LCHF and IF for the female endurance athlete (IMHO).

Following on from the couple of blogs I wrote about Dan’s LCHF athlete lifestyle, I got a lot of messages from women regarding my opinion of it for the female endurance athlete. Great question, especially as – if you look at social media – there are nutritionists who warn against the danger of LCHF (and intermittent fasting) for women, to the point that the blanket statement is that it is harmful and not to be undertaken. Whilst it is hard to be objective in the nutrition space – all of us influenced to some degree by our own experiences – the low carbohydrate and fasting space seems to bring with it its own special degree of hysteria. The prevailing message is that both low carbohydrate diets and fasting is too stressful on the endocrine system of females (which regulates hormones) and causes a reduction in metabolism and reproductive potential. Thus, it is to be avoided at all costs. This point of view may be drawn from clinical experience of the practitioner and be dependent on the type of client they see. If their target audience are women who have struggled with maintaining a healthy weight and have problems with eating enough, then the opinion of the practitioner could well be influenced by this (and is entirely sensible!) Likewise, I see many women who’s hormones benefit from periods of intermittent fasting while utilising a LCHF protocol. What we see in clinic will dictate our points of view, regardless of how objective we try to be.

I have in the past written about the negative impact of fasting and calorie restriction on the expression of genes that regulate kisspeptin in the body, a hormone involved in our reproductive cycle. However I will point out that the effects seen in studies conducted in rodents may be more dramatic than if they were carried out as clinical trials in humans. Rodents have a much faster metabolism, thus a 24h fast for a mouse is equivalent to a 3 day fast in humans. Likewise, chronic caloric restriction over a week, where the mice lose close to a quarter of their body weight (and which is thought to be responsible for the downregulation of the kisspeptin receptors that result in negative effects) may be equivalent to 12 or more weeks. Rodent models in science are great for illustrating potential mechanisms, but can never be viewed as hard data as it pertains to humans.

Alongside any scientific data that exists, I think it’s important to step back and consider perspective here. What we should all be aware of is that there is no one right dietary approach for everyone, and often there is no one dietary approach to suit someone for the rest of their lives. As things change, so do our nutritional requirements. Low carbohydrate diet and intermittent fasting is not exempt from this – therefore to say that it is not suitable for any woman is, quite frankly, erroneous and misrepresents what we see in the literature and what we see clinically. While certainly a vast majority of the studies investigating lower carbohydrate diets have been conducted in males, there are studies showing a positive impact for overweight women with infertility. Further, it is accepted best practice to include periods of low glycogen availability in the training schedules of athletes. Even in the researchers who err on the side of pro-carbohydrate diets recommend cycling carbohydrate intake to be sometimes low, and sometimes high, to upregulate fat oxidation pathways that allow the athlete to become more efficient at burning fat. To state that no female athlete should start an exercise session in a fasted state goes against current best practice for endurance performance.

Possibly the negative impacts of fasting and low carbohdyrate diets are not about the fasting period or the carbohydrate content – it’s much more likely to represent chronic underfuelling – i.e. a lack of calories over an extended period of time, with no thought given to cycling of both energy intake and/or macronutrients. It’s just low, full stop. That’s why it is important to work with an experienced sports nutrition practitioner (like me, Kaytee Boyd, Caryn Zinn as some top picks) to ensure these training tactics are used to the advantage of the athlete in a training cycle, not to the detriment of them.

Don’t misread this as a recommendation to do all sessions in a fasted state, to undergo an intermittent fasting protocol that involves skipping breakfast every day of the week, or that everyone should adhere to a very low carbohydrate approach. If you’ve read any of my information (or followed anything I’ve suggested) then you’ll know this isn’t the case. The point of this blog is to remember that there is no one right dietary approach for everyone, and that if you’re successfully adhering to a lower carbohydrate diet with periods of intermittent fasting and feel it’s working well for you (ie no sleep, hormone, training or recovery problems), don’t be concerned with the rhetoric that exists regarding the harmful nature of this. You are your own best investigator when it comes to your nutrition, and your experience is the most important data when it comes to you.

Intermittent fasting

Post on IF, cue picture of empty plate with clock. #standard (PC http://www.stack.com)

The Plews on racing LCHF

Last week I detailed Kona Ironman age-group champion Dan Plews’ daily and training nutrition using a LCHF approach. How does this change in the lead up to an event, and what does he do on race day?

Like conventional sports nutrition principles, there is somewhat of a carbohydrate loading phase pre-race. This isn’t the 500-600g of carbohydrate that is recommended for most athletes in the three days before (which generally leaves an athlete feeling lethargic and bloated), however it is more than he would generally eat. Don’t forget that tapering for a race is, in effect, carbo loading, as the muscle glycogen stores are not depleted during training and it allows them the chance to be replenished and not in the deficit they normally are. Based on Rowlands paper which showed that a higher fat diet with a preload of carbohydrates, he’s dialled in his approach that Dan now feels works really well for him. He lifts his carbohydrate intake from the 80-100g he typically eats in the days prior. On the Wednesday (for a Saturday race), he will include additional potato or sweet potato in his evening meal, taking him to ~125g carbs per day. This increases to ~175g per day on Thursday and Friday (the two days before the race) – including fruit alongside the potato or sweet potato. In addition, he makes sure snacks etc on hand are low carbohydrate so  not to be caught out during the lead up period with having to rely on the petrol station or four square options. If you do have to rely on these, and are looking for lower carbohydrate, then biltong, cheese snacks, even lower carbohydrate protein bars can be good stop gaps. On race morning before Dan’s Kona race he opted for was porridge: oats with a bit of Super Starch added, which is a slow release carbohydrate to not inhibit fat burning, and is a higher molecular weight carbohydrate, so it is easier to digest.

During the race:

Despite research studies in this area using a ‘train low glycogen, race low glycogen’ model to determine the efficacy of a LCHF approach for sports performance, in practice Dan follows what practitioners advocate: a ‘train low, race high’ model. Ideally, the train low approach has enabled you to increase your efficiency to burn fat as a fuel source in addition to using carbohydrate that you have stored or take on board, thus maximising the amount of fuel you have available. Dan takes in around 50g carbohydrate per hour;  because he is very efficient at burning fat, he doesn’t need as much carbohydrate as he would otherwise. A real benefit of this is that it minimises the likelihood of gut issues many endurance athletes experience during a long event – the more carbohydrate fuel you have to take on board, the more opportunity there is to get the dose wrong. Importantly though, the more fatigued you become, the more your body will divert blood supply away from the gut to the muscles, and thus impacting on your ability to digest the fuel.  During Kona Dan used energy blocks with gels on the bike, and a couple of gels with some swigs of sports drink or coke during the run. His paper Different Horses on the Same Courses outlines how to take this individualistic approach to fuelling, as will his online course that you can sign up to by clicking here.

Finally, post-race, Dan gets back on board the LCHF approach fairly swiftly, as he has seen the impact that a higher carbohydrate fuelling day has on his blood glucose level across the course of the following week. It certainly doesn’t reduce down to normal levels the day after, and it’s likely that inflammation and muscle damage impacts on this too. Your best bet is to (as soon as possible) get back to your LCHF diet and help your recovery process.

LCHF for the top end:

Whilst LCHF is increasingly more accepted in the endurance space as part of the approach, what about at that top end – does it limit performance there? There is very little quality research on this, however Dan’s research group found that there was no detriment to perform high intensity intervals (as I blogged about here), but the jury is definitely out on this point and I wonder if, like many things, it is individual. A person’s ability to metabolise fat as a fuel source and use it at a higher intensity is trainable for sure (that’s what fat adaptation is all about), but there could be individuals who are less able to produce ketones to be used for energy – this is speculation though on my part. Yes, there is a down regulation in pyruvate dehydrogenase which helps turn stored carbohydrate into glucose for energy, however the importance of this is questionable given the increased availability of fat for fuel, and there may be other enzymes upregulated to counteract this change in the fuel use. A potential way around this issue (and to ensure glucose metabolism is continued on your LCHF approach) is to do higher intensity efforts in training that force liver to convert glycogen to glucose – thus keeping glucose oxidation pathways high. I’m also beginning to recommend that people take on a small amount of glucose pre-high intensity sessions if they are beginning the fat adaptation phase during a training cycle that incorporates higher intensity efforts. Ideally your fat adaptation phase will occur during base training when we can keep intensity low. But that isn’t always possible. Fifteen-20g glucose prior to training for these high intensity sessions can keep output high but is unlikely to be enough to “ruin” your adaptation process. Again, there is no research behind these numbers, but from a practice perspective I’ve seen this work well.

Finally, you know I’m an advocate of ketones to help support training whilst lower carbohydrate, and it certainly has helped me and many of my clients. We don’t at this point know enough about ketone utilisation in the body and whether taking exogenous ketones downregulates the body’s ability to produce them. This is an emerging field we are looking at with interest with regards to dosage, timing, type of ketone supplement etc. There has been decades of research into carbohydrate as a performance enhancer, and we can probably expect that it will take a few years of research for these questions to be answered in the science research space. Trying them yourself is likely the best approach to see how they impact your own performance (and I can help you with that).

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Plews at Kona (PC http://www.trizone.com.au)