Coach, should I be on a 'Keto' diet?

Alan Couzens, MS (Sports Science)

March 30th, 2015

Above: Me and my favorite 'fat-adapted athlete', Kona

It’s that time of year again, we’re on our way towards beach season and that means the same thing for athletes as it does for everyone else. Folks start looking around for the latest, greatest diet plan “guaranteed” to get them that elusive 6 pack (and for athletes - notch their fat oxidation up a few grams/min in the process). For the last couple of seasons that ‘magic bullet’ has been a ketogenic diet.

First, a quick review of what constitutes a ketogenic diet: Ketosis occurs when carbohydrate availability is so low that the body has to come up with a “plan B” for fueling processes which typically run on glucose. The most significant of which is the brain! The plan B that it comes up with is the generation of ketone bodies as a byproduct of fat & protein metabolism. The ‘fat-adapted’ brain can generate sufficient energy from these ketone bodies to keep the wheels turning over. An important side note - while ketosis almost always signifies a high level of fat oxidation (at least at rest & low intensity exercise), a high level of fat oxidation can absolutely occur without going to the extremes of ketosis. I talk more about that here.

All good so far… very high levels of fat oxidation (good for athletes), a brain that continues to function – another positive. So what are the negatives of this state?

The pic above is of my dog Kona, a ‘fat adapted athlete’ :-) Kona has been on a high fat diet for an extended period of time. Last week she had some crystals in her urine and her Vet recommended the inclusion of a (high CHO) prescription diet to ‘flush out’ the crystals. Despite a very gradual introduction to the new food, immediately following this shift, my wife and I spent the better part of a morning cleaning up dog puke! This is not the first time that I’ve seen this connection. I’ve seen exactly the same thing in non-furry’s who have been on a ketogenic ‘Atkins style’ diet for an extended period of time and then (usually for athletic reasons) reintroduce some carbohydrate into their diet. So what gives?

The phenomena that leads to this reaction has a scientific name – peripheral insulin resistance. “Isn’t insulin resistance what I’m trying to avoid with this diet?” I hear you say. Indeed, a high carbohydrate diet in the absence of large amounts of exercise results in a futile cycle of insulin being released in response to high blood glucose as a messenger for energy stores to ‘open up’ and let in some of the available energy. If energy stores are full, they send back the message “Sorry pancreas, parking lot full here” and eventually after a while, they just get sick and tired of the insulin messenger continuing to show up so they become literally resistant to this messenger.

However, this can also occur in another situation…

The brain’s preferential fuel is glucose. It can function on a “back up generator” of ketones to a large extent, however, the body is geared towards ensuring that any glucose that hits the blood stream, first and foremost gets routed to the brain. A part of this ‘routing process’ is to make sure that the ‘gates’ to the muscle and fat cells remain closed until the brain gets its share of glucose, i.e. that the cells do not respond to the insulin messenger until the brain is taken care of. This protective mechanism is termed peripheral insulin resistance and it has consequences when enacted over long periods of time…

Studies have shown a significantly blunted insulin response in folks who are ‘out of practice’ in properly dealing with blood glucose. The following chart from a study titled "Insulin Sensitivity And Glucose Tolerance Are Altered By Maintenance On A Ketogenic Diet" (Kinzig et al., 2010) looked at difference in blood glucose response in ‘fat adapted’ (Ketogenic Diet) rats vs rats fed regular chow.

You can see that in the fat adapted condition, after CHO was given, blood glucose stayed significantly higher for longer than in the regular rats. The fat adapted rats, while still having a structurally healthy pancreas, were ‘out of practice’ in what to do with sugar when it hit their blood stream. Though for different reasons, their glucose intolerance was similarly poor to the other extreme of a diabetic rat (!) and this glucose intolerance has predictable non-functional defense mechanisms to get rid of the glucose, one of which is nausea and yadda, yadda, yadda, your dog throws up all over the living room :-)

However, your dog throwing up over your living room may not be the worst of it….

Many of the negative health consequences of prolonged insulin resistance are directly due to unabated high levels of sugar in the blood. Current thought is that many of the inflammatory problems that are associated with a high sugar diet are directly associated with the mechanical stress of sugar particle crashing into and ‘buffing up’ the walls of your circulatory system. It doesn’t matter so much why you have a lot of sugar particles in your bloodstream – because you’re out of practice dealing with them, because you don’t have any room to get rid them or because you are just eating too darn much of it. Either way, the consequences are the same…

This presents a particular problem for athletes because the option of just saying good bye to sugar forever just isn’t there, not for the serious ones at least. One of the key energy systems for almost every athletic event (all the way up to seriously competitive Ironman) – glycolysis, demands glucose. Therefore, for all serious athletes, in addition to the health reasons mentioned above, from a performance perspective, having a system trained in what to do with glucose (other than throw it up or pee it out, i.e. actually use it for energy) is important.

An additional consideration for athletes - Insulin is a powerful anabolic messenger that tells the athlete’s system to go into ‘growth mode’. It is such a powerful messenger that athletes with less than impeccable ethics, even use it as a performance enhancing drug(!) Think about it – more insulin = more powerful signal to the muscles to take up all of the good stuff floating through the circulatory system – both glucose – which is then stored as glycogen - and amino acids which become the building blocks for stronger, faster, more athletic muscles. In the absence of insulin, growth is retarded. This extends beyond theory – I’ve seen it in keto athletes that I’ve coached. Their response to training is, on the whole, not great.

The above points gel with my real world experience as a coach. Based on the keto athletes I've worked with to date. I've seen…

Which brings me to the following conclusion...

Providing your body knows what to do with it, a little bit of glucose (and the insulin it brings with it) is great stuff!

And that’s what this question on the merits of a ketogenic diet all comes down to – does your body know what to do with glucose?

One of the sharpest double-edged swords of modern times is that sports and health sciences are colliding. This has way more positive than negative implications but it does have the problem that athletes on the whole (at least the type that are reading this blog) are NOT representative of the general population, at least from a health (and probably from a psychological :-) perspective.

In the general population, metabolic syndrome and insulin resistance is absolutely epidemic. Frankly, as a percentage, there are not a lot of folks left in the Western World with a healthy metabolic system. But…

Those that are left are likely to be those who challenge that metabolic system on a regular basis, i.e. us!

This is where the health/performance thing gets tricky. Tim Noakes is shouting from the roof tops that insulin resistance is a global problem. I agree with him. The problem is, because he was a relatively serious athlete & comes from a sporting background and because he is IR, he is making the giant leap that most athletes are also IR. Based on my observations to date, at least in healthy Ironman athletes, this is not the case.

So, how do we determine if we are insulin resistant and in need of a ketogenic diet?

How do we determine if our metabolic system is healthy enough to handle an appropriate amount of CHO?

We test!

In my next post, I’ll talk you through a simple test (that I’ve taken a number of my ‘keto-curious’ athletes through) to assess your own metabolic health and the consequent applicability (or lack thereof) of a ketogenic diet FOR YOU.

For those with seriously damaged metabolic systems (i.e. diabetics), the option of ‘re-training’ the system may be long gone. In these cases, a ketogenic approach has a lot of merit. However, it’s my firm belief, that in the absence of a true need for a ketogenic approach, serious athletes who go down this route may be doing more harm than good & that such an approach may even promote the very insulin resistance that they are seeking to avoid!

If in doubt, follow the lead of the Buddha - over the long run, the middle way usually works out to be the most prudent option :-)

Eat smart,




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