The clue to that is how much do you eat. Once you start tracking you will discover that PORTION control is the key along with exercise.
When we were younger we moved faster we ate faster too. now we eat more than we used to. Now we do not burn as many calories.
Doing your classes will be great but not choosing the right foods in the right portions it just will not go.
I can say all this I am 69 years old and over three years I have changed what I eat and I move more and enjoy life more. I have also lost 50 pounds and gone fro 22 to size 16 that are now loose again. Way to go.