Body mass index, or BMI, is a classification system that uses weight and height to determine weight status in adults. Although many people associate BMI with obesity, it can also be used to classify severely underweight individuals. If you have a BMI that indicates that you are significantly underweight or overweight, your doctor may recommend further testing to determine if you are also malnourished.
Malnutrition
Lab Tests Online defines malnutrition as a disparity between the amount of food and nutrients you consume and the amount of nutrients your body actually needs. While most people associate malnutrition with undernutrition, or not eating enough, it can also be used to describe overnutrition, or eating too much.
BMI Classification
BMI values are divided into four main categories: underweight, normal weight, overweight and obese. A BMI of less than 18.50 indicates that you are underweight. The underweight category is further classified into three separate underweight categories. A BMI between 17.00 and 18.49 indicates mild thinness, while a BMI between 16.00 and 16.99 indicates moderate thinness. A BMI below 16.00 indicates severe thinness and is the classification most likely to accompany undernutrition.
If your BMI falls between25.00 and 25.99, it indicates that you are overweight. Once your BMI reaches 30.00, it indicates obesity. Obesity is further separated into three classes. A BMI of 30.00 to 34.99 falls into obese class I, while a BMI of 35.00 to 39.99 falls into obese class II. Obese class III, or a BMI of 40.00 or more, indicates morbid obesity. A BMI of 25.00 or more may accompany overnutrition.
BMI Calculation
You can calculate your BMI with two different formulas. With the metric system, you divide your weight in kilograms by your height in meters squared. If you are not familiar with kilograms and meters, the BMI calculations are also given in pounds and inches. To determine your BMI this way, divide your weight in pounds by your height in inches and then multiply the total by 703.
Considerations
While your BMI may be used as a screening tool for malnutrition, it is not a diagnostic tool. In order to determine if you are malnourished, your doctor may order several other diagnostic tests. Some tests used for general malnutrition screening include a complete blood count, a comprehensive metabolic panel, lipids, albumin and total protein. If your BMI indicates that you are underweight, your doctor may also recommend iron tests, prealbumin and various vitamin and mineral tests, including vitamin B-12, folate, vitamin D, calcium and magnesium.
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