Running Fast or Fasted Running?

Should you go into a workout 'on empty'?

Do a quick google search and you'll find a host of recommendations.

Here's my take, and what I do myself:

• If I have a short (i/e an hour or less) and easy (i/e a recovery spin on my bike on the trainer) AND it's first thing in the morning, I'll do it without having eaten first.
• I will NOT attempt to do anything long and hard without fueling up; everyone is different to a degree and speaking for myself, I perform much better when fueled.  
• I do NOT recommend trying to do the bulk of your endurance training on empty.  

Granted, if you're new to the sport, it may seem foreign to grasp the concept of eating WHILE training as almost ALL of my clients have a hard time getting their head around it.  Particularly if you're someone who is coming from a weight-loss background, you may think 'if the purpose is to EXPEND calories, why would I INTAKE anything'?

EASY- for long bouts of activity, you need fuel.  The better fueled you are, the harder you can go and then. BURN MORE CALORIES, if that's your goal.

Say, for example, you ride your bike for 4:00.  As a VERY GENERAL hypothetical, if you expend 500 calories per hour during the session, and take a gel every 30 minutes (as I do, based on the guideline of 4 kcal/ kg body weight/ hour of exercise), you'll have consumed nearly 1,000 calories, but you're still in a deficit of 1,000.  If you had NOT eaten anything, you may have slowed way down or bonked and the ability to burn calories would've been far diminished as a result.

The best thing to do is try a very short session on empty, if you're interested in doing this experiment, as see how your body reacts.  Again- do it under easy conditions as listed above and don't attempt to climb Everest on empty!  Not that I'm planning on learning how to accomplish a feat like that, but you get the idea!