Excuse-proof your workout - CNN.com Studies have shown that regular exercise can actually increase your energy level. We make excuses to reduce our discomfort about not doing something, expert says Getting into the exercise habit can lead to a "healthy obsession" Top excuses for not exercising include lack of time and lack of energy (Health.com) -- We all have our reasons for not working out. Some are legit -- we're working late or nursing an injury -- but often we're just talking ourselves out of exercising. "We make excuses to reduce what's called cognitive dissonance," says Dan Kirschenbaum, professor of psychiatry and behavioral sciences at Northwestern University Medical School. If we are committed to exercise and yet don't do it, the excuse allows us to feel less dissonance, or discomfort. That's not to say you're lazy; it's a normal response. The secret to countering it? Get into the habit of working out. When you do that, your brain flips a switch and develops a "healthy obsession," which makes you want to get moving, Kirschenbaum explains. Until then, here's how to overcome your top four gym deterrents (as revealed in a Health.com poll). No matter what your psyche throws at you, we have you covered. Health.com: 30-minute workout, no gym required The excuse: I'm too pooped. The reality: It's the number-one reason you blow off workouts. Know this, though: Studies have shown that regular physical activity can improve energy. If you don't believe it, commit to a week of exercise and see if you notice a difference. Of course, for many of us who work out in the morning, simply getting ourselves out of bed is the issue. If that's you, download the Sleep Cycle alarm clock app ($.99; iTunes). Then place your phone on an upper corner of your mattress and set the app's alarm for a 30-minute window; your iPhone's built-in accelerometer measures your subtle movements, and the app wakes you when you're in your lightest sleep phase, when you're most rested and ready to get active. Prefer working out at the end of the day (when your Circadian rhythms want you to chill)? Enlist an exercise buddy -- it'll make it harder to skip the gym. The excuse: There aren't enough hours in the day. The reality: You're busy, for sure. But the time is there, insists Laura Vanderkam, author of the book "168 Hours: You Have More Time Than You Think." "If you work 50 hours a week and sleep eight hours a night, that leaves 62 hours for other things," she says. And the American Heart Association says 75 minutes of vigorous exercise is all you need to squeeze in each week to improve your health. To find pockets of unused time, keep a 24-hour log of one weekday and one weekend day. You'll quickly see where you can slip in mini chunks of exercise. "Most people find they could take a 30-minute walk over their lunch hour," Vanderkam says. Health.com: Walk off 350 calories in 45 minutes The excuse: I don't want to redo my hair and makeup. The reality: You can take care of post-workout primping in five minutes flat with this regimen from Paige Padgett, green beauty expert and Jillian Michaels's makeup artist. Give your sweaty spots a once-over with an antibacterial wipe, and do the same on your face, using an all-in-one cleansing pad. Next, apply a beauty balm, which is similar to a tinted moisturizer, but with the added benefits of a primer and blemish control ointment. Touch up mascara and use a three-in-one color stick to add shimmer to eyes, cheeks, and lips. Finally, apply a little dry shampoo to the crown of your head to freshen up your hair, and you're done. Health.com: Beauty tips from Bobbi Brown The excuse: Exercise makes me eat more. The reality: Actually, if you work out at a moderate-to-vigorous level (think a brisk walk), a shift in hormones may help suppress your appetite immediately post-workout. In a recent study, researchers at Brigham Young University showed images of food to women who had just finished a 45-minute morning workout. Their neural response to the food was less than it was on non-exercise days. The researchers also found that women did not eat more on the workout day to make up for calories burned. The key? Eat a snack right after your workout, says Stella L. Volpe, chair of the department of nutrition sciences at Drexel University. Aim for a 150- to 200-calorie mix of protein, carbs, and healthy fats. It'll keep you feeling full so you don't eat back all those calories you just burned off.