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Nutrition

The low-carb debate: good or bad for athletes?

Does trying a low-carb diet, with the hope of making your body adapt to carb depletion, work? Renee McGregor and Alice Hector debate the issue

THE NUTRITIONIST

Renee McGregor is a registered dietician and sports nutritionist

The debate around a low-carb diet has been around for a few years now, made very popular by the ultra running scene. The theory suggests that if you follow a low-carb diet then your body has to use fat as its preferred fuel source. Many individuals have claimed that switching to a LCHF diet, where carb intakes are no more than 50g a day, has had huge benefits to their performance. But, when you look closely at the actual scientific studies, it’s not quite as simple.

Scientifically, we know that our body actually uses a mix of both fat and carbs for fuel; relying more on fat stored in the muscle in low-to-moderate intensity training. We also know from numerous studies, that as exercise intensity increases, i.e. above 65% of your HRmax, the body needs carbs in order to maintain these faster paces. But this doesn’t mean that we suddenly stop using fat for fuel, but the body will rely on carbohydrate, which can be broken down into glucose and delivered to the working muscles quickly and efficiently. 

In actual fact, it’s endurance training and some manipulation of your diet that actually improves your ability to oxidise fat for fuel, not just removing carbs from your diet.

Professionally, I don’t advocate the use of HFLC diets and feel very strongly that such a regime should not be sustained for long periods of time. It’s still a relatively new area of sports nutrition and so the effects on the body are not fully understood. But we do know that insufficient carbohydrate intakes in athletes can lead to a depressed immune system, over-reaching and over-training syndrome, as well as changes to hormone and bone health. 

My advice would be to follow a more periodised approach: include carbs around high-intensity training and aim to do low-to-moderate sessions in a carb depleted or fasted state. This is both sustainable and helps keep training consistent, which results in progression.

THE ATHLETE

Alice Hector is a long-distance pro and ultramarathon runner

In 1879, explorer Frederick Schwatka and his team set off on a record-setting 2,709-mile sled journey across the Arctic. To fuel the arduous 11-month expedition, the men killed and ate reindeer, polar bears and seals, i.e. a lot of fat and practically no carbohydrate.

Schwatka initially noted in his journal “an apparent weakness and inability to perform severe exertive, fatiguing journeys.” But three weeks later the feeling disappeared. The reason? The low-carb diet had forced his body to adapt and use fat as its primary fuel.

As for triathlon, using fats as fuel brings a number of advantages: no more sugar spikes, a steady stream of energy, no endless gobbling in races and minimal risk of stomach upsets. It also has good long-term health implications through the control of blood sugar levels.  

The problem is that adaptation takes time. Fat is our protective survival blanket and your body will not let it go easily. Even when adaptation takes place, high-intensity sessions with low carb stores will make you feel as flat as the pancake you never had. Certainly in high performance sport, I believe carbs are absolutely necessary. They are the muscle’s fuel after all.

 That being said, getting yourself used to carb depletion is a vital part of training. We can’t possibly get all the fuel we need from carbs alone when we race. So we need to optimise availability of our endless fat stores. Here are some tricks of the trade: 

Do some fasted sessions before breakfast (nothing too long or intense); minimise fuelling on some longer bike rides and runs (but always carry an emergency something!) and kick-start fat-burning that way. When you get in from that session, have a decent carb/protein mix to recover properly and ensure that the next training session is of good quality. If training isn’t too intense the next day, have a low-carb evening meal.

Related

Carb-free diet: good or bad for athletes?

Five tips for low-carb training

Train carb-free to boost your body's fat-burning ability

What is 'carb cycling' and is it suitable for triathletes?

Carb Loading

Sport nutrition: could carb-loading be at an end for triathletes?


 
 

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Jon Wickett

A nice article, thank you. I think it's important to consider the health benefits of lower carbohydrate lifestyle esp for masters athletes. Older you get the more likely you are to be less tolerant of sugary foods e.g. if you grew up in the 70s and ate Frosties every day! Many athletes claim to experience higher energy levels and faster recovery on low carb.

Stylsie

I think it's very telling that Tim Noakes was shown online symbolicly ripping out the carb up section of Lore of Running. 

 

I have far far too much timber around my middle, I've turned to triathlon (and been bitten by the bug) to help with weight control.  I've also been looking at nutrition closely and there is no doubt in my mind that personally I "work" better with a LCHF or Banting type diet. 

 

The rabbit bit hole runs deep and im not convinced that dieticians have ben given the full story over the years. Many of them find themselves entrenched in a position they've been in for years and are reluctant to do a uturn on advice they've been given for years. 

Stylsie

Renee McGregor opens up by saying:

 

"The debate around a low-carb diet has been around for a few years now,"

 

Seeing as modern day carbs have really only only been around for a few hundred years (it could easily be argued that genetic modification in recent times means that they have not even been around that long) whereas man has been around for 200,000 years (ok, that figure could be argued either way, but certainly we've been around for longer than granola. 

 

as we haven't gone extinct in that time, does it not stand to reason that are bodies are more than capable of existing without convenience carbs?

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