What’s BMI?

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One of my RDNs posed this question Lately related to BMI levels for older adults:

I’ve been seeing transfer notes in the hospital along with other nursing homes with diet/nutrition histories where RDNs are charting that BMIs of less than 23 is underweight. By way of example, 1 note documented that a BMI of 21.3 was underweight”for age” for a guy who was 92. State surveyors are also requesting a list of residents with BMI under 21 and wanting to see interventions on them. The MDS doesn’t trigger for a low BMI until under 19. Do we need to adapt our practices?

The National Institute of Health classification of overweight and obesity by body mass index (BMI) is as follows:

Classification – Normal

Obesity Class – None

BMI (kg/m2) – 18.4-24.9

Classification – Overweight

Classification – Obesity

Obesity Class – I

BMI (kg/m2) – 30.0-34.9

Classification – Obesity

BMI (kg/m2) – 35.0-39.9

Obesity Class – III

BMI (kg/m2) – > 40

BMI is translated based on age, health history, usual body weight, and weight history.

Adults should be evaluated for indicators of nutritional status and decline using body mass index (BMI) as one of many factors. Data suggests that a higher BMI range could be protective in older adults and that the criteria for ideal weight (BMI of 18.5 to 25) may be too restrictive in the elderly. A lower BMI may be considered detrimental to older adults because of association with declining nutrition status, potential pressure ulcers, infection and other complications. A BMI of 19 or less may indicate nutritional depletion, while a BMI of 30 or above indicates obesity.

In the literature, there is a whole lot of conversation about a BMI of 21-23 (rather than 18/19) as considered on the low side for older adults. At the exact same time, there is a whole lot of conversation about the”obesity paradox” saying a higher BMI may be protective against some diseases and death. There is still a lot of controversy regarding the efficacy of BMI for older adults, irrespective of what is considered”too low” or”too high”.

To our knowledge, there are no firm recommendations from any source on BMI cutoffs for elderly adults. The MDS triggers a CAA if BMI is < 18.5, although as stated above a higher BMI are likely to be considered too low for older adults.

In clinical practice, the BMI number isn’t as important as how it compares to an individual’s history. Monitoring changes over time is what is important.

If state surveyors question if everyone with a low BMI requires an intervention, consider explaining that if a low BMI was normal with this person’s life history, then we would not attempt to correct it – although interventions might be put in place for other reasons (poor intake, weight loss, wounds, etc.). And for an older person with a high BMI of 35 who had been overweight their whole life, it is highly likely that habits and lifestyle are put and weight loss would likely not be necessary or successful at older age.

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