First of all, try to remember that an over 40 metabolism is a little slower to react than a younger person's. This means things will happen a bit slower for you. Not only will it take longer to loose the weight but you'll notice that your weight doesn't fluctuate back and forth as quickly either. Look for a healthy lifestyle instead of a weight loss program and you'll find your ideal weight as well as be healthier.
Finding your ideal weight is a personal journey. By the time you've reached 40 years of age you know whether you are happy at a certain weight. It may be 10lbs over or under the established weight for your body frame, or it can be even more. You and your doctor should discuss the ideal weight for you and how you can maintain that weight with a healthy lifestyle.
If you are not at the weight you would like to be, and you're exercising regularly and your doctor says your healthy, perhaps a bit of acceptance is in order.
Just as with any other weight loss program, consider the fact that you are over 40, that your metabolism has probably slowed down and that the best weight loss program may just be eating right, getting plenty of exercise through a favorite hobby, and getting plenty of sleep in order to maintain your personal weight.