Don't Thin Out Your Skeleton

If you lose too much weight or are naturally very thin, you could be at higher risk for osteoporosis.

Think of your bones as levers that help lift limbs. When these levers lift more weight, they become denser and more resistant to fracture. That's why a little meat on your " ones can help protect them, says Jane Kirby, R.D. Being too in is actually a risk factor for osteoporosis. There's more. Kirby says that when women shed too many pounds and body fat drops dramatically, menstruation ceases and blood estrogen levels plummet. The lack of estrogen imperils bones, because this hormone helps calcium get into your skeleton and stay there.

To find out where you stand, Kirby recommends taking our Body Mass Index (BMI). BMI compares weight to height o determine proper weight. Here's how.

1.Convert your height to inches.
2.Weigh yourself first thing in the morning, naked.
3.Multiply your weight in pounds by 704.5.
4.Divide #3 by your height in inches
5.Divide #4 by your height in inches again. That's your BMI.

Below 19 means you are too thin; 19 to 25 translates to a normal weight; 25 to 29.9 means you're overweight; you're obese if your BMI is 30 or above.

If you're underweight, you may need to cut back on exercise so you don't burn more calories than you consume— but enough that you still get the minimum weight-bearing, strength-training, and flexibility quotas described in Schedule Bone Benefiters into Your Day on page 41. You also need to eat more, being sure to choose a balanced diet.

—Jane Kirby, R.D., is a nutrition consultant in Charlotte, Vermont.