Body Mass Index (BMI) | Medical Calculators | Pediatric Oncall (2024)

Body Mass Index is a measure of the ideal size of a person's body. BMI can be explained as a result of the overall amount of fat-free mass for the body type, which is inversely proportional to the total body weight.

BMI calculator estimates the Body Mass Index (BMI) based the bodily characteristics such as height, weight, age, gender, and region of residence. BMI is often used to gauge overall body fat percentage in order to eliminate health risks associated with overweight and obesity. Ideal body weight is expressed in pounds and inches to understand person’s health and fitness levels.In order to attain a proper BMI, one should avoid sugar, dairy, highly processed foods, salt and saturated fat.

Ideal Cholesterol level: 4.2mg/dl - 6.6mg/dl

Ideal Blood Pressure: 129 mmHg – 145 mmHg

Risks Associated With Being Overweight

Obesity is a well-recognized problem among adults. It may increase your risk for certain health problems and may be linked to certain mental, psychological, emotional and social problems. It is often associated with a variety of adverse health conditions, including diabetes, heart disorders, gout, osteoarthritis, cancer, sleep apnoea, fatty liver disease and kidney disease.

Overweight and obesity leads to many complications.The risks associated with being overweight include:

• High blood pressure and glucose levels
• High triglyceride levels in the bloodstream
• Low levels of HDL cholesterol (the “good” cholesterol) in the blood
• Developing gestational diabetes which leads to severe complications in pregnancy
• Developing preeclampsia during pregancy causes health problems for mother & baby

Risks Associated With Being Underweight

Being underweight puts people at highest risk of dying, same as in the case of being obese or overweight. Adults who fall under the category of being underweight with a BMI under 18.5 or less have a 1.8 times higher risk of dying than those with a "normal" BMI of 18.5 to 24.9. Everyone experiences weight loss, but only about 30% lose as much as they'd like over the course of the year. In fact, underweight people typically gain a little weight over the course of the year, and they are usually quite successful in keeping it off (at least for the first few months).

Being underweight is a matter of concern:

For Child:

If a child is not gaining weight, it is a matter of concern. This is because there is not much exposure to children yet they are unhealthy or malnutrition.Several reasons which prevent children from gaining weight are chronic diarrhea, chronic liver disease, cystic fibrosis, problems in digestive and gut system. In this case, it is not advisable to feed the children with high calorie foods or fats. Proteins, carbohydrates and food which contain rich source of vitamin are suggested. PediaSure provides a good, rich source of protein, vitamins and multi minerals for children up to 13 years of age.

The risks for a child include:

• Malnutrition, Vitamin Deficiencies or Anemia
• Osteoporosis from too little Vitamin D and Calcium Deficiency
• Decreased immune function levels
• Increased risk for complications from surgery, be it a minor or a major surgery
• Growth and Development issues in parts like Brain, Height, etc.

To avoid risks in the adulthood period, proper care of diet and health is an essential element of growth and development. The daily-recommended intake of vitamin D is 250 IU/day. Some foods which are suggested for children to consume on a daily basis include foods that contain vitamin D, wide variety of cheese, fatty fish, meat, eggs, and fortified milk products. It is not advisable to rely solely on supplements to meet your vitamin D needs, especially in the winter months.

For Women: Women with a BMI of less than 18.5 are counted under the category of being underweight. A woman is not only responsible for her own life but also for the new life that she gives. If a woman is underweight, she may face a lot of complications, one of them being amenorrhoea.The lower your BMI, the lower your risk of getting early menopause, stomach cancer, osteoporosis, infertility, bone fracture and ectopic pregnancy. In women over 45, obesity increases the risk of several common and more serious conditions such as diabetes, heart disease, stroke, heart attack, lung disease, sleep apnoea , back and joint pain, diabetes mellitus, cancer and allergies .

For Men: In males, adolescent growth and development of bodily parts stops or becomes slower when men are underweight.

Following are the disorders which can occur in men:

• Weight range is too low resulting in fast exposure to diseases
• Malnutrition
• Immune function
• Surgical complications
• Osteoporosis
• Infertility
• Developmental delays

Limitation Of Body Mass Index In Children

Limitation of body mass index in children is of major concern if the body mass index of infants below the age of 2 is less than 10 – same as tobacco. Limitations of body mass index for children depends on their weight and height. For example, among young children, excess weight can cause sudden death by obstruction of the heart (coronary artery disease). As the body mass index increases with age, the likelihood of death due to causes other than heart disease decreases. For example, a BMI above the 95th percentile for a child (19 kg/m2) increases the risk of certain cancers, such as leukemia (white blood cells) and ovarian cancer (cancer of the ovary).

The expected body mass index for children varies between 20–22.5 kg/m2 (3). This range, which is provided by the American Academy of Paediatrics for use with children in the US, was derived from 2 studies which found children with BMI of 22–23 kg/m2 were significantly more likely to have poor growth. The exact mean of BMI between these groups is uncertain because the larger of the 2 studies included children who had an increased BMI.

Children with a high BMI (BMI ≥ 30) are typically smaller in height than children with a low BMI (BMI < 18). Therefore, when interpreting BMI status for children of different weight groups, the basic BMI for children should be used. A 1 SD difference in BMI, i.e., an increase of 1.5 kg/m 2, would result in a difference of 7.5 mm.

Limitations Of Body Mass Index In Adolescents

Limitations of Body mass index in adolescents are the subject of much debate, discussion and research. This is because there is no clarity being drawn as to how to calculate a BMI which includes the dependency of other factors on body weight and height.

Limitations of Body mass index in adolescents is that the BMI at 18 years of age is very well correlated with the BMI at the age 10–12 years, which is about 0.98. BMI at 10–12 years of age is a better predictor of future BMI for adults. In line with these estimates, weight in middle age is significantly associated with waist circumference at age 18 years (r = 0.53, p<0.001). Some studies suggest that BMI is a better indicator of body fatness than skinfold thickness, but some studies which have the relationship between BMI and body fatness indicate that BMI is a weak indicator of body fatness in adolescents. Thus, it is the quality of the data on body fatness, not BMI, that is most important to examine results in relation to adolescent body weight growth, which makes BMI a limitation for adults. The relative contribution of sex and age to adolescent body fatness has also been an area of much contention, because it appears that sex hormones may be a more important determinant than age for determining a person’s height and weight. Many studies indicate that weight gain in boys is related to puberty onset, while weight gain in girls appears to be related to cycle length.

Limitations Of Body Mass Index In Adults

Limitations of Body mass index in adults is difficult to address and assess precisely. The BMI does not measure body fat content and is not always an indicator of lean mass or fat mass.It also does not take into account fat mass, muscle mass or bone size of an adult body but can be used to monitor weight loss or gain over a long period.Thus the main limitation of BMI in adults is that it can only be calculated using the level of fat in the body and not any other parameter. Studies on body fat distributions at different levels of body fatness in adults have shown that BIA method is reliable when measuring BMI in young adults, as long as the data points are used for comparison and a good report can be prepared from the analysis of the data.

Additionally, BMI can be dependent on gender, age and physical fitness. For example, normal weight and obese people may have different BMI. In general, people with higher BMI have a sedentary lifestyle and a high intake of energy-dense foods. However, it is not possible to determine fat-free mass (FFM), which is a marker of muscular strength using BMI. Therefore, the use of BMI alone to assess weight is not always a reliable measurement of body composition and may underestimate muscular strength.

Hence, overall Body Mass Index can be summed up as a great tool to calculate normative indexes but it does not take into account other bodily characteristics and hence is not used frequently for adults. In case of children, they do not have much issues and the only index of their body remains height and weight to gauge whether a child is healthy or unhealthy, thus BMI seems to be an apt way of calculation for them.

References

Garrow, J.S. & Webster, J., 1985. Quetelet’s index (W/H2) as a measure of fatness. Int. J. Obes., 9(2), pp.147–153.

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