Yet some exercise is still better than none.
The old adage "use it or lose it" is truer than ever. People who maintain a vigorously active lifestyle as they age gain less weight than people who exercise at more moderate levels, according to a first-of-its-kind study that tracked a large group of runners who kept the same exercise regimen as they grew older.
The study also found that maintaining exercise with age is particularly effective in preventing extreme weight gain, which is associated with high blood pressure, high cholesterol, diabetes, and other diseases.

The structure of the L and M subunits of the photosynthetic reaction center from Rhodobacter sphaeroides (based on PDB entry 1PCR). The protein is represented in purple, the cofactors are represented in red, blue, black and yellow. Credit: Professor Neal Woodbury, Biodesign Institute at ASU