Body warmth = healthy... but how?

Every healthy looking person I know has a warm glow about them(they also are warm to the touch), almost like there body temperature is higher especially at the skin level. I also notice when I am warmer feeling that my eyes are not red and I feel healthy and flexible, but usually I am cold feeling and have dry/swollen skin. What I am wondering is why and how can I make my body naturally warmer?

Are there any herbs/techniques that naturally sustain warm body temperature?

Please don't suggest things such as warm showers, and exercising as they are only temporary warmth of the body.