There can be no doubt about the problem of the epidemic of obesity that is having significant impacts and costs on society and triggering debate over who should be meeting those costs. On one hand, society has a responsibility to its citizens, but an individual also has responsibility to not be burden on that society. As part of that is a physical activity program to reduce the risk of that burden and its complications. Obesity is a significant risk factor for a wide range of problems from osteoarthritis to diabetes mellitus to a number of cancers. Physical activity is going to reduce that risk, and for some, running will be a part of that program.
However, as the main issue in overuse injury is the cumulative load on the tissues beyond what they can tolerate, obesity is going to be a significant additional load on those tissues in addition to the load placed on them by the physical activity. Obesity has been shown to have significant impacts on the foot and foot posture to further complicate this. The management of a running program for someone wanting to loose weight is going to be complicated by those additional loads. Strategies are going to need to be put in place in teaching them how to run properly, so that the load in any problematic tissue is reduced, or at least adapted to over a prolonged period of time (longer that would normally be expected in a non-obese beginning runners). Foot orthotics are good short and long terms means to reduce load in tissues that are at risk for injury.
It has been shown that increased body weight is correlated to increased muscle activity, which is going to potentially put those tendons at risk of injury if they are not adapted properly. However, another study found no correlation between BMI and overuse injury, however these were not beginning runners.
Obesity will continue to be a challenge to society and to those clinicians that manage overuse injuries in them.