Training in Ramdan...

Sallam brother,

I run track and I train through ramadan. I have never missed a day of fasting since I started running track alhamdulilah and train about 5 days a week track workouts and weights 3 times per week on average. Ramadan is a great time to train!
Inshah allah this blessed month will give you the results you want. Ramadan is not a time to sit around because we are fasting, ramadan is a time to go out and live our lives to the best of our ability doing all that we can. As long as your training does not compromise your fasting you should be fine. If I can do it I am sure you can too! I push myself harder and ramadan and I am always at my best during our holy month. You can as well! Pray for strength and you will get through it. It is tough at first but the mental toughness and self discipline you get from training during ramadan is unmeasurable.

Bismillah,

Even athletes end up eating less than their normal amount by the end of Ramadan naturally.  But you must understand weight gain is related, usually, to the amount of calories you take in compared to those you burn up in any type of activity.

So, briefly, I would say to make sure to get plenty of water when you are not fasting (during the night), and eat at least two good meals and a healthy snack, like grapes or oranges, if you stay up late.  Get plenty of rest too for all of that running.  May Allah, SWT, accept your fast.