According to the Pew Research Center, nearly half of all American adults have smartphones. And for many of those users, their phone is everything: a personal planner, a photo album, a music library and a GPS, among many others. Why not let it manage your health too?

"Management guru Peter Drucker said something like: 'What gets measured gets done,' and that's true for fitness apps," says Fred Green, health and wellness coach at the Mayo Clinic's Dan Abraham Healthy Living Center in Rochester, Minn. "If you can connect behavioral change to results, it tends to motivate people to keep going."

He has seen many of his clients embrace the new technology and finds that those who are mobile-savvy tend to find apps more convenient than a traditional food or exercise journal. "It's also really eye-opening for some people."

He says that research on the effectiveness of health apps is still new, but the field shows promise.

Sarah Krieger, a registered dietician and spokesperson for the Academy of Nutrition and Dietetics, says that research shows that recording diet choices is critical for long-term success, explaining: "It makes you more accountable for what and how much you're eating."

She considers apps powerful, easy-to-use tools for this but warns that cheating - say, underreporting your portion size or adding an extra mile to your workout tally - is a common pitfall.

"You get out of it what you put into it," she says. "It won't lose weight for you."

While there's no magical app that can do this yet, there are still some useful ones out there. And better yet: They're free. Check out the following apps to get you on the right track. (Remember to check with your doctor or fitness professional before beginning any new routine.)

OVERALL WEIGHT LOSS

Lose It! by FitNow

- Features: Developed as a "big picture" look at your diet and exercise habits, Lose It! is perfect for those who have a specific goal in mind. And this app gives you what you need to achieve it in a healthy way. Say you want to lose one pound a week. You set your goal, and the app provides the steps - a daily "budget" of calories and activity - to achieve it.

- Available on: iPhone and Android

DIET

Calorie Counter by CalorieCount.com /About, Inc.

- Features: This app covers everything you need to monitor your calorie intake. It has an easy-to-use dashboard that offers a variety of graphs to track your progress. The food database is extensive, with a library over 100,000 foods and a barcode scanner for packaged foods.

- Available on: iPhone and Android

EXERCISE

MapMyFitness by MapMyFitness

- Features: Covering over 600 types of activities, the MapMyFitness app lets you track everything from running to cycling. It's GPS-enabled and allows you to see and record real-time stats about your workouts. It can sync with a variety of sensors (such as heart rate and speed) to give you a full picture of your performance. You can even set a voice prompt for hands-free updates.

- Available on: iPhone, Android and Blackberry

SLEEP

Sleep Time by Azumio

- Features: Getting a full night's sleep but still feeling tired in the morning? You may be waking up at the wrong time in your sleep cycle. And according to this app's developer, Sleep Time can track your sleep (based on your phone's accelerometer, which senses any movement) and wake you up during your lightest sleep phase. It also includes a white noise feature to help you fall asleep and offers a detailed analysis of your sleep quality each week.

- Available on: iPhone and Android

RELAXATION

Naturespace by Holographic Audio Theater

- Features: Good health isn't possible without a little relaxation. And while there's irony in using technology to commune with nature, the Naturespace app gets as close as possible if you're stuck indoors. "Like dreaming while awake," according to the developers, it really does transport the listener to a much-less stressful place.

- Available on: iPhone

• Read more articles by SHELBY SHEEHAN-BERNARD

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