Midlife is a time of transition, and many things will change, including your body. There are things you can do to help manage those changes and control your health as you age.

Here are three things to focus on:

Your Bones

It's easy to take your bones for granted even though they've been holding you up your entire life. At mid-life, they become more important than ever. After menopause, you have far less estrogen available to maintain bone. Hence, bone-destroying cells get the upper hand, putting you at risk for osteoporosis. What to do? Ask your health care professional about your personal risk for osteoporosis. While bone density screening tests aren't usually recommended until 65, some health-related issues warrant earlier screening. Regardless of your risk factors, the following two approaches can help you maintain existing bone and continue to build bone:

• High levels of calcium. You should be getting at least 1,200 milligrams a day, but most women get only about 600 milligrams through their diet, so supplements like calcium citrate and calcium carbonate might be necessary.
   
• Weight-bearing exercise. It's important that you get some weight-bearing exercise most days, like walking, gardening or working out with weights.

Your Heart

Your biggest risk after you pass menopause is not breast cancer but heart disease. It's the leading cause of death in women over 45. Unfortunately, not enough women realize this. So if you haven't already, now is the time to really start paying attention to things like cholesterol levels, weight, physical activity and diet.

Why now? Well, until now high levels of estrogen protected your heart, one reason women develop heart disease an average of 10 years later than men. However, as estrogen levels decline, so does that protection. While it's still not clear if supplemental estrogen can continue that protection, that's almost beside the point. If you're eating a heart-healthy diet composed of healthy fats, lots of fruits, vegetables and fiber, and low-fat protein like fish and soy, accompanied by at least 30 minutes of physical activity a day, you're well on your way to providing your body with what it needs to replace the previous protection of estrogen.

Oh yeah—and stop smoking. If you smoke, you're two to six times more likely to suffer a heart attack than a nonsmoking woman, and your risk increases with the number of cigarettes you smoke each day. You also have a significantly higher risk of heart disease if you have diabetes, high blood pressure or high cholesterol or if you are obese and/or have low levels of physical activity.

Your Blood Sugar

You can't feel it or taste it, but if your blood sugar levels start to creep up, you're putting yourself at increased risk for everything from heart and kidney disease to dementia, nerve damage and early death. You don't even have to be officially diagnosed with diabetes to find yourself in trouble. A condition called "insulin resistance," in which your cells prevent insulin from "unlocking" the door so energy in the form of glucose can enter, also increases your risk of heart disease, as does full-blown diabetes.

The remedy? Watch your diet, get regular physical activity and try to maintain a healthy weight—nothing new here. And if you're 45 and older, make sure you're getting regular blood sugar tests at least every three years. Your health care professional may want to test you more often depending on your risk factors for developing diabetes. Also measure your waist every few months. A high waist-to-hip ratio increases your risk of insulin resistance and diabetes.