I am 29 years old, and I fast regularly on Mondays and Thursdays. My father wants me to limit it to one day only, but I am able to cope with fasting. If I go against his wishes, am I being disobedient to him?
Praise be to Allah
If the situation is as you describe, then you are not being disobedient to your father by going against him when he tells you not to fast on both Monday and Thursday, because your fasting two days is an act of worship, so long as you are able to do that, and there is no obedience to any created being if it involves disobedience towards Allah. Moreover, what appears to be the case is that he is trying to be kind to you and is not forcing you not to fast.
And Allah is the source of strength. May Allah send blessings and peace upon our Prophet Mohammed and his family and companions. End quote.
And Allah knows best.