If one doesn't care about what they eat, it stands to reason they probably don't care about what they vape...
But, they cared enough to quit smoking. Maybe they care about their health more than you think.
One can eat large amounts of heart healthy fats containing high amounts of omega 3 and 6 fatty acids. They may be overweight and have very high good cholesterol levels, which actually make them quite healthy. The Italian side of my family seems to be this way. Grandma, who once made booze in the bathtub, was quite obese and in good health. She lived into her 90s. Her sister and brothers are all obese, still alive, and in their 90s. Obese does not always translate to unhealthy, or eating McDonalds. Their obesity may put stress on their joints, but their hearts are doing well despite their weight.