Our society seems to be obsessed with beauty, physical appearance and the entire idea of perfection. It's no wonder people are going to great lengths to achieve the ideal body. People spend hours at the gym trying to drop pounds and sculpt shapely muscles while also devoting much time and effort into eating healthy in order to look good. But does all of that hard work pay off or do genetics determine what our bodies will look like?

You can't change certain aspects of your appearance that were predetermined by genetics (unless of course you undergo painful plastic surgery). For example, your bone structure, frame size, the areas in which you tend to store extra fat, and your metabolism (to a certain extent) are determined by your DNA. So while you may hate that you have your mother's hips or your grandmother's thighs, these things are likely out of your control.

People often try unsuccessfully to "spot-reduce"--trying to tone and lose fat over just a specific area. Unfortunately you can't work out just your lower body to make your thighs shrink if this is your so-called trouble area. In order to improve muscle tone to the point that you notice visible results, you need to lose body fat that is layered on top of the muscle. It is impossible to cause fat to be lost in a targeted area as fat mass will be lost from your entire body in many areas as you create a calorie deficit from a combination of healthy eating and exercise. While you can't change your body shape or bone structure, you can certainly enlarge and strengthen your muscles while also losing fat mass on top of your muscles through a combination of exercise and decreased caloric intake. Things you can change include your weight, your muscle mass, and your body fat percentage. No matter how many lunges you do, you cannot change the shape of a muscle, you can only increase or decrease its size through exercise, or lack of exercise.

Also, you could be at a healthy body weight for your height but could still have an unfavorable body fat percentage, and this can affect the way your body looks even though you may not be overweight. Furthermore, if your muscle to fat ratio is not within the recommended percentages, you could be at risk for certain diseases. The World Health Organization and National Institutes of Health have charts for body fat percentage recommendations based on age and gender. Body fat percentage is something that can be changed by increasing muscle mass and decreasing fat mass through physical activity, including weight-bearing exercise.

The take home message: Exercise, while it can improve your outer appearance to a certain degree, should be done to improve overall health. Exercise strengthens muscles and connective tissues, which reduces your risk of injury. It also builds strong bones and helps maintain muscle mass that is naturally lost as we age. Focus on how exercise (along with healthy eating) makes you feel good.