My own experience has shown that my pain has lessened some (2 neck operations for herniated cervical discs) and almost completely gone away in my right knee, after losing (and keeping off) 125 lbs.
Studies show that:
In particular, in some studies increasing BMI has been shown to be an independent risk factor for subsequent back pain (12) and knee and hand (8) osteoarthritis. For these conditions, there appears to be a dose–response relationship such that higher levels of BMI lead to a subsequent increased risk for pain (12).
A vicious cycle of pain, reduced activity, “emotional” or bored eating, depression can occur. Breaking the cycle is hard. But we know that walking generally improves knee pain. Exercise is as effective as many antidepressant medications. In severe cases, surgery such as total knee replacement can give people their lives back and help them be more active.
Poor sleep promotes overeating; pain can make sleeping difficult, in addition to the sleep apnea that many obese people have (I used to have it, and use a CPAP breathing machine).