It was just an off the cuff remark.
They are running 48 miles a week but are only consuming 300 calories more than the sedentary group over that week.
It would be fair to suggest they need a higher intake of protein (and carbs) than the sedentary group because of muscle wear and breakdown during those long runs.
It was also wrong to say eating 50% more than the daily calorie intake will cause someone to become obese.
Check out Michael Phelps' olympic diet , he is eating 12,000 calories per day which is around 4 times the recommended intake.When you are doing 8-9 hours swimming you need some serious fuel , low protein rabbit food won't cut it.