IMO, if insurers would adjust life and health insurance premiums and coverages based on percentages of overweight a person is from standard height/weight charts, there would be an incentive to slim down.
If someone is 50% overweight, they ought to be paying at least 50% more in insurance premiums.
And if a person participates in sports, they ought to be paying more in insurance premiums as well. After all, they get 99.9% of the sports-related injuries.