Good nutrition is important throughout life, but it takes on special significance through your later years.

"All the nutritional things that we need to be concerned about as younger adults are even more important as we get older," says Alice Lichtenstein, professor of nutrition at Tufts University.

That's because starting in middle age (40 to 65), the body begins losing about 1 percent of muscle per year. Fat replaces the lost muscle and metabolism slowly declines. Add to that the inactivity that often occurs with aging, and the bottom line is that you need to eat fewer calories – or risk expanding with age.

What makes it even trickier is that the requirements for essential vitamins and minerals stay the same, and a few increase, with age.

To help provide guidance for older adults, Dr. Lichtenstein and her colleagues at Tufts have crafted a modified food pyramid. While it is designed for those 70 and older, its messages are good for all ages and are meant to be used in conjunction with the U.S. Department of Agriculture's Food Pyramid (www.mypyramid.gov).

The foundation of the pyramid for older adults is physical activity. There's clear evidence that staying active delays moderate-to-severe physical changes that begin in middle age. But even for those who have been sedentary, the latest research suggests that it's never too late to start moving more.

The recommendations for older adults highlight so-called lifestyle exercises, from walking the stairs to doing yardwork and housecleaning.

For the special nutritional needs of advancing age, it's important to eat foods rich in calcium, potassium and vitamins D, E and K. Federal food surveys show that many older Americans fall short on these nutrients.

The pyramid for seniors also emphasizes eating plenty of low-fat and nonfat dairy products – as well as juice and cereal fortified with calcium. And the pyramid urges drinking plenty of fluids, especially water. Older adults have to consciously drink fluids, rather than just waiting to feel thirsty. Current recommendations from the Institute of Medicine are 12 cups per day (beverages and food) for women 70 and older; 16 cups for men the same age.