Do overdraft charges affect loan approval?

I would need to see the full file. In general it throws a red flag. The big question to the underwriter will the client have enough money on hand to make the monthly mortgage payments.

When you turn in your bank statements, turn in a letter explaining why you had four overdrafts. If your Loan Officer doesn't tell you to do that, or help you write the letter, he/she isn't doing his/her job thoroughly. There's no need to ask this question if your Loan Officer explained to you that overdraft fees throw a red flag to the underwriter. That red flag can best be resolved by a signed statement from you explaining why those overdraft fees exist. Most of the time, it's because you experienced an explainable hardship. Underwriters can be sympathetic as long as it's not a monthly occurrence. You'll be fine as long as you are not habitually doing so.

Just give a good letter of explanation, make it good

How old are the overdrafts? If they are recent enough that they are on statements that you are turning in to underwriting you will need a very good explanation of why you had them and hope you don't get denied but if they are truly as old as you are saying hopefully they aren't going to show up. Do you have a good explanation or extenuating circumstance of why you had 4 overdrafts? Underwriters are human also but it can't be because you just decided to have a wild weekend and just throw money out the window and catch up later if you know what I mean.