Cinnimon -your mother is taking crap. I'm running 50 miles /80 km a week ATM and I've not lost an ounce. Apparently 80% of people training for a marathon don't change their weight at all, while 10% gain and only 10% lose weight. If you are training properly for a marathon you would usually be running 75 miles a week ( 3x race distance ) at least .
No way could you lose 5 stone by exercise alone, let alone by running only 15km a week , which probably burns 750 calories in total . That's not even a small kit Kat a day, is it?
Losing 5 stone is a tremendous , life changing achievement and you deserve a lot of credit for it. I'm sorry anyone is trying to take that away from you. Let alone someone close to you .
I wonder if she is trying to say " well i can't lose weight because I can't run /exercise because of my bad back /leg/heart condition /under active thyroid /whatever so it's not my fault " . Usually when people make these ignorant comments it's not about you, it's about them.
No wonder your DH tries to defend you