What Lustig doesn't mention is that sugar is what your brain runs on. Eating too much sugar is not good for actual marathons but it works great for coding marathons.
Do you have a source for this? As far as I am aware your brain mostly burns glucose like the rest of your body. Admittedly glucose is also a sugar, but in the context of this talk sugar refers to sucrose (i.e. the white stuff you put in tea) which is 50% fructose, 50% glucose. Which would imply that sugar is still inefficient "brain fuel" compared to other carbohydrates like pure glucose. If you have any sources/references showing me wrong about the brain metabolizing fructose I'd be very interested and grateful if you could point me to it.