Overweight, Underweight, or Just Right

Tools to help determine your ideal weight.

You're working hard to lose weight. Every morning you work out and all day long you try to eat a healthy diet. And it's paying off. The scale is slowly moving in the right direction, your energy level is increasing, and your health is improving. You plan to make your new healthy habits stick, but how much longer must you focus on weight loss rather than weight maintenance? In other words, how can you know when you've reached your ideal weight?

Rather than comparing yourself to others, it's important to know the answer to this question is different for everyone. Your ideal weight involves at least three factors: your age, height, and sex. Other health experts believe the answer requires more details such as bone density, body fat percentage, or waist-to-hip ratio. Here's a look at the most common ways to determine your ideal weight.

Body Mass Index

Calculating your body mass index (BMI) is the simplest and most popular way to know if you're overweight, underweight, or just right. Your BMI looks at your weight in comparison to your height.

To find your BMI using metric units, take your weight (in kilograms) and divide that number by your height (in meters) squared. For example, the BMI for a person who weighs 100 kg and is 1.8 m tall is 30.86.

When using imperial units, the calculations are a little more complex. Take your weight (in pounds) and multiply it by 703. Then divide that number by your height (in inches) squared. A 200-pound person who's 6 feet (72 inches) tall has a BMI of 27.12. If math isn't your forte, you can easily find a BMI calculator online.

What do these numbers mean? A BMI under 18.5 is considered underweight, between 18.5 and 25 you're good to go, and over 25 you're obese.

Body Fat Percentage

Unfortunately, BMI is unable to account for other factors that influence health and weight. For example, it overestimates the amount of body fat in muscular or thin people and underestimates it in overweight people. Two people could be the same height or the same weight, but one is a marathon runner and the other sits around all day. Or, a large football player who's in great shape and is all muscle is categorized as obese. Remember, muscle weighs more than fat. Rather than using BMI to provide a picture of health, athletes may do better to calculate their body fat percentage to get an idea of how much of their total body weight is fat and how much is muscle, bone, skin, and organs.

Your doctor or personal trainer may use various methods (dual energy X-ray absorptiometry, near-infrared interactance, or bioelectrical impedance analysis) to determine body fat percentage, but none are perfect. The recommended amounts of body fat vary depending on your sex and fitness level, but anything over 25 percent is considered overweight for males and 31 percent or higher is considered overweight for females.

Waist-to-Hip Ratio

BMI calculations provide a general idea of a healthy weight compared to your height, but they overlook waist and hip circumferences, both of which affect health. If you carry extra weight around your middle and have an apple-shaped body, you're more at risk for cardiovascular health problems and type 2 diabetes as compared to people with pear-shaped bodies (excess weight around the hips and bottom).

Finding your waist-to-hip ratio is another method used to determine ideal body weight. First, measure the circumference of your waist, usually around your belly button. Second, measure the distance around your hips at the widest part. Then divide your waist measurement by your hip measurement. An answer of 1.0 or greater in men and a ratio of 0.85 or more in women is an indication that too much weight is being carried around the belly.