Multiple times on this blog I've referenced Gu chomps but haven't explained what these wonderful caloric tasty bites are. So, now I will!
Fuel is important for all athletes. Your body is a temple (or an engine) and all that. But endurance athletes have an additional challenge of needing to fuel during our exercise. For some people, eating while running can be a huge challenge w/ nausea, cramping, diarrhea--> all collectively referred to as "runner's gut". The medical reason is that during running (or any physical exertion) the body shunts blood to the most important areas of the body like the heart, lungs and muscles, leaving the gut w/o its usually blood supply. This is normal and adaptive, but for some people it can be a problem. I actually love the 'gut shut-down' because I would hate to have to stop to go to the bathroom during a race (how gross and inconvenient!) and I generally don't get sick running no matter what I do or don't eat.
There are all kinds of recommendations about when to eat while running, what to eat etc. In general, people agree that for work-outs less than 60 minutes all you need is fluid. Once you exercise for >90 minutes you probably should start ingesting some calories for maximum performance.
Of course, this has prompted an entire industry of sports drinks and foods some designed for pre-workout, others for while working out, others for recovery. There is all kind of talk about when you should intake all carbs (while exercising) vs a combo of carbs/protein (recovery). There are probably world experts in "caloric ingestion peri-exercise".
There are many ways to get calories while running. Most people use sports drinks such as Gatorade (G2 is my favorite, 1/2 the calories and less sweet). Others use gels such as Hammer Gel or Gu (the picture at the top of this entry). Gu gel is basically sugar in a thick gel-like formation. There are even Jelly Belly "sports beans". I used to use the gels before the far superior Gu Chomps were invented.
Gu Chomps (and the almost as good Clif Shot Bloks) taste and feel like super-dense fruit snacks. Plenty tasty and easy to consume on the move because you just pop them in your mouth and chew at your own pace. Depending on the brand either 3 or 4 of them = 100 calories. In general, I usually eat nothing on 10 mile or less runs, 100-200 calories on 15 mile runs and probably around 500 calories b/t sports drinks, goo chomps and bananas/other on course food option during marathons.
I, however, am guilty of one of the cardinal sins of intra-race calorie consumption- I usually wait until I'm hungry to eat. It seems (based on the blogs I follow) that most people eat their calories at relatively pre-determined intervals (every mile, every 4 miles,etc) rather than waiting until they are hungry. Lately, I've started wondering if I should start doing that on 10+mile runs. I do get pretty tired and hungry in the later part of long runs-- maybe I'd be less so if I consumed more calories earlier in my run? I'll have plenty of opportunities to find out as I train for the multiple spring marathons I hope to complete and compete in.
My mid-run bonk a couple weeks ago really convinced me to start carrying calories and water on me for any run that may exceed 5 miles. You just never know when you are going to become desperately hungry or thirsty!