A recent study by Gallup-Healthways Well-Being Index has shown that obesity leads to increase pain. Obese individuals suffer 68% to 254% more pain than normal sized people. These results are pretty surprising and should help motivate the overweight to start dieting.
If you are having trouble losing weight, consider training in martial arts, especially BJJ. Early data from my weight loss study suggests that people who train in martial arts have less difficulty losing weight and are more likely to keep it off.