But what if you've got a deadline? Say, four weeks? Or just in time for your Christmas party? Or New Year's?

Drew Starley, who runs a 28-day challenge at his Sydney fitness studio F45 CBD, says a lot can be done in four weeks. Here's how to get the most out of your program.

1. Have a goal

Even over the silly season, you should set yourself a fitness goal.

"They don't have to be crazy or overly ambitious, but something as simple as training two to three times a week, and maintaining a healthy diet to counter all the 'socialising' plus getting enough rest is a good place to start," says Starley.

"If you really want to make changes over four weeks, you'll have to put in some hard work. We recommend upping your training four to five sessions a week at fairly high intensity for 45 minutes."

2. Share your goals

Actually telling someone that you want to lose weight or get fit or be able to run up a hill, works, because you are less likely to give up if other people are supporting you and helping you succeed.

"If you've got your own little support team, they'll be there to give you that extra motivation when you need it."

3. Incremental improvement, generate big results

We've all been fooled by ads and headlines with fads that promise to drop a dress size by the weekend.

One of the biggest developmental milestones in adult life is acknowledging that your body is not a balloon. You can't blow it up and deflate it at will.

A four week challenge is a great motivator and it will certainly help at this time of year to avoid the many temptations that come in the form of food at parties, boozing and a kebab on the way home after a party … you get the general idea, but it will take some time before you reach your goal.

"We often have new members expect radical results overnight," says Starley.

"We love their enthusiasm, however we prefer to educate them about proper technique, building up their fitness levels, guiding them on what healthy eating, and the importance of active recovery/ sleep. All of this will lead to longer lasting results."

4. Get back on the wagon

So you're on your challenge but you've gone out and couldn't resist the entire bread basket. Then you thought, "I've stuffed it now, I might as well order the mornay. And the chocolate pudding. And the salted caramel tart. Just because." (Don't you love how because is a good enough reason after a bottle of wine?).

This one night might be enough to stop you continuing on your challenge, but the key is to get up the next morning and push through.

"We all experience setbacks, which can lead us back to bad habits," says Starley, "but if you're on a challenge, finish the challenge – that's the hard bit. It hasn't been all for nothing if you've had one off night. Continue to participate, share your results with the rest of the community in your challenge, get back on track! You'll be proud of yourself."

5. Routine is key

Just like babies, adults thrive on routine. It's much easier to create an exercise habit if you lock in times to work out. Habits take three weeks to establish, so with a four week challenge you should be very at home in your routine.

"Even better, book your classes online so that it's in your diary as an appointment," says Starley. "You're less likely to miss it if you make time for it, as though it's a business meeting."

6. Shock your system

The body likes to be challenged. Signing up for a four week intense exercise program then, can only be a good thing, especially if it involves mixing different exercises together.

7. Don't be embarrassed

"Too often we have members saying they're not fit enough or worried about how they look," says Starley.

"The thing is, nobody is looking at you – they're all focused on themselves! Completing a challenge is a huge confidence booster and even if you fall off the wagon a few times, it will set you up to succeed in the next one. The key is to keep going."

- juicedaily.com.au