Conversely, if you cut calories too much, you may lose some weight initially, which makes you think you're doing the right thing. But that can backfire, according to Rachel Myers, trainer at Onelife Fitness Atlanta's Alpharetta location.
"A lot of people, if they're trying to lose weight, will really cut their calories too much. This puts your body into what's called starvation mode, and it tries to hold onto your fat," she said. Myers said that 1,600 calories a day is the absolute lowest anyone should be getting.
2. You're building muscle.
Running doesn't create a lot of bulk, but it does allow you to slowly build muscle, especially in your lower body. Since muscle weighs more than fat, you may not see the scale budge, or you could actually put on a few pounds. This is especially true if you were close to your ideal weight when you started running.
Instead of focusing solely on the scale, pay attention to your specific body measurements, how your clothes fit, your energy level, your endurance and – most importantly – how your overall fitness and well-being has increased.
3. You're not burning as many calories as you think.
Running is an excellent form of exercise, and it can greatly increase your overall cardiovascular fitness. It may not burn as many calories as you think, however. A 140-pound woman who runs for 30 minutes at 6 miles per hour (the equivalent of a 10-minute mile) will burn an estimated 318 calories, according to WebMD's exercise calculator. That's about the number of calories that are in a plain, medium-sized bagel with 1 tablespoon of low-fat cream cheese. You'll need to have at least a 3,500 calorie deficit between what you burn and what you take in to lose a pound of weight, and some experts think that in actual practice it takes a lot more than 3,500.
And if you rely on heart rate monitors that come on many treadmills, you may falsely believe that you're burning more calories than you really are, Myers said. She said that when she uses a heart rate monitor on her own (preferably one that straps across her chest), she finds that she's burning about 30 percent fewer calories than treadmill monitors usually report. Runners can also mistakenly believe they're keeping a steady pace and going faster than they really are. Myers said that she sometimes doesn't realize her pace has fallen until she looks at her heart rate monitor.
4. You need to vary your routine.
People who exercise a good bit can reach a weight loss plateau. Experts recommend varying your activities to produce an increase in the number of calories you burn. For example, if you're a runner, you could also bike or swim. In addition, adding some strength training into your workout can help you build more muscle, which helps speed up your metabolism.
"A lot of people do too much cardio and not enough weights. The more muscle you have, the more fat you burn, no matter what you're doing," Myers said.
She also recommended varying your routine by doing intervals. Try alternating between running fast for a minute and walking for a minute. These short bursts can help burn calories more quickly and raise your metabolism.
If you're running but not losing weight, take a look at your specific numbers, from body measurements to your heart rate. You may need to vary your routine and change your eating habits to lose the weight you want.