Episode 3 - Revenge of the Fatty Acids
For many many years muscle glycogen and the need to always make sure your muscle glycogen concentrations are high has been king in sports nutrition. This goes back to some of the classic works of Bergstrom et al. in the 1960’s and David Costill in the early 1970’s. Since these times vast swaths of scientific and non scientific literature have told us we need to eat lot’s of carbohydrate to maximise exercise performance because we need to make sure we have sufficient muscle glycogen concentrations. The key word I just said was performance, because maybe, just maybe when you train it isn’t maximal performance you need but maximal adaptation.
There have been many attempts to knock carbohydrate from it’s throne over the years. In the late 90’s, early 2000’s eating a high fat diet had a go. It seemed promising, with a clear increase in fat oxidation when you eat more fat in your diet and improved time to exhaustion, but very rarely an improved time trial performance.
Then in 2005 an interesting study by Hansen and colleagues showed that training in a glycogen depleted state increased fat oxidation during exercise and subsequently an increase in “endurance”. This study was followed up by a series of studies (by groups in Australia, Birmingham and Liverpool) which took real life models of training (the Hansen study was leg kicking exercise) such as cycling and showed that training glycogen depleted increased fat oxidation during exercise. Not only that there was a whole raft of molecular changes within the muscle which accounted for this increase in fat oxidation. However, there was little difference in performance in these studies. It is possible that in performance trials on a longer duration these performance effects may show through.
Other studies have also come out which have shown beneficial endurance adaptations from fasted training. This may also be more practical for athletes to do rather than to actively deplete themselves.
However, what do athletes do in practice? Well they have been training fasted for years and years so this is nothing new. Go to any running club and speak to the experienced marathon runners. The long Sunday run has been performed fasted for generations. Alongside this if you look at the research on what athletes already do then many get nowhere near the recommended carbohydrate intakes. Instead of suggesting that athletes need to eat more carbohydrate, maybe they are showing us that they have found the optimum way of eating to adapt from training. Potentially, naturally training in a fasted state or glycogen depleted state. Let’s face it if you train 6 hours a day there is a good chance you will train in a depleted state.
For me over the last four years fatty acids have started to get their revenge on carbohydrate. We don’t need to be fully fuelled for every training session, sometimes it would be good to train once or twice a week in a fasted state. Or go for a ride without eating loads of carbohydrate. This area of research continues on the theme of asking the question what do I need to eat to adapt from this training.