Want to wear out your walking shoes as fast as we do? (Dr. Mike goes through a pair every 12 weeks.) Determined to hit the sidewalk (or treadmill) regularly despite rain, sleet, bad hair days and mismatched tube socks? YOU can. Just lace up your sneaks and bust through these "buts": Excuse: "I've got a cold."

Bust it: Walk to avoid sniffles and sneezes.

Every step you take mobilizes immune-system warriors that patrol your nose, throat and lungs to take down invading cold/flu viruses. The benefit lasts for hours afterward-which may explain this new finding: People who exercise five or more days a week have 46 percent fewer colds than those who work out once a week or less. When active people do catch a cold, their symptoms (sneezing, congestion, coughing, dripping) are 41 percent less severe.

Insider tip: If you haven't left the couch recently, don't start training for a triathlon today. Exercising to the point of exhaustion can suppress your immunity. Your goal is to get fit, not sick. Start by getting a pedometer (get a good one) to see how many steps a day you take. Then add 250 steps daily until you're doing 10,000 steps every day.

Excuse: I want to lose weight before shaping up in public!

Bust it: Don't wait. Being fit can save your life, even if you're overweight.

Walk in the privacy of your own home (buy a walking video, do laps in the house, dust off that old treadmill). Or pull on workout clothes you feel OK about (sweat pants, generous tops) and hike the neighborhood when few people are around. Just do it, because the answer to that hotly debated exercise question "Can you be fit AND fat?" is a resounding yes. In a string of recent studies, overweight adults with good cardio fitness were less likely to die young than even normal-weight unfit folks. All it takes to tune up your heart and blood vessels? A brisk daily walk.

Insider tip: Not that we don't want you to lose excess pounds. Being fit at a healthy weight is even better than fit and fat. But if you first succeed at daily walking, you'll find that success breeds success. It'll make losing weight that much easier. And blasting body fat -- especially belly fat -- lowers your risk for heart attacks, strokes, diabetes and several kinds of cancer.

Excuse: My bum knee might flare up.

Bust it: The right moves keep knees healthy.

Sit and wait until your joints are jumpin'? No way. Keeping leg and torso muscles strong and flexible works way better than "take two pain relievers and rest." Exercise itself won't increase your risk of arthritis. In fact, a moderately paced walk or other low-impact activities (swimming, cycling) plus light-weight strength-training seems to keep the cushioning cartilage in your knee joints healthy.

Insider tip: If you suspect you're vulnerable to knee osteoarthritis, avoid high-impact workouts (jogging, step aerobics) and moves that involve lots of knee bends (lunges, squats). They're hard on cartilage.

Excuse: I'm pregnant!

Bust it: Gentle exercise can improve your health, and your baby's, too.

Just one in four pregnant women gets the 150 minutes of exercise a week that even your favorite Uncle (Sam) recommends. A good program can ease baby-on-board effects like backaches, constipation and sleep problems. Junior benefits, too: Exercising moms-to-be deliver babies with healthier birth weights, which lowers baby's risk for weight problems later on.

Insider tip: For a great workout plan to help you thrive during pregnancy, see our book "YOU: Having a Baby." Skip downhill skiing, scuba diving and bungee jumping!

Excuse: I'm too stressed out.

Bust it: Exercise cuts anxiety by 29 percent.

Tense? Why melt down, spend 20 minutes venting to your best friend or scarf down doughnuts when walking takes a big bite out of angst? Yep. In a huge recent analysis, people who got physical for just 30 minutes a day cut their anxiety by almost a third, even if they were dealing with severe mind-body stressors like cancer. Male, female, young, old, makes no difference: You'll feel better after a walk.

Insider tip: Stick with it. There's growing evidence that exercise stress-proofs your brain in a few weeks. Meanwhile, you'll burn calories -- and your BFF won't be tempted to not answer the next time your number shows up on caller ID.

The YOU Docs, Mehmet Oz and Mike Roizen, are authors of "YOU: On a Diet." Want more? See "The Dr. Oz Show" on TV (check local listings). To submit questions, visit RealAge.com.