You might be able to find them at Ranch 99 or Zion Market or another Asian grocery in your area. They're made from Japanese yams.
I'm pretty sure I've seen the prepared stew you describe at ramen or sushi shops.
1) eat real food - more vegetables, moderate meat, moderate fruits, less grains, less sugar, less vegetable oils.
2) exercise - moderate intensity cardio, sprinting, heavy lifting, dedicated stretching and mobility.
3) live - relax, de-stress, meditate.
Disclaimer: I'm not professionally qualified to make any formal recommendations. I've just done my homework and I'm my own guinea pig. All of my data, unless otherwise cited, comes from a sample size of n=1 (me).