You can work out a lot and lose weight, but what matters is how you feel. Many people who work out a lot or are thin, get winded after some dancing and running. Do you? Can you hop out of bed in the morning? Can you come back from disappointments? How are your energy levels? And no, you don't need vitamins most likely. Check in with yourself.
Remember, fitness is endurance, strength, flexibility ad of course organ and blood health. Energy manifests this to an extent. Just today I heard people talk about the strength of the Olympic US ad Russian top men. How do they rise 17-21 inches off the ice after a triple axle? They mentioned endurance, strength (power) and flexibility, and core strength exercises (like Martha Graham classes).
Disclaimer: None of the above information can be taken as a substitute for advice from a medical professional such as a physician.
My third book, Pocket Guide to Fitness, is available on www.louizapatsis.com, http://www.authorhouse.com, www.bn.com and http://www.amazon.com. If you look up my name on those Web sites, you will find my other books The Boy in a Wheelchair and Life, Work and Play: Poems and Short Stories.