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Weighing less than is normal, healthy, or required.
Insufficiency of weight.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

Obesity Task Force classification

Bariatric medicine A weight classification based on the body-mass index–BMI, per intl consensus. See Obesity.
Weight type–OTF classification  
Underweight  BMI ≤ 18.5
Normal  BMI 18.5–24.9
Overweight  BMI 25–29.9
Obese  BMI 25–29.9
 Class I   BMI 30–34.9
 Class II   BMI 35–39.9
 Class III   BMI ≥ 40
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


A ratio of height-to-waist circumference that is below an acceptable range for healthy people.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

Patient discussion about underweight

Q. I need food guide for underweight. This is Liam. I had three kids and all are underweight? I don’t know how to make them healthy. I need food guide for underweight. They refuse to have healthy food. How can I get him to eat more and eat healthy, without having to force them?

A. Liam, do not give them too much of juice as it often contain more sugar and less vitamins than fresh or frozen fruits. After a period, give them healthy drink (like milk) instead of juice. If your child is more active than the food they had, then the child will surely be termed as an underweight. So make sure to give, more energizing foods like carbohydrates for an over active kid.

Q. How to loss weight like a diet with tea,pills or other kind of healthy thing.

A. drink 8 oz of warm water with 1 tablespoon of lemon... first thing in the morning

More discussions about underweight
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References in periodicals archive ?
For the new analysis, researchers tracked 3,719 patients: 29% were underweight, 44% had normal weight, 11% were overweight, and 16% were obese.
Again, underweight patients had the highest risk of 28-day mortality (15%), compared with healthy weight (7%), overweight (4%), and obese patients (5%) (P = .003).
Underweight (OR, 1.76; 95% CI, 1.39-2.23) and morbidly obese patients (OR, 3.87; 95% CI, 3.06-4.89) had higher risks of having an ASA of 3 or more when presenting for surgery (Table 4).
At the same time, being underweight can be addressed at any point of a child's life through proper nutrition and a balanced diet.
Meanwhile, other parts of the West Midlands saw rates of underweight babies that were even higher than in Birmingham.
We assessed weight perception with one question, "How do you describe your body weight?" Response options included underweight, slightly underweight, normal, slightly overweight, and overweight.
"Underweight, anemic and malnourished children under the age of five should be taken care of.
Findings suggest underweight It was one of a series looking into the causes of chronic disease in women.
The authors say that if post-2000 trends continue, global levels of child and adolescent obesity will surpass those for moderately and severely underweight youth from the same age group by 2022.
Keano was taken to a vet who confirmed he had a chronic skin condition, was underweight and had an ear infection; and that the extent of his problems were causing him to suffer unnecessarily.
He was so underweight that the vet said if he'd been left another 24 hours, he would be dead.
Using the WHO growth chart, underweight (<2 S.D) children were designated as cases and those who are in normal weight for age were designated as controls.