photo: ericmcgregor

Working out with weights is a key part of a successful fitness routine for either men or women. Lifting weights not only builds muscle, but also increases metabolism helping you burn fat faster and strengthens your bones which is particularly important as you age.

According to a recent Newsweek article, there are four common mistakes that people who are new to weightlifting make. Regardless of whether you're a fitness pro or just starting out, make sure to avoid these workout blunders:

1. Not eating well. Just because you're working out with weights doesn't mean you can start to scarf down the fatty foods. Combining a fat laden diet with squats and free weight exercises can actually make your butt look bigger. The workouts add to your muscle mass, which then just pushes the fat layer out, making you bulge. So keep on a low fat diet to take advantage of the boost in metabolism you'll get from weights.

2. Using too light a weight. Doing endless repetitions with a light weight will do nothing for your muscles. To build muscle you need to stimulate them which means using enough weight to experience muscle failure in under 12 reps.

3. Using too much weight. The flip side to not using enough weight is piling on too much. Trying to lift a weight that's too heavy for you is a great way to get injured and can actually get in the way of muscle growth. Your muscles should be exhausted at the 11th or 12th rep of an exercise. If you can blow through 12 reps easily, you need to add weight. If you can't get past 3 or 4 reps, take some weight off.

4. Bad form. As important as getting the amount of weight right is, it's even more important to maintain good form throughout the exercise. One common mistake: engaging your back when doing bicep curls. If you're doing this, you're not growing your arms. If in doubt, check with a personal trainer to make sure you have the right form for each exercise in your routine.

Once you get beyond these common mistakes you'll see your body respond to lifting weights by growing muscle and shedding fat.