The gym membership expired, the self-help books are gathering dust, and the exercise DVDs now serve as coasters. If you’re still trying to make good on that New Year’s resolution to lose weight, the promise you’ve been making to yourself year after year, maybe it’s time to take a new approach. And chances are you’ve already got the tools you need to succeed. You’ve got a cell phone, don’t you?

That’s right. Motivation to lose weight has been tucked in your pocket or buried in your purse all this time. By utilizing social networks such as Facebook, you can tap into a network of friends who will help you stay on task to reach your goal.

“The best way is to have accountability (to reach your weight loss goals) by telling everyone you know,” said personal trainer Christian Aguirre. “So posting pictures on Facebook, your blog or YouTube channel to show your progress is a great way to peer pressure yourself to do well.”

The easiest way to spread this news with one click is to post it on Facebook or Twitter. By announcing your goal to the world, you’ve immediately got a group of people who are going to want updates on your progress, and by accessing the Facebook application on your phone, you can update your progress as it happens.

Some Facebook users are so dedicated to losing weight that they start their own fan pages so that their friends and family can directly track their progress. With regular posts and photo updates, people can see how you’re doing and encourage you to keep going.

U.C. San Diego professor James Fowler, co-author of “Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives,” said Facebook can play a huge role in the success or failure of weight-loss goals.

“You can’t do it alone,” Fowler said in a 2010 interview on “The Colbert Report.” “What you really need to do if you want to make a positive change is get your friends and family involved because they are going to have a strong influence on you. If you try to lose weight on your own and they’re not trying to lose weight as well, it’s going to be very hard for you to meet your goals.”

So when you’re standing in line at the grocery store, let people know that you’re stocking up on fruits and vegetables and didn’t even go down the snack aisle. Your friends will be proud of you. They might even follow your lead.

In a 2010 study at the University of Georgia, volunteers were divided into two groups. One group watched a person eat a cookie and the other group watched a person eat a carrot. When the test groups were presented with the option to eat a carrot or cookie, 71 percent of those who watched a person eat a cookie chose to snack on a cookie. Author Michelle vanDellen determined that self-control is influenced by the behaviors of those around us, so people tend to mimic what others are doing despite how they would typically respond to a situation.

By publicizing your goals to lose weight on Facebook, you are channeling peer pressure to your advantage and encouraging others to join your effort. There are groups you can join on Facebook to help keep you motivated, but if you have a group of friends who share the same goal, start up your own group and look for others in your area who also want to lose weight.

You can’t be the only person in East County who resolved to shed some pounds in 2011, so work together, support each other and make this the year that you finally meet your weight loss goals.