Is marathon training good for my body?

Possibly: The only caveat is if this training is new to you i would suggest you be cleared medically from a cardiac standpoint before starting training.

Yes and no: The training can be quite grueling at times and you have to protect against fatigue and injury. You should try and get into a marathon training club and run and learn from others. I would also suggest cross training- possibly swimming and biking to help the muscles recover

Undecided: There are arguments on both sides. A marathoner for 36 years, I have my own opinion.Properly approached and with careful training,there are reports that it can be beneficial in many ways for longevity and overall health.Done improperly it can cause many problems and injuries. It is also dependent on the person and their overall health to start, systemic conditions, genetics, and mind set. Read up.

Not healthy.: Fitness can and should be achieved without a long list of extreme risks to health both short and long term. The balanced exercise and nutrition programs yield life changing results.