Training for the Marathon has made me gain weight :(

Water retention for repairing your muscles/other causes.

this!
Probably retaining water.

Look at it this way.......you are shirking ! Everyone around you can see your *kitten* getting smaller but only you can see the number on the scale!

You've lost an inch off your waist and your calves are rock-solid...and you're complaining? Buy yourself some flowers instead, make sure you're fueling your runs properly, and keep going!

It normal. It did the same thing for my first ½ marathon…, It will come back to normal. Just try to find balance between giving what your body needs versus over eating... it easy to over eat when you come back for a long run. We all do it. Keep up the good work end enjoy the experience!!! And drink lots!!

Wait, you're getting smaller and weighing more, but you don't think you're loosing fat?

Forget Ugly Crappy Kilo measuring devices (scales)... Is your pulse rate lower? Is your blood pressure lower? Are you faster? Are you leaner? Do you float lower in the water? Are you wearing a smaller size? Are your clothes looser? Forget the scale and focus on your health at this point!
From your pic, you look like an attractive young lady that is light enough for her height and is working on being ultra fit. DO NOT let some piece of metal with a digital or analog read out take the bliss you should be feeling about who you are and the healthy you that you are striving to become!

I have a buddy that did marathons and learned a couple things (hopefully they are accurate). He ran a lot and had a little fat on him but oddly body doesn't burn much fat when running. Major fuel source is carbohydrates stored in liver and muscles called glycogen. This also takes up a greater amount of water to fuel body. Storing extra water and fuel would cause a weight gain as body adjust to endurance running. My friend would carb load night before run to max out storage levels. Best ratio to replace glycogen is 4g carbs:1g protein. So extra water and energy storage plus extra muscle is what body requires.

I watched a documentary on sedentary people picked to run Boston Marathon training over 10 months. They had medical evals and VO2 max tests and whole 9 yards. 1 very over-weight person lost some weight but all. Overall moderate weight lost at best. Surprise was that least VO2 max at start was equal with everyone else in like a month. Only 1 injury caused someone to drop out. Everyone else finished the marathon.

I agree with this person. Every time I train for a marathon, half marathon, etc. I gain weight. Its normal. Your body is trying to store more glycogen and glycogen is stored with water. That itself would make you gain a couple of pounds. Running burns carbohydrates reserves. When you train, your body tries to store as much carbs to fuel your long runs. Also, people tend to be way hungrier when they increase their daily runs. Another thing is muscle. I'm sure I gain muscle when I train. I can feel it.

Don't worry about the scale. I know its hard. I worry a lot about the scale and sometimes in inhibits me. Don't let that happen to you. You are becoming a stronger and fitter person and that's fact. Believe that and move on. Also, you will lose a bunch of weight just after your run. After the event and you stop training like crazy. You will lose all that water weight, glycogen stores etc and you will suddenly lose a lot of weight within 1 month. That always happen to me. You will be leaner and you will be left with the muscle but none of the other components.