You will lose a pound if you burn 3500 more calories than you take in. This is one of the bottom lines in weight loss but whether or not you are actually burning 3500 calories varies from person to person with the same activity.
A dog can survive without eating for 14 days, procided day wouldn't be in good shape and health.
Larger dogs live shorter life spans in general so some bigger APBT's/bullies can have shorter life spans. Small dogs like breeds under 30lbs can live for a really long time, breeds like great Dane's have life spans around 7 years. Most dogs will average 10-13 years and APBT's tend to live longer than most dogs. You can go to several sources to find breed life spans but the one I found most reliable is 13-15. Most APBT's in my house and in my dogs lineage have long life spans of 14-16 years my bigger dogs tend to have spans of 10-12. So if they live a healthy life and are smaller the chances your dog will live longer increase.