Commenting on cycling my wife often says I am a product of my era, a time of cow-horn handlebars, gear shift paddles on the down-tube to flick between the extensive choice of five gears, a time well before carbon frames and sports nutrition. Long endurance rides were sustained by a convenient stop and a pie and a pint. Anyone drinking shandy or a soft drink would be branded a puff and was expected to bonk before completing the ride. No sympathy.
You ride, you burn calories, you use the reserves in your body (e.g. the five pints you had the night before).
Ultimately your reserves will run out and if you don’t add some calories back into your body then you’ll hit empty. You’ll bonk.
Lets say I’m a commuter, I ride 10 miles to work each day. I could probably ride 20,30 maybe even 40 miles without being overly tired. Beyond 40 I’d start to struggle unless I had a rest and a bacon buttie* (*or alternate sport-gel-food-substitute). That buttie might carry me on for another 25-30 miles. Then I’d start to struggle. Big time. Even beyond rescue of steak and chips. By this stage I’d be hitting zero, why? I left it too late.
When should I eat?
Your body takes time to digest food and turn it into the useful energy you need. You need to be eating before you become desperately hungry.
Also you should bear in mind that your stomach demands blood and energy to digest food - if you eat while you ride you may need to ease off the pace a little while you're tucking into the goodie bag.
Advice? when you’re out on the bike, eat small amounts and eat regularly in preference to infrequent big feeds.
How much do I need?
It’s a very personal thing, above all though it depends on how far you are pushing outside your comfort zone. Whether it is faster, further or higher you should think about fuelling your body for the extra you are demanding of it.
As an Example
On a long or hard ride* I expect to need to eat and I start after about 45mins. I aim to eat every 45mins, a small piece of flapjack, a gel or a snickers. Often I’ll have the snickers in two halves – easier to digest. I tend to mix it up a bit between gel and solids. Main thing I think is to keep it easy for your stomach to digest.
*’long’ and ‘hard’ are relative to your ability and fitness. You know when you’re pushing your boundary, equally you know when you’re not. ‘Regular’ rides don’t count as long/hard… ‘cos your used to them!
Like I say, this isn’t really my field of expertise. I’ve learnt the hard way over the last couple of years that eating really does help on the long rides. Of course, if you are riding to improve fitness, lose weight etc then packing in the mars bars isn’t going to help. It’s up to you to decide what works for you.
All of the above equally applies to hydration. Lack of fluid is just as likely to kill your performance as lack of food. so keep drinking too!