The Duchess, who lost her mother and grandmother to the condition, admitted to feeling "quite naughty" about her own lack of exercise.
She is now considering taking up pilates or even some Tai Chi.
"I did do a bit of yoga and used to do a lot of walking before I got married but I have let things slide," the Telegraph quoted her, as saying
"I thought I was doing enough to protect myself from osteoporosis but it seems not. I think I am going to have to make it my New Year's resolution - maybe to do some pilates or even some Tai Chi," she added.
Pilates, is a programme of simple bodily exercises to build up key muscles, while Tai Chi is a Chinese "soft" martial art.
Susie Dinan-Young of the University College London's Medical School, who drew up the exercise regime, said that the Duchess was surprised at the difficulty of the move.
"When the Duchess was watching the class she said to me 'this is so gentle', I said no and she asked me to show her what I meant so I gave her a rubber sheet and she realised the exercise was quite tough," she said.