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Healthy Weight Center

Calculating BMI



My weight is 100lbs and my height is 5.6 ft am I under weight?


Body Mass Index (or BMI) is a ratio of your height and weight.  According to health experts and national health organizations, BMIs between 18.5 and 25 are associated with the greatest chance of health and lowest disease risk.  Persons with BMIs below 18.5 are considered to be underweight.  Low BMIs are associated with decreased immunities, which could lead to illnesses and conditions such as lack of menstrual periods, bone loss, malnutrition, and respiratory diseases. The lower your BMI, the greater these risks become. 

According to BMI tables, the healthiest weight range for someone of your height is between 115 and 155 pounds.  Your BMI is 16.1 and is considered underweight. First, you should consult with your physician to determine if you have any underlying physical causes for your low weight.  If your physician recommends weight gain, then you should eat frequent meals/snacks that include healthy foods and beverages.  Fruit smoothies, milkshakes, or commercial supplements (such as Boost) are often an easy way to consume extra calories and nutrients.  Try to eat foods that are packed with nutrients in addition to calories, such as dried fruits, nuts, peanut butter, juices, and low-fat cheese.  Also, you should engage in weight lifting/strength training exercises 3 times per week, so that you gain weight as muscle mass, rather than only body fat.  You should aim for a gradual, healthy weight gain of about 1/2 to 1 pound per week.  Good luck! 

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Response by:

Bonnie J Brehm, PhD, RD Bonnie J Brehm, PhD, RD
Professor of Nursing
College of Nursing
University of Cincinnati