Estrogen and progesterone levels decrease significantly during menopause. Emotional and mental changes occur as well. The reduction of female hormones leads to redistribution of body fat, particularly to the abdominal area. Genes and hormones determine where we store fat, so we can't lose it selectively in one area. As we age, our bodies lose muscle and gain fat. Our nutritional needs change as well.
It is good that you are eating healthy and exercising, even if you are not able to fully reach your goal of flattening your stomach. The average woman needs about 100 fewer daily calories at age 40 that at age 20. Sometimes even when we eat the right foods, we may not be eating the correct amounts of food or portions. Start with controlling your portion sizes. Make sure to eat lean protein at every meal. The protein will keep your energy level up and satisfy your hunger for longer. Do not skip meals. Eat regularly so that your blood sugar does not spike and dip.
Make sure that your work out is a balance of cardio and weight training. Exercise is the only way to increase your metabolic rate. Many women have found that core strengthening exercises, such as Pilates, also helps them feel stronger and better.
Although you may not achieve your dream figure, your healthy lifestyle provides many other worthwhile benefits in terms of well being and longevity. Keep it up!