If you're relying solely on running for weight loss, you may be disappointed. Here's how to work out smarter to get the results you want.

"My body just can't lose weight." That's the first thing I heard when I picked up the phone. Sounding frustrated and hopeless on the other end of the line, my client Sarah continued. "If you knew how hard I've been working, you'd understand. You'd know I wasn't making excuses."

Sarah first contacted me after a friend of hers had successfully lost weight through my online coaching program just six months after having a baby. I asked her to keep an open mind and walk me through everything she'd been doing in terms of diet and exercise. The problem was immediately clear: Sarah was putting in effort, but the type of effort-specifically her over-reliance on running for weight loss-wasn't the best way to lose fat and get the results she wanted.

Once Sarah understood why her approach to cardio was holding her back, we adjusted her plan and the pounds starting coming off again (seven pounds in one month, to be exact.) So to make sure your cardio training isn't the reason you're not losing weight, here are five common mistakes, plus simple solutions to get back on track. (Here, more on running for weight loss, and other cardio myths that could be holding you back.)

Running for Weight Loss Mistake No. 1: Your Workout Is Always the Same

Your body is an amazing machine. It's designed for efficiency, meaning if you do the same thing over and over again, the process becomes easier. This applies to your running workouts too. Not only will they start to feel more effortless (even if you're still sweating and pumping your legs), but your metabolism learns and reacts so that fewer calories are burned with the same exercise output.

This is where traditional "steady state" running falls short on a long-term weight-loss plan. Research conducted at the University of Tampa found that doing steady state cardio-such as running on the treadmill for 45 minutes at a consistent pace that's not near maximal effort (think sprinting)-helps with weight loss…but only initially. Subjects lost a few pounds during the first week and then kaput! Nothing more. The reason? Within one week, their metabolism had adjusted and now didn't need to work as hard to burn off the fat.

One of the biggest problems with running at a steady, moderate-intensity pace, is that the calories you burn are limited to the time you spend sweating. So once your body adapts, the benefit is limited. That's why weight training is oftentimes viewed as better than "just" running for weight loss. Lifting weights impacts your metabolism by causing mini-micro tears that need to be repaired. That healing process requires energy, which means you're burning more calories-a process that can sometimes last for nearly two days after your training session.

To put it more simply: With cardio, you can slog away for 30 minutes at a lower intensity and burn 200 calories-or you can just eat 200 fewer calories per day. It's the same thing. With weight training (or as you'll soon find out-sprints), that's not the case. The calories you burn are not limited to what you do in the gym. So while a little variety might not seem like a big change to your routine, it will have a dramatic impact on transforming your body.

Running for Weight Loss Mistake No. 2: You Go Longer, But Not Faster

One of the most important variables with any type of exercise-cardio or other-is intensity. If you look at the average person who runs, they pick a pace that they can maintain for a long duration. Think about it: When you jump on a treadmill, elliptical, or bike, you're starting with the intent to be there for a while. Whether it's 30 minutes or an hour, your goal is to push at a pace you can sustain, work hard, feel tired, and then go home. While this is great for endurance, it's not so great for fat loss. (Because you know you're wondering: Which is better, the elliptical or treadmill?)

A study in the Journal of the American Medical Association followed the exercise habits of more than 34,000 women and concluded that it took about an hour a day of moderate exercise (walking at 3mph) to maintain weight. Notice, that's not weight loss. And three miles per hour is not very fast.

Now imagine if instead of arbitrarily picking an amount of time to exercise, you focused on pushing yourself to certain level of difficulty. If the 3.0 on a treadmill would be a "four" on a difficulty scale of one to 10, what would happen if you pushed yourself at an eight or nine for a shorter period of time?

There's no need to guess, I'll tell you: More fat loss. Researchers at the University of Western Ontario compared short but intense exercise to long, less-intense cardio. One group performed four to six 30-second "sprints" while the other group did cardio for 30 to 60 minutes. The results were nothing short of amazing. Despite exercising for a fraction of the time, those in the sprint category burned more than twice as much body fat. (This is all why HIIT training is so good for you-and for weight loss.)

That's because the process of sprinting causes similar internal changes to your body as those that occur during weight training. Your body needs to replenish it's ATP (energy), convert lactic acid that's produced during exercise into glucose, and restore your blood hormone levels after an intense workout. All of those processes mean your body works harder and burns more fat-both of which don't happen during steady-state aerobics. (That being said, you shouldn't sprint every time you do a running workout for weight loss. Read this guide to interval running workouts for a full how-to.)

Running for Weight Loss Mistake No. 3: You Focus Too Much On Calories Burned

One of the most common weight-loss mistakes is believing that the majority of the calories you burn results from exercise. This is a dangerous misunderstanding. Simply being alive-sleeping, standing, eating, thinking-requires a tremendous amount of energy. The number of calories you burn at the gym actually pales in comparison to normal functioning and your daily activities that are not exercise based. (More on that here: Do I Have to Run to Lose Weight?)

Does that mean there's no need to hit the gym? Of course not. Exercise has many health benefits, but the type of exercise you perform in the gym will influence how many calories you burn outside of it. Running will burn calories, but sprinting or lifting weights will result in more muscle. And the more muscle you have on your body, the more calories your body burns just functioning.

Running for Weight Loss Mistake No. 4: You Don't Try Other Forms of Cardio

Now that you know muscle is important to your overall weight-loss goals, it only makes sense that you would want to do the type of training that helps this happen in the least amount of time. So if you're a lover of slower, longer duration cardio (or LISS), I have some bad news: "Endurance" running and walking (longer duration, lower intensity) impairs strength and muscle growth, according to research in the Journal of Strength and Conditioning Research. What's more, even if you increase the intensity and run on an incline, cycling is still better for gaining muscle and burning fat, researchers found.

Again, the point here is not that "running doesn't work for weight loss" or that there aren't any benefits. (In fact, running has tons of benefits for your overall health.) However, if you're looking for the most efficient weight loss strategy and are short on time, you might be better served by cycling (preferably at a high intensity), rather than going for a long walk or relying on running for weight loss. (Related: You Don't Need Cardio to Lose Weight-But There's a Catch)

Running for Weight Loss Mistake No. 5: You Run Too Much (Yes, Too Much!)

This might sound crazy, but just hang with me: The number on the scale might not be changing because you're running too much. While this isn't a problem for the majority of people struggling to drop a few pounds, I've worked with more than a few people-and seen hundreds of other case studies-where fat loss has been stunted by doing too much.

Exercise is an indisputable component of a healthy life, but it still puts stress on your body. And the demands of that stress impact your hormones, which also control your ability to lose fat. More specifically, the hormone cortisol is released when you exercise. All cortisol is not bad (despite what late-night TV and supplement ads might have you believe), but chronic stress and chronic cortisol can lead to insulin resistance which forces you to store belly fat against your best-laid plans. Research published in the journal Hormone Research found that long-distance running-like that done in endurance runners-causes a sustained increase in cortisol. And this increase in cortisol for long period of times can lead to more inflammation, slower recovery, breaking down your muscle tissue, building up fat, and even harm your immune functioning. (Related: 9 Signs You Should Skip the Gym)

Just as bad, if you're suffering from too much stress-whether it's the result of exercises for too many hours or not recovering with the right nutrition-you can harm your thyroid and lower your metabolic rate, making weight loss more difficult.