I'm going to be going on my very first metric century this weekend. One of the issues I've dealt with on long rides (50-55mi) in the past is running out of energy and water, so this time I made sure this route passes through a few small towns that have food/water for sale.

I noticed one of the towns I pass through has an Arbys on my route, and I was wondering if it would be a good idea to stop in and get a roast beef sandwich with cheese? Here's my thinking:

Roast beef: protein and potassium
Cheese: sodium and fat
Bun: carbs for energy

It seems like it would be a good idea to me. Is there anything I'm missing? Is this a bad idea? Are there better alternatives?

If you have to eat at Arby's, stick with the regular roast beef, no cheese. There's plenty of sodium in the beef, you have plenty of fat on your body. You don't burn ingested fat anyway, it all comes from your "stores".

No. More than a small amount of meat on a ride is a bad idea, unless you are going slow. When you are working hard your stomach doesn't digest things well, and meat is difficult to digest. I have seen guys eat half a roast beef sandwich on a ride and then feel bad and go slow for the rest of the ride.

Eat something that is easier to digest. Pro racers will sometimes have a ham sandwich during a race but that's a slice of ham, not a whole pile of meat.

You can find better choices at a convenience store - granola bars, banana, chips, cookies. Eat small amounts often, rather than a big sandwich all at once.

When I ride, I don't need much additional fuel to keep me going. I banana is good (but they get kinda funky in a jersey). But almost any fruit will do as does dried fruit. As mentioned above, convenience stores are good sources of stuff. Valygrl is right, eating more frequently and smaller amounts will work better than a big feed.

Ok good to know!

Convenience stores are a god send. My group ate once at a McD's after a climb and I felt like crap for an hr or so afterward.

Regarding Arby's on a ride? Do not do that to yourself. After the ride? Don't do it then either.

Don't forget the large order of chili cheese fries and large chocolate shake.

I remember when our club put on our first double century ride. It was just for club members and we had a group of about 20 riders. Had a couple sag vehicles that were well-stocked with the usual bananas, oranges, energy drinks/bars, PBJs, etc. and they stopped every 30 miles or so to let us refuel. At about the 170 mile point the sag car had pulled into the parking lot of a Stuckey's restaurant. It was a hot day with temperatures above 100F and the last part of the ride was into a substantial headwind. All of us rode right past the sag car and piled into the Stuckey's. We were so sick of the 'proper nutrition' that we ordered burgers, large fries, and chocolate shakes. Picked my spirits right up and the last 30 miles seemed to fly by.

Newer riders tend to have a problem digesting food while riding. More experienced riders do better. It also takes some practice.

It's not a bad idea as long as you throw away the beef and cheese and just eat the bun.

You need carbs, not protein or fat during the ride. You might tolerate it and enjoy the meal but it won't help your performance on the bike. Put some gatorade or sugar & lemon juice in your bottles and bring some snacks high in carbs. Aim for 250-300 Cals/hr of carbs and you should be good to go.

One caveat - running out of energy during a ride longer than you're used to could be due to nutrition or lack of fitness. Obviously all the food in the world won't fix the latter.

You may also find that different types of foods help at different parts of a ride.
Once I hit a certain point my stomach detests solid foods. At that point I switch entirely to liquid nutrition like gels.
I have a twitchy stomach and figuring it out is quite the chore.

It is never a good idea to eat at Arby's.