Lenders are being more conservative these days. As stated below in other comments your debt to income ratio must be high. It is possible that someone can make $100,000 but have more than 50% of their income go to bills, credit cards, loans, etc. That will limit your buying power. If you need a higher loan approval, I would look at your credit cards, bills, etc and see which ones you can attack to either eliminate or lower. Then you can have the lender re assess your buying power.
You could always get a second opinion from another lender. Maybe the first lender missed something.
All the best,
Coldwell Banker Star Realty
BRE Lic #01456982