BMI Calculator for Amputee

The Body Mass Index, or BMI, is a measurement of a person’s height and weight. It is calculated by dividing a person’s weight in kilos by the square of his or her height in meters. BMI is currently the decisive parameter to determine whether you are underweight, normal weight, overweight, or obese, according to the National Institute of Health (NIH). As a result, knowing your BMI is critical to keeping a healthy physique and a high level of fitness. A healthy BMI can also aid in the prevention of ailments such as heart disease, type 2 diabetes, and hypertension. A normal BMI indicates that you are at your ideal weight. BMI is a quantitative assessment of an individual’s tissue mass, which includes muscles, fat, and bones.

If you’re an athlete or otherwise physically active, your body weight may be high due to muscle rather than fat. Muscle is denser than fat, therefore having more muscle implies carrying more weight and hence having a higher BMI. However, it is not unhealthy in this case because it does not carry the health hazards that a high BMI rating does.

Weight and height are used to calculate a person’s ideal body mass index (BMI). If a patient has had a limb amputated, the BMI must be adjusted to account for the missing limb. An amputee’s BMI can be calculated by adding a percentage to the person’s actual weight.

How is BMI calculated?

BMI is calculated using the following formula:

For pounds and inches:

  • BMI= [Weight (lb)/height (in)2] x 703

For kilograms and meters:

  • BMI= Weight (kg)/[height (m)]2

The usual BMI formula must be modified to account for the anticipated weight of the missing limb for patients with limb loss. People who have had limbs amputated can use the following formula to determine their BMI:

Calculation Process:

Step 1 – Calculate estimated body weight

  • We= W0/(1-P)

Step 2 – Calculate estimated BMI

  • Estimated BMI = [estimated body weight (lb)/height (in)2] x 703
  • Estimated BMI = [We(lb)/height(in)2] x 703

Keep in mind,

  • W0 = weight without the prosthetic device (lb)
  • P = percentage of total body weight of missing limb (lb)
  • We = estimated body weight (lb)

Estimates of the percentage of total body mass that can be atrophied at various amputation levels were used for P. Through a review of the literature and interactions with other scholars, these estimations were derived.

Amputation LevelEstimated Percentage of Total Body Mass
Foot1.30
Below-Knee3.26
Above-Knee9.96
Hemipelvectomy/
Hip Disarticulation
11.83
Shoulder Disarticulation5.00
Above-Elbow3.55
Below-Elbow1.45
Hand.70

How is BMI interpreted?

The following BMI ranges are used to categorize a person’s weight status:

BMIWeight Status
Below 18.5Underweight
18.5 – 24.9Normal
25.0 – 29.9Overweight
30.0 and AboveObese

Estimated Body Weight Loss (EBWL) Table

For estimating a patient’s amputation optimum body weight, the following figures are feasible (or adjusted body weight for overweight patients).

Level of Amputation% EBWL
Foot1.5%
Below-knee amputation (BKA)3.5%
Above-knee amputation (AKA)11%
Hip disarticulation16%
Hand0.7%
Forearm1.5%
Entire arm4%

Ideal and Adjusted Amputation Body Weight

The equation below is used to calculate an optimum body weight equation (as reported by Devine 1974) for patients without amputations. The EBWL is used to compute a percent of estimated ideal body weight for people who have had amputations:

  • Ideal BW(men)=50+2.3∗(height over 60 inches)
  • Ideal BW (women)=45.5+2.3∗(height over 60 inches)
  • Amputation ideal BW=(1−EBWL)∗Ideal BW

Adjusted body weight

An “amputation adjusted weight” may be utilized in patients who are more than 30% of their amputation ideal weight. The adjustment factor for this modified body weight is 0.4. (or 40 percent ). For calculations like creatinine clearance, adjusted body weight is typically utilized.

  • Adjusted BW=Ideal BW+(0.4∗(Actual BW−Ideal BW))

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