how about trying to reconnect to old clients who are on their own right now. A campaign for them to avoid the pitfalls of holiday eating and to get a head start into the new year may be an angle to pursue.
How about marketing and running a Fall fitness challenge?
Fall is the new New Year… You could also run a special with current clients for referrals–and give them a small discount on your services for the referrals.
Make connections in your community. Teach a class for free or offer a free session to some local groups (schools, PTA, small businesses, etc…) to get the word out.
Also, make fitness and health connections in your area, as they may eventually become a referral resource for you.
Hope some of these suggestions help you.