As any endurance athlete knows, everyone burns 5 calories per liter of oxygen. Genetics, race, sex, age, all have no effect on that. Ultimately your body must adhere to the laws of chemistry and physics. If you burn more calories than you take in, you lose weight. If you consume more calories than you burn, you gain weight.
For example, a 155 pound individual running on a 60 degree day at a pace of 7.5 minutes per mile without wind and on level terrain, will burn a net of 108 calories per mile regardless of their genetics because the physical laws of the universe requires that much energy to move their body at that pace over mile.
Some people rationalize a lot of excuses on why they cannot lose weight or why they are not in better shape, or why various entirely preventable diseases afflict them. I have have a daughter with Cerebral Palsy. She has no use at all of her right arm and little use of her right leg. Despite that she runs cross country and is on the local swim team. Just last weekend she got out and ran 6 miles with me. If she can be strong and fit, then just about anyone outside of a wheelchair can be. Its all a matter of choosing to make those life choices.