Is BMI 17.79 Underweight?
Yes, a BMI of 17.79 is classified as underweight and falls below the healthy weight range for adults.
BMI Classification Standards
According to established international guidelines, BMI categories are defined as follows:
- Underweight: BMI < 18.5 kg/m² 1, 2, 3
- Normal/Healthy weight: BMI 18.5-24.9 kg/m² 1, 2, 3
- Overweight: BMI 25.0-29.9 kg/m² 1, 2
- Obese: BMI ≥ 30.0 kg/m² 1, 2
Your BMI of 17.79 falls into the underweight category, as it is below the 18.5 kg/m² threshold. 1, 2
Health Implications of Being Underweight
Being underweight carries specific health risks that warrant clinical attention:
Increased mortality risk: Underweight individuals have been shown to have greater mortality in multiple studies, though the specific disease associations differ from those seen in obesity 4
Associated morbidities: Research demonstrates U-shaped relationships between BMI and various health conditions, with underweight individuals showing increased risk for respiratory disease, limitations in activities of daily living, and mental health issues 4
Demographic patterns: Underweight individuals are more likely to be younger, current smokers, alcohol abstainers, physically inactive, and of lower socioeconomic status 4
Specific disease associations: Among underweight smokers, there are elevated odds of cancer, bowel disorders, ulcers, and migraine 5
Clinical Assessment Recommendations
For someone with a BMI of 17.79, the following evaluation is warranted:
Assess for underlying causes: Investigate history of weight loss, dietary habits, chronic diseases, malabsorption syndromes, hyperthyroidism, malignancies, psychiatric conditions (eating disorders, depression), and medications that may suppress appetite 1
Evaluate for complications: Screen for nutritional deficiencies, bone density issues (osteoporosis risk), immune dysfunction, and reproductive health problems 4
Consider smoking status: The health risks associated with being underweight are modified by smoking status, with underweight smokers showing particularly elevated risks for certain conditions 5
Management Approach
The goal for individuals with BMI < 18.5 kg/m² should be to achieve a healthy weight in the normal range (BMI 18.5-24.9 kg/m²). 1, 3
Target weight gain: Work toward reaching at least BMI 18.5 kg/m² through increased caloric intake and addressing any underlying medical or psychiatric conditions 1
Monitor for complications: Regular assessment for the health risks associated with being underweight, particularly if weight continues to decline 4
Address modifiable risk factors: Smoking cessation is particularly important given the compounded health risks in underweight smokers 4, 5