Getty Gym
Image source: Getty Images.

Your physical health is one of the best investments you can make. Taking the time and energy to stay fit can save you substantial healthcare costs down the line. Regular exercise increases longevity and reduces the risk for cardiovascular disease. It's also been shown to reduce stress, obesity, and high blood pressure. Plus, it makes you look good!

The first step most people take when they decide to focus on their fitness is to join a gym. Gyms are convenient, they have all the tools you need to get in shape, and they force you to put some money on the line -- which can be a key motivator for some. With the average gym membership floating around $60 per month -- $720 per year -- it's a substantial monetary investment.

Is that gym membership really worth the money, though?

It's not really about the money

It'll take more than paying for a gym membership to get in shape. You'll also have to invest your time and energy. If you're lacking in either, that monthly membership bill is a complete waste.

Over two-thirds of all gym memberships go unused. That's part of the business model big health clubs like Planet Fitness (NYSE:PLNT) rely on. With over 8.7 million members, Planet Fitness averages over 7,000 members per location. But there's almost no way 7,000 people will show up to a Planet Fitness on any day no matter how much pizza they have available for members. (Also, don't get me started on the irony of serving pizza at a gym.)

Still, many people keep their monthly gym memberships. For most, all it does is serve as a reminder of how little they used it last month and a false promise to get back in shape next month.

OK, so you actually go to the gym

If you invest the time and energy to get in shape, or you're pretty sure you won't stop going after a couple of months, there's one more key to making sure a gym membership is worth the money.

Your gym must suit your needs.

If you plan to mostly use low-impact cardio machines, a place like Planet Fitness, with its low monthly membership fee, might work for you. If you want to lift some heavy iron, though, Planet Fitness definitely won't cut it. There's no squat rack, and they'll kick you out if you try to deadlift!

Gettyimages Treadmills
Image source: Getty Images.

Find a good gym in your area, and ask for a free trial. Most gyms offer at least a week for free, so you can find out if it has everything you need. Once you've found a good gym, go find one or two more. That way you can comparison shop instead of just settling for "good enough" and whatever price they give you. Plus, more free weeks!

Do you even need a gym?

If you're truly committed to getting fit, you might even want to forego a gym membership. Sure a gym is nice and has lots of equipment and maybe some extra perks, but if you mostly use the treadmill or elliptical, you might be better off in the long run buying a nice one for yourself and setting it up in the basement.

A good treadmill costs less than $2,000 (three years of average gym membership costs), and you can probably buy a lightly used one or less fancy model for less. For the one-time cost, you'll have unlimited access to the treadmill (no more waiting for other members) and no excuses not to use it. If it ever turns into a clothes rack, you can sell it for whatever residual value remains.

Alternatively, you could buy a bike and start running more of your errands on two wheels. That's an option I just took, and even in the middle of winter in the midwest, I'm managing to go out a couple times a week for small grocery runs, various errands, and trips to the coffee shop. (My bike runs on caffeine.)

Heavy lifters should be able to get a power rack, barbell, weight plates, and flooring for less than a couple grand (three years of the average gym membership). That's the top-of-the line equipment, too, that you'd find in the best gyms. Also, don't underestimate what can be done with bodyweight exercises like pull-ups and push-ups.

Gettyimages Deadlift
Image source: Getty Images.

Space may be a limitation for some. You probably can't fit a lap pool in your house, and your landlord might not like you dropping heavy weights on your floor if you're renting, in which case a gym membership makes more sense. But if you're truly committed, which you should be, and you have room for the equipment that fits your needs in your house (or garage) consider a one-time investment and dropping the gym membership.

Most people spend money on a gym membership they either don't use or don't need. Don't be one of those people.

Adam Levy has no position in any stocks mentioned. The Motley Fool recommends Planet Fitness. The Motley Fool has a disclosure policy.