Never said cyclists don't use less energy. They use less energy, but they use it terribly inefficiently. And no, nobody burns "excess calories that they would have already eaten". The reason you get hungry after exercise is because you're burning calories. If you start burning an excess of calories and never eat more to compensate, you will starve to death.
If you ride your bike an hour, you'll burn about 500 calories. If you drink two beers worth drinking, you'll consume 500 calories. The average person has a pretty large variance in caloric intake and an hour exercise isn't going to change the food distribution of the world. So it's not a stretch to say that extra food consumption from cycling isn't going to affect the environment at all, when comparing to moving a 1000 kg car with the 90 kg person inside it going the exact same distance with the goal of getting that person from point A to point B. Nor is a single person driving a car, I think we're in agreement on that. The cyclist commuter wins easily. Especially if you go back to the petrol and car supply chains like you did with cyclists food (after all, oil wells don't drill themselves, nor does gasoline refine itself, nor do cars spring magically from the earth...all of these require tremendous energy.
And of course it's risk of death per mile that matters, not per time or per number of trips. Are you going to quit your job and pick a job closer to your home when you switch to the bike too? You have the same destination as in the car, just a different mode of transportation. You have to do the same number of miles.
This would be true if all miles were the same, but they aren't because of hills. My 10 mile bike ride takes 45 minutes where it would take me 30 minutes in Florida. Plus, probability math would use a timescale, not a distance. More important considerations would be the road configuration, traffic per lane, clearance between the car lanes and bike lanes, and the blood alcohol content of the driver and cyclist. Apparently it's more dangerous in the UK than the US, our fatality rates are 1:2. Clearly the UK roads are more hazardous to cyclists than American (because I know that the Brits drive better than we do).
The average Briton cycles 53 miles a year. The average number of car miles is 8200 - 155 times more mileage. Looking at the same year's accident statistics, 801 people died in cars and 8232 were seriously injured. 110 cyclists died, 3222 seriously injured. That's 7,3 times more deaths and 2,6 times more serious injuries for cars... which go 155 times further. Even if you factor in 100% of pedestrian deaths to cars (and hey, are we forgetting that we still need goods hauled around?), they're only about half of the car casualties, so it doesn't even bring the numbers close too each other.
Sorry, bike nuts. Your mode of transportation is horrible for the environment and horribly dangerous per mile. So stop trying to make us all take part in your stupid hobby.
By the way, I'm not saying don't drive your car, I'm just calling BS on saying that cyclists are less efficient than cars when considering commuting. And it is more dangerous, but not extraordinarily so.