I've lost weight from training for a marathon in the past, but I was also meticulously tracking every bite of food that I ate (and would run extra if I wanted to eat more).
I used the Nike Running App or MyFitnessPal during my marathon training, and while both are great apps, they can differ by a few hundred calories when estimating what you've burned. It's super easy to overestimate how much you're burning and underestimate how much you're eating, so it's important to be mindful.
Image Source: POPSUGAR Photography / Sheila Gim