Thanks all for your input.

I've learned that I'm not eating enough before the ride. I also need to eat more REAL food during the ride rather than the short bursts of sugar. I can see how that can bounce my glucose/insulin levels up and down like a horse on a merry-go-round. I also need to increase my distances during the week on my Tuesday and Thursday rides.

As to how hard am I riding, I am pushing myself the entire ride. I'm not going as fast as I can during the entire ride, but I'm riding harder than what I would call conversational riding (riding while able to have a casual conversation). The only hills I have are the causeway bridges I go over, otherwise it's flat. The wind is usually 10-14mph (and a bit stronger during most of the ride when I'm on the barrier island). Most of the ride is north and south rather than east and west. Most of the time, the wind comes in from the north (which I appreciate during the return). At the halfway mark, I rest for about two minutes and I usually feel good. At the end of the weekend ride, I'm definitely ready for it to be over. My butt and legs are sore, but I can still function the rest of the day.

I thought I may be mini-bonking because I was riding harder and harder, yet going slower and slower for about four or five miles. But the more I think about it, I think it was just a low glucose level due to what happyscientist said. As soon as I turned the corner and headed west, I was fine (the wind was coming off the ocean from the east on this weekend's ride).

What kind of shape am I in? I'm almost 50 years old and significantly over weight. I am about 60 lbs over weight, down about 15 lbs from last year. My goal is to lose another 30 lbs this year, as my diet is significantly changing now. I do have one problem with the PBJ sandwiches. I no longer eat any wheat products. So sandwiches are out. Any bread, pasta, crackers, etc. cause me uncontrolable cravings to eat more carbohydrates.