Losing weight can be a little harder as we age, but there are medical reasons for inability to lose weight, as well. You might ask your doctor to do some simple blood tests to make sure your thyroid is functioning properly. Ask for Free T3, Free T4 and TSH. Don't settle for just TSH, which is what most doctors will think is sufficient.
Another thing that often, prevents weight loss is insulin resistance, which inability to use insulin properly. This is a forerunner to type II diabetes. Ask for hemoglobin A1c, along with fasting blood glucose.
There "are" other things, but those, along with diet and exercise are the main issues when it comes to weight loss.
If you can tell us what you've tried, we can help you further...