A good reason to get outside and top up vitamin D levels!
According to a University of Florida study, higher levels of vitamin D may decrease pain and help mobility in obese individuals’ with osteoarthritis. Results in the January issue of The Clinical Journal of Pain shows that those obese patients with osteoarthritis who had normal vitamin D levels could walk, balance, rise from sitting to standing better than their obese counterparts who had lower vitamin D levels.
256 participants took part in the study, and from that, 126 were obese. Among those 126 obese participants, 68 were vitamin D deficient, while only 29 of the 130 non obese participants were vitamin D deficient which suggests that obesity is significantly linked to vitamin D deficiency
Vitamin D is stored in the liver and human fat cells and other studies have shown that the larger fat content in obese people can make vitamin D be stored, rather than distributed around the body. Interesting, as obesity is linked to vitamin D deficiency, knee osteoarthritis pain and poor functional movement.

As Vitamin D supplements are cheap and easy to buy therefore, older obese patients with chronic pain whose vitamin D levels are low could benefit from taking a vitamin D supplement and have exposure to the sun as long as they are sensible. It is useful to get 20-30 mins of sunshine out of the peak sun without suncream and then apply at other times throughout the day.
Gentle exercise such as walking is good to start with and you can build up to longer and faster walks to burn up more calories and at the same time obtaining vitamin D from sunlight.
http://www.mind-bodywellness.co.uk/nutrition--diet.html