What sort of activities are you doing for exercise and what does your diet look like in terms of calories/meal?
Are you eating the same quantities of food as you did when you were 15 pounds lighter?
FWIW, here's a brief story about ... ME!
When I was 45, I found I had ballooned up to 185 pounds from my ideal 170. My first step was to flip my meal sizes around. Bigger breakfast, about the same size lunch, dramatically less for dinner (more salads, less fat and protein portions). I actually did this more because I was having BG problems overnight, than the weight thing, but I found over 6 - 9 months that I had dropped some weight and improved my overnight BG numbers. Now don't misunderstand my method. I still have the occasional BIG DINNER, but no longer is it the everyday standard.
The second thing I did was look for opportunities to be more active. For me, I seem to have a direct correlation between activity and increased metabolism. (I even have two basal settings. One when I know I have been more sedentary, and the other for when I have been active.) I realized that being in an office environment was keeping me SITTING at my desk or in too many meetings. I began to always skip the elevator in favor of the stairs, walk outside for a break and after lunch and I started parking my car in the farthest corner of the parking lot. The result again was not only improved BG, but a few more pounds off. I happily hovered around 173 - 177 for a number of years before step 3.
Step 3 was going to the gym 2 - 3X/week and finding a group class that worked for me. I dropped as low as 160 but now I hover around 167 - 173.
One thing that also worked for me was to forget about the weight and just concentrate on eating a little differently, staying active and trying to improve my fitness. The weight loss was just an added benefit.
I have no scales in my house and only get on the scales in the gym every few weeks.