Cycling uses about 500 calories © an hour at 20 km/hr.
100 km bike ride takes about 2,500 c.
Studies show that in the west for every 1 c of food on our plate it takes 10 c of oil to produce, transport, cook ect.
so a 100 km bike ride would need 25,000 c of oil for food to provide energy.
1 liter of petrol has about 7,536 calories in it.
100 km bike ride would use about 3.3 liters petrol.
the average car using 10 liters 100 km would use 75,360c of oil to travel 100 km.
4 people traveling in a car would use less oil than 4 cyclists.
Im sure different figures can be found but you get the general idea
Of course this dosent include a lot of factors such as manufacture of cars & roads, pollution, congestion and all the other vallid points for bike travel but highlights we need to look at more than just bike riding.