I know there seem to be a lot of similar questions, but most are about pain on the top of the foot. Mine is located on the inside of both feet when I run.

Here's my situation. I am extremely overweight (honestly I weigh around 290 for 6'0) and I have very flat feet. I did go and buy good shoes with thick gel soles (is that the right word? had to translate). The pain occurs only when I run after about 700m and quite rapidly wears off when I stop running. After my jog I feel no pain afterwards so I don't think I'm injured (yet). I also have the same pain in my calves but the foot pain is worse and makes me have to stop running even though I could still run.

Is this a matter of being overweight and having flat feet? Will losing weight make it better, and will I injure myself if I continue to run?