Many runners do not lose any weight while training for a marathon, due to large number of calories they consume during the "recovery meals", taken after a given workout (To be sure, some believe that cutting calories during marathon training is an invitation to injury).
Ewart Harris writes,
I would guess you should consume an amount that will allow you to keep within your daily limit. Remember that you need a calorie deficit in order to have weight loss. The amount you take would also be dependent on the duration of your run. I estimate that I burn approximately 100 calorie per mile (It does not matter what speed you ran at). I estimate that I need approximately 2200 calorie for just normal daily living to maintain my current weight (that is without exercise). Depending on the number of miles you do, example say a 10 mile run will burn 10 *100=1000 calories. I would add this to the 2200 to get (2200+1000 = 3200 calorie for that day to maintain weight) I would suggest you then take away 500 to allow for weight loss. This means that you should limit your intake to 2700 calories for that day. The reality is that weight loss will not be so straight line but if you track your calorie intake like this, over time you should see yourself losing weight.
After a ten mile run you could maybe take in 250 to 500 calorie in chocolate milk. Your personal preference for other foods would determine how much calories you want to take in this way. Additionally, you need to get in other nutrients that you do not get from CM. Try not to go over your calorie limit as you will not lose weight. I know some folks who use to post here who would drink a litre or more of chocolate milk after their long run (20+ miles). But I would caution against that as I think some people just find it more easy to lose weight than others.
Basically, what I am saying is that you have to gauge this considering your other dietary intake. If you go to the NIH (national institute for health) of CDC website they have very good guide lines on daily intake. You could use this as a guide. I hope this helps, or others might chime in.
PS my kids swim alot 6 hours per week. They are 8 and 9 YO I give then each about 250ml and a banana after each practice. Swim Ontario also recommends it as a good snack and recovery drink for swimmers.
Ewart's public profile on active.com can be found here.