The ability to calculate weight change for dietitians is essential. In this post, we talk about what to look for, how to use that information, and resources to help you get even better.
How to calculate weight change for dietitians
Understanding weight status for dietitians
One of the most essential skills in clinical nutrition is being able to calculate weight change as a dietitian.
Knowing how weight status impacts your patient’s overall health is often going to be a significant factor in identifying and evaluating the most acute nutritional issue as well as being able to write clear nutrition assessments.
Let’s start by thinking a little about what you should think about when looking at weight change in a clinical nutrition setting.
Three ways weight can change
Weight change will typically fall into one of three categories.
#1: Significant weight gain:
Weight gain might (or might not) be related to obesity or excessive energy intake.
#2: Significant weight loss
Weight loss might (or might not) be related to malnutrition or sarcopenia.
#3: Generally considered stable weight change
This is usually in the +/-10% of current weight range. Stable weight might (or might not) be related to being generally healthy or eating adequately.
Because so much of what you do as a registered dietitian in a clinical setting is based on professional judgment and the assessment of each individual patient, it’s so important to be able to think about each of these as more than a simply pre-assigned calculation.
Let’s talk about each one.
Introduction to significant weight change
We consider weight change to be significant when a patient’s weight either increases or decreases by a specific range over a specific amount of time. More specifically, weight change is determined when it’s either unintentional or unplanned and significant.
When calculating weight changes for dietitians, these ranges include:
- 5% x 1 month
- 7.5% x 3 months
- 10% x 6 months
These percentages are often associated with weight evaluation in long-term care settings. But they’re also applicable in acute care where they’re used to determine both weight gain and weight loss.
Weight change tips to remember
First, when you see unintentional weight change, BMI is not the primary factor identifying if that weight change is significant or not.
You must know what your patient’s UBW (usual body weight) was and what their CBW (current body weight) is in order to understand what that means for that individual person.
Why? Because significant weight change doesn’t immediately mean malnutrition.
You can have either significant weight gain or significant weight loss. You might see significant weight loss in someone who’s achieved a healthier weight status. Or significant weight gain where someone remains malnourished.
REMEMBER: Just because someone has a normal BMI does not mean they’re weight change should not be fully evaluated.
Second, always evaluate for malnutrition with significant weight change.
This might be easy-to-see malnutrition that shows up in the form of cachexia. Or it might present as malnutrition on a micronutrient level in an overweight patient who’s had significant weight loss but remains obese.
The opposite is also true. You might have a patient who’s had significant weight gain but remains significantly underweight. This doesn’t make their weight gain any less beneficial or worthy of mention in your assessment.
BOTTOM LINE: When it comes to weight status, never assume.
BMI will never tell a complete story.
For example, an Olympic athlete might have an elevated BMI because of their muscle mass and height.
A visual evaluation doesn’t tell the whole story either.
Think about someone who appears underweight but reports having a stable UBW for the last 45 years and you see they have a very healthy appetite, eating everything you offer them.
When it comes to evaluating weight status, always go through all the motions – from calculating weight change to the nutrition focused physical exam to talking with your patient. And do this all before making a final call about their weight status and their estimated nutritional needs.
Which brings us to possible reasons for weight change.
Reasons for weight change
Weight change can happen for a lot of different reasons. Here are two big ones:
- Medications (ex: steroids can increase weight, diuretics can decreased weight)
- Medical conditions (ex: edema, dysphagia, dementia, HD, anorexia)
And let’s not forget that there are two types of weight changes:
- Intentional weight change (anything that your patient meant to happen)
- Unintentional weight change (anything your patient did not mean to happen)
Knowing the cause of weight change is just as important as knowing that significant weight change has happened.
Why?
Because that reason can tell you a lot about your patient’s needs, what their overall health status might be, and what (if any) high risk issues they might struggle with.
Intentional vs Unintentional weight change
Most of the time you’re going to be paying closest attention to the unintentional weight changes you see happening with your patients.
But there will be times when someone has pushed their body to a place that’s resulted in a significant (and possibly unhealthy) weight change that’s worthy of discussion in your assessment.
This might happen with health challenges like:
- Disordered eating (both restrictive and excessive)
- Orthorexia
- Overexercising
All of these can lead to significant and even detrimental changes in weight status, while also being fully intentional decisions by the person making them.
You might even see that same person achieving a BMI that appears within normal limits (WNL), making your job that much harder.
The point here is to not make assumptions about weight status based on looks, BMI, or anything else other than a full assessment. For dietitians, calculating weight change must be an intentional activity.
Don’t assume there’s an intake issue before you consider all possibilities. Then confirm your assumption by talking to your patient, if you can.
Always justify your recommendations with evidence you can identify and back up with concrete and verifiable information.
Weight change Calculation
The calculation for weight change is straight forward and can be done using either pounds (lb) or kilograms (kg).
It looks like this:
UBW – CBW = amount of weight change
This is the UBW (usual body weight) subtracted from the CBW (current body weight) giving you the weight change. This might be a gain or a loss, depending on if the UBW is bigger or smaller than the CBW.
When you have the amount of weight your patient has changed, divide that by the UBW.
Weight change / UBW = percentage of weight change
If your UBW is bigger than the CBW, your patient has lost weight. If the CBW is bigger than the UBW, they’ve lost weight.
Either way, the calculation for determining the percentage of weight change is the same.
Resources for malnutrition screenings and NFPE support
For a long time, the justification for if someone was malnourished hinged heavily on BMI.
Now, it’s a much more comprehensive evaluation using both the malnutrition screening tool and often, the nutrition-focused physical exam.
Here are a few resources to help better support you in being able to justify pushing for a malnutrition diagnoses from a patient’s doctor or the facility you work in.
The Malnutrition Universal Screening Tool (MUST) is one of the most commonly used and simplest tools available to use in the health community. It’s already part of most EMRs and you’re likely to find this criteria for malnutrition embedded in your nutrition assessment template. But if you’re ever curious, it’s going to be the same almost everywhere you go.
Check it out again here in the NIH malnutrition screening and assessment resource.
Looking to justify your recommendation for a malnutrition diagnosis to a doctor? This AND position paper for the use of MST is a great place to start.
Resources to start doing better NFPE
Here are some quick resources for doing the nutrition focused physical exam (NFPE).
Check out what the NIH uses to teach NFPE to med students.
Today’s Dietitian has a NFPE case study to check out.
Nestle (the company that makes Boost brand oral nutritional supplements) has a couple good videos on their YouTube Education channel.
Part 1 is here.
Part 2 is here.
And That’s It!
Of course, this just scratches the surface and there’s a whole lot more we could talk about.
To get started with more practical ways to use this information, check out the Clinical Case Study Library. There’s a new case study coming out every month, or you can watch all the replays with monthly access to our live sessions.
For more support in writing the actual assessment and translating weight status into your documentation, check out the Clinical Evaluation Power Pack. This will set you up with everything you need to write clear, concise, and complete nutrition assessment summaries.
Or get it all and more in Clinical Bootcamp. This self-paced online course has a monthly live Q+A session to make sure you have all your questions answered and a full understanding of everything you need to be a great clinical dietitian.
If you feel like you’ve got to start one place, make it the Acute Care Starter Guide. You’ll get your feet wet with a solid roadmap to clinical nutrition — and you can move forward with everything on this list as you need it.
Want even more to help in clinical?
Check out The Nutrition Cheat Sheets Shop for all the nutrition education and clinical resources that will make your life easier.
