Determining an "ideal" weight is a complex process that considers various factors including body composition, gender, age, height, muscle mass, and health goals. Below is an explanation of some methods commonly used to determine ideal weight.
One of the most common methods used to determine if someone has a healthy weight is the Body Mass Index (BMI). This measure relates a person's weight to their height. Although it can be a useful initial approximation, it doesn't account for the ratio of fat to muscle mass. Thus, it can sometimes be misleading. For instance, an athlete with a lot of muscle mass might have a BMI that's classified as "overweight", even if they're actually quite fit and healthy.
Another measure considered is the waist-hip ratio. This is the circumference of the waist divided by the circumference of the hips. This measurement is used to take into account where body fat is stored. People with "apple-shaped" bodies (more fat around the waist) are at a higher risk for certain health issues than those with "pear-shaped" bodies (more fat around the hips).
A much more direct measure of body fat is the body fat percentage. This is the percentage of total body weight that is made up of fat. It can be measured with various methods, including skinfold measurements, bio-electrical impedance, and DEXA scans. Each gender and age group has a different "ideal" body fat percentage.
An individual's "ideal" weight can also vary depending on their health goals, how they feel at different weights, and their individual body structure. For instance, someone who does strength training might have a higher "ideal" weight than someone focusing on endurance.
In general, it's important to remember that an individual's ideal weight isn't a single number, but rather a range that reflects overall health and well-being. A health or fitness professional can help determine your personal ideal weight.