How can I lose 2 kg while training for a marathon?

I am male, 50 yr. old, 72kg.  I am training for a marathon (my 4th), on 18JAN.  Obviously, I'm getting into the really long runs now, but my weight has been constant since I began training in September.  Is it possible to trim a small amount of weight ("spare tire") to boost my performance without working against the training/muscle building?  I currently am eating about 2100 kcal/day, with 300-500 kcal extra on long-run days.  My diet is fairly balanced; previous 6 days look like this: 

Fat - 13.9%
Protein - 21.8%
Carbohydrates - 62.5%
Alcohol - 1.8%
Other - 0.0%

Daily Calorie Intake - 2,139 cals
Daily Sodium Intake - 3,590 mg
Daily Sugar Intake - 109 grams
Daily Cholesterol Intake - 150 mg
Daily Saturated Fat Intake - 6 grams
Daily Fiber Intake - 74 grams

Any suggestions would be welcome. 

I would put money on the fact that you will lose the weight transparently as you start to increase your mileage. I lost between 5-8 pounds eating high carbs and without dieting when I ran a marathon simply because as you start to run for 90+ minutes you are burning at least 1500 calories.

Having said that, if you have already run several marathons and have not lost the weight naturally, you might want to try experimenting. I have not run your numbers through the system to see what your burn is (without the running) but if you have a 300-500 cal deficit on normal days at 2100 calories your deficit on a long run day could be getting close to 1000 calories, no? At that point my suggestion would be to lower the carbs and increase the protein? 

Oh, from personal experience I found that I lost permanent weight when I increased my fat intake, as strange as that may sound. 90% of my food is prepared at home, which means my fat comes from cheese, olive oil, nuts and peanut butter. But I average 30% fat on a daily basis, sometimes a bit more if I have more cheese than normal.

You'll have to be careful with the marathon training and expecting to lose your "flub" from that  - with that amount of intense cardio it will take a tough toll on your muscles! (that means: eat away at your muscle reserves without careful meal planning and balance!!!)

While marathon training you are not likely going to be gaining a lot of muscle... especially while in a deficit of calories. They call running "cardio" and not "weight training" for a reason I guess... :)

You'll be in great cardiovascular shape... but I'm sad to say you probably won't see the muscle definition you are craving from marathon running! (I'm jealous of your running ability! A marathon is nothing to sneeze at)

Are you doing any strength training in addition to the running? If not that might be something to consider.

In general, it's not advised to attempt to lose weight while training. In all likelihood, as long as you are eating "nutrient dense" type foods combined with your exercise regimen, you will probably lose weight. It is pretty doubtful that your performance would improve dramatically if you lost 2 kg. I agree with the person above me about adding strength/resistance training...this could be as simple as holding soup cans and doing bicep curls or as complex as going to the gym. Increased muscle mass leads to more fat burning. Combining endurance exercise with resistance exercise is more likely to enhance your performance than trying to lose weight.

If you still want to lose weight after the marathon, then go right ahead.

Thanks for all the info and suggestions.  I'll build in some strength training and see what happens.