There are a lot of ways to tell if you need to lose weight. Tou can climb on a scale, measure your waist circumference, or calculate your BMI or, body mass index. Dr. Karen Cooper, an obesity expert at Cleveland Clinic, says although BMI is not fool proof, it helps determine how much body fat you have.

"It gives you an idea of where you should be in terms of your weight. You know, studies have shown the higher your body mass index is, the more at risk you are for certain diseases," Cooper said.

BMI  is a measurement of how much body fat someone has. It's calculated by a formula that uses a person's weight and height. You're considered to be overweight if your BMI is 25 to 29.9. People with a BMI of 30 or more are obese.

A high BMI, coupled with a high waist measurement and/or other risk factors like high cholesterol, high blood pressure and family history of heart problems, indicates a need to lose weight. That's why Cooper says it's important to have your BMI checked regularly.  

"Every time you go to your doctor's office your body mass index should be recorded, but certainly once per year," said Cooper.

The BMI scale is for adults and separate measurements are used for children and teenagers, if necessary.