There's no definitive program to follow when it comes to losing weight. Some start off by making dietary changes while others hire personal trainers and begin working out three times a week. Regardless of what method you choose to lose weight, there's one very important fact you need to know about how weight-loss impacts your body.

Alex Caspero MA, RD, CLT, RYT, explained to POPSUGAR that "you often lose muscle mass when you lose weight, as it's almost impossible to just lose body fat." This may seem like a trivial fact, but losing muscle mass can result in your metabolism slowing down, which can interfere with your weight-loss goals. You may have heard that eating certain foods and drinking water in the morning [1] can boost your metabolism, but Alex said it has nothing to do with the foods you eat. The "secret" to a faster metabolism is exercise.

"The leaner body tissues (muscle) that you have in your body, the more you are able to burn calories without doing anything extra [2]," she said. Beware, though, because not all exercise is created equal. According to Alex, adding more muscle mass by lifting weights "can increase your resting metabolic rate [3] — how many calories you burn each day outside of activity." Instead of focusing on tons of cardio, maintain muscle mass by implementing weightlifting into your workout routine.

Give your metabolism a boost with this four-week beginner weightlifting program [4].