Nutrition is a much more complex thing than simply counting calories.
An athletic bloke should be eating the calorie count of his BMR based upon the weight he wishes to be. However, the weight he wishes to be is not necessarily what he reads on NHS posters or leaflets. An athlete's ideal weight is low fat % ( around 8% for a pro cyclist ) and lots of muscle where it matters for the sport he's participating in.
Using the guy's height and frame dimensions ( wrist circumference ) and desired fat %, a base weight can be determined. Then, an approximation of desired muscle mass is added and his diet calculated.
For a starter, he will be consuming 2 g of protein for every 1 kg of lean muscle mass he is attempting to achieve.
Secondly, he will consume the required CHO for sporting muscular activities during the next 24 hours using the 10,000 calorie 'sliding scale'. And some fat, approx 10% of the total calories.
If the sport requires heavy muscular activity, which cycling does, he should never deter from the protein intake.
A BMR of 2000 calories for an average man will keep him alive with the inclusion of everyday activities such as washing up, pushing a vacuum cleaner around for half an hour and ironing a shirt or two.
Deliberate exercise ( the cycling, gym work or jogging ) energy requirements should be calc'ed as per my 10,000 calorie 'sliding scale' chart.
I cycled 46 miles yesterday and my overall total calorie burn was 3100 kCals. 1050 kCals of extra food was plenty enough. My BMR is 1700, so Saturday evening and through Sunday, I consumed 2750 or thereabouts.
H2O is 1cm^3 per 4 calories ( based on total count ) and NaCl is 1 g peg 1000cm^3 H2O lost from the body.