I walk regularly, and have worked up both distance and speed; recently joined local gym for strength training 3 days a week. Helps keep the heart healthy and the blood moving; fewer problems with feeling cold (including feet).

On a more serious note, as we age our thyroid can begin to "peter out." Lower thyroid activity can cause one to feel cold in "normal" room temps. A talk with the Doc may be in order...(been there, done that).

If all else fails, try Grandma's remedy---put on a hat; its like putting a lid on a tea kettle, keeps the heat in for use by other parts of the body, including the feet.