pulled up to the Juice Generation on 18th street. All I could think about was slurping down something cold and sweet, and decided on an acai bowl because I’ve been wanting to try one for a while.

hit the spot in a major way.

and all this got me thinking of another nutrition trend I just can’t get down with, and that is endurance athletes going on “ketogenic” diets. One principle of the diet is basically running on the depleted state that I unintentionally ended my run on Sunday. It’s miserable. And I’d hate for anyone to purposefully do that to themselves under the false belief that it’s going to help them get that PR.

what exactly is a ketogenic diet?
these are diets very low in carbohydrate, low in protein and very high in fat, with the goal of putting the body into ketosis. This is when there is a build-up of acids called ketones in the body, as a result of burning fat stores in the absence of glucose. A true ketogenic diet is something like 5 percent carbohydrate, which is very hard to do unless you’re eating butter and cheese all day and have some direction from a dietitian. In fact, most athletes who say they are on a ketogenic diet are often just on a low carbohydrate, high fat diet because they are consuming too many carbohydrates to achieve ketosis. That said, though, they are still consuming far too little carbohydrates to fuel their activity!

so what is the point?
there has been some recent hype touting performance enhancements achieved by drastically cutting carbohydrates and increasing fats, with the idea being the body will burn more fat as fuel. We don’t necessarily need to achieve ketosis to do this. The body has limitless stores of fat and very limited stores of glycogen, so this is thought to be a much more efficient fuel source and one that can help us go longer, faster. It sounds good on paper, at least.

but that’s really all it is, and it’s not for lack of research. If an individual begins consuming a low carbohydrate, high fat diet, the body will physiologically adapt by increasing fat oxidation and reducing carbohydrate utilization. But while our capacity to use fat for energy enhances when we have consistently limited carbohydrate stores, this does not translate to a better performance in endurance events. There is a lot of recent research to back this up. If we train our body to use a less-preferred source of fuel (fat), it will also do so during an endurance event like a marathon. The problem is that all it really wants is carbohydrates, which it has adapted to use less of. Even if you carbohydrate load in the few days before said event, the body remains less efficient at using glycogen stores once it adapts to using more fat.

one of my fave carbohydrate forms – toast!

more research
this study is the most recent and thorough I’ve read, and I had the pleasure of listening to one of the study investigators – Dr. Hawley – speak at FNCE last year. He talked about the study a bit (it had yet to be published) and gave such compelling evidence as to how and why low carbohydrate, high fat and/or ketogenic diets just don’t work for endurance athletes. His study used elite race walkers who were all put on the same intense training program, but one group followed a low carbohydrate, high fat diet, another a high carbohydrate diet and another a periodized carbohydrate diet (still high in carb, just spread out differently during the day). At the end of the training program, all athletes had improved aerobic capacity, but only the high carb and periodized groups experienced an improvement in race performance (a timed 10K). This is because, as I mentioned above, when we adapt to a high fat diet by increasing fat oxidation, we also adapt by using less carbohydrates and reduce carbohydrate oxidation. It’s this adaptation that limits performance capacity.

another important point is that our brain and central nervous system also depend on glucose (what carbohydrates are broken down into) to function. And if we are in a state of depletion, we also may not be thinking clearly. This can effect things like pacing, perceived effort and even simple decision making during a race. Not really a recipe for success, right?

in conclusion…
still, the anecdotal evidence persists and with the help of social media, one or two “success” stories can and has snowballed into a real trend. I don’t think this one will last forever, though, with science firmly rooted against it. And because even anecdotally, if you look at the plates of most top endurance athletes, they are more often than not generous on the carbohydrate front. And that is for good reason.

 

 

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