If you had become the top-tier predator and scourge of humanity, would you seriously care enough to attack the obese? ...I mean, if you were somehow in a famine situation, sure. Any one of us would do what it took to survive (we're fit). Otherwise? Nah, the prime wolf-pack goes towards the most delicious meat, not fat-as-fuck adipose tissue. Also, the chase is better than the catch. Admittedly, this would involve Friday night beers and cornering random fatties to watch them die from exhaustion after 30 metres, but that'd be for shits and giggles.