I think it would actually be very difficult to calculate out how much fuel is used in large distant vs small local production. I think that it could go either way depending on how the person chose to calculate it, and the method of calculating could generate a lot of debate.
I don't believe the above formula is complete. I also don't believe the decision of long distance vs local is that clear.
If things are done in huge volume, it is hard to justify local production if you only look at amount of carbon per unit of food based on miles and gasoline alone for that last step of the distribution process.
If you look at a food network that is solely local production, vs mostly very distant, look at the whole process of getting the egg to the consumer.
Even....eggs are probably something of an unusual food product as I think actually, a lot of them are produced in the USA. But I think many commercial eggs are covering surprising distances.
The eggs could even be produced in one country(in some cases, perhaps not USA, but in many other countries), moved to a distribution center in another, and then moved 3-4 times to the final step at the local market, over long distance in refridgerated cars. The supply chain probably involves a number of different businesses, all who have employees and requires buildings, commuting miles for each, etc. They may require some inspection; then the inspector's travel to the distribution center is figured in, all the driving of all the employees to each step of the distribution chain, the power required to maintain each distribution center building, including the electric lifter used to move the eggs into the display shelf at the mega-supermarket, which is probably charged with electricity made at a power plant that burns low grade coal, and even, a percentage of what is required to power the mega-supermarket. You would even need to figure in the road maintenance that is involved when heavy trucks use the road long distance, vs lighter consumer vehicles traveling locally. Long distance trucking puts more strain on bridges and all infrastructure, even including law enforcement(accidents, enforcement of trucking regulations, etc).
Too, most road building materials are petroleum products that have a 'footprint' themselves bigger than Sasquatch.
THEN add in the consumer driving to the store and back!!
The entire supply chain of non local foods is, well, a humongous network of businesses, employees, buildings, trucks, roads and facilities. It is huge.
Even at that, I seriously wonder if people would ever give up all the luxury items they've grown used to, that are a part of the non-local food supply chain. Fifty years ago, the food market was very, very different. I'm not sure it was entirely local, even then, but the number of non local products and the amount of variety really has changed a great deal.
For better or worse? If you calculate the non local food supply chain based on gas per unit of food for that final step of distribution, it might seem better or equal. If you dig into more of the true costs, it is shockingly expensive for the environment.