I took a big chunk of time off the bike, but as of about 3 weeks ago I have been slowly putting in some mileage (20-30 mile rides, a few times a week). I'm not in great shape right now, but I did a ride yesterday which I thought was pretty awesome from a performance standpoint. Not performance being viewed by how fast I rode or by the average Watts I produced during the ride, but by the way my body was able to produce the necessary energy to complete the ride.
My diet hasn't drastically changed over the past few months, but I have modified it somewhat in order to promote optimal health. Without getting too specific, I have greatly reduced my total consumption of carbohydrates/sugars (simple and complex), maintained my protein intake, but increased my consumption of dietary fat. I've actually increased my calorie intake, but I'm not gaining weight in the process. What I've done from a physiologic standpoint is modified my metabolic (energy producing) pathways to use fat as a better and more efficient substrate for energy production. Our body (specifically our liver) can produce, from fat and some amino acids, 3 main ketone bodies. These ketones can be used to create energy for our brain, muscles, ect. So essentially, you can teach your body how to burn off fat better through diet and exercise intensity level, while positively influencing other aspects of health within your body. (not for this blog post).
OK, enough science! Why am I bringing this up, and how does it relate to my ride? Yesterday I did a 50 mile starting around 9am (furthest I've ridden in a long time). I rode with 2 other friends, but was only in a drafting position for about 10% of the ride. I finished the 50 miles with an average speed of 19.8MPH, and 2,800ft of elevation gain. That's not necessarily impressive in and of itself (at least to me). But what I found to be interesting, is that I didn't eat anything for breakfast (had a couple sips of coffee w/ no sugar), I didn't bring any gatorade/sugar-hydration (just water), and no supplemental forms of energy (e.g. food, gels, bars). So I did just over 2 1/2 hours of moderate intensity riding (I didn't wear a HR monitor, but I would guess I had an average HR of 125-135bpm) without any breakfast or energy supplementation during the ride, and I felt like I could have ridden another 20 miles or so and been fine. I would say that my body is getting better at creating energy through metabolism of fat substrates and sparing my stored glycogen (sugar).