I don't actually commute to save money. I do it for the ride and exercise. But the cost savings is definately an side benefit.

I have to own a car anyways, so I can't claim insurance, taxes, etc.. as a savings. It's a issue of the cost of gas, wear and tear on the car versus the wear and tear on the bicycle. (They've both been long paid for.)

Looking at the cars bills and figuring the gas cost for mileage I ride yearly instead of driving, it's probably in the $800-$1000 range for the car. While I haven't spent one penny on the bike in the past three years. I don't have the upgrade obsession that some have.

As far as increased food for energy. I don't see it. At 5'10" and close to an eight of a ton, I could probably cut back on food and still ride.