Many people make fitness-related New Year's resolutions, only to see them fall by the wayside. It's why gyms are packed in January, but back to normal by April.

How can you keep the momentum going throughout the year to achieve your goal of better health and/or weight loss?

These five tips will help you stick to your New Year's fitness resolutions:

Make one change at a time

It's easy to start off the New Year full of energy and grand plans, but starting small will give you a greater chance of success, according to the Mayo Clinic. Instead of planning an unrealistic workout schedule, aim for three days a week. Rather than swearing off all your favorite unhealthy treats, vow to limit them to a day or two a week.

As you succeed with smaller steps, these habits will soon become a routine that you can build on as you add new goals.

In this May 25, 2016 photo, members of the running group “November Project” run up and down the stairs of the Lincoln Memorial, in Washington. Fitness buffs around the country are bringing the ‘take the stairs’ advice to a whole new level as noteworthy landmarks have become unlikely, yet popular new workout sites. (AP Photo/Andrew Harnik)
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Don't go it alone

CNN cites a study that showed social interaction makes people more likely to work out. Instead of going it alone, sign up for a fitness class, join a local running club, walk with a friend during lunch or hire a personal trainer. The social aspect will help keep you going, and you'll be less likely to bail on your plans to exercise.

Even if you don't have people to work out with, a virtual fitness community like those you can create with a FitBit can help you keep on track.

Make it fun

Exercise doesn't have to be drudgery, positive psychology researcher Michelle Gielan told WebMD. Find a way to get fit that also lets you have fun, such as a dance class or other type of exercise that makes you feel happy. If you don't dread it, you'll be more likely to keep going.

Keep a food diary

Losing weight is a popular New Year's resolution. While no one strategy works for everyone, a food diary can be a helpful part of your success. Otherwise, it's easy to underestimate just how much you're eating, forgetting about that vending machine candy bar at work or the snack you had while watching TV.

One study found that people who kept a food diary lost more pounds than people who didn't, according to Business Insider. Consistency was key, whether you keep a printed diary or use an app to help.

Don't be too hard on yourself

It's unrealistic to think that you'll be perfect as you strive to attain your exercise or healthy eating goals, the American Psychological Association says.

Accept that you're going to have some ups and downs, and realize that what's important is getting back on track. Otherwise, a missed workout or two can derail you for the rest of the year.