Weight Change (Not Weight!) Is A Vital SignTuesday, August 15, 2017
Why do doctors weigh people? Because, very early in medical school, we are taught that body weight is an important indicator of health.
While one may certainly argue about the value of a single weight measurement at any point in time (especially in adults), there is simply no denying that weight trajectories (changes in body weight – up or down) can provide important (often vital) clinical information.
Let’s begin with the easiest (and least arguable) situations of all – unintentional weight loss.
Among all clinical parameters one could possibly measure, perhaps non should be as alarming as someone losing weight without actively trying. In almost every single instance of “unintentional” weight loss, the underlying problem needs to be found, and more often than not, the diagnosis is probably serious (cancer is just one possibility).
As with any serious condition, the earlier you detect it, the sooner you can do something about it, therefore, the more often you weight someone, the more likely you will detect early “non-intentional” weight loss.
The contrary situation (un-intentional weight gain) is as important. When someone is gaining weight for no good reason, one needs to look for the underlying cause, which can include everything from an endocrine problem to heart failure.
On the other hand, weight stability, is generally a sign that things are probably “under control”, as they should be when energy homeostasis works fine and people are in energy balance.
Perhaps my own obsession with weighing people comes from my work in nephrology, where we obsess about people’s “dry weight” and use weight as a general means to monitor fluid status. The same is true for working with patients who have heart failure.
Note for all of the above, that while a single (random) weight measurement tells you very little (almost nothing) about anybody’s health status, unexplained changes in body weight are one of the most useful and important clinical signs in all of medicine. Obviously, to plot a trajectory, one has to start somewhere, which means that every patient needs to have a “baseline” body weight recorded somewhere in their chart. While this value may not provide any valuable information, the next one may.
This is why every single patient needs to be weighed at least once in a clinical setting.
As you will imagine, both the context and interpretation of serial weight measurements becomes most challenging in the setting of obesity management.
For one, there is no greater challenge than to suspect underlying “un-intentional” weight loss in someone who is actively trying to lose weight. When “suddenly” a weight loss strategy that was providing modest results “starts working” – all alarm bells should go off. Also, if weight loss is much better than “predicted” it is time to take a serious second look at what’s happening. Furthermore, you need to watch out for patients who are doing far better than expected (even after bariatric surgery) – it takes a keen clinical mind to watch out for weight loss that appears “too good to be true” (even if the patient is delighted to see the pounds drop off).
Also, in the obesity management setting, weight stability is an important clinical indicator. In someone at their maximum weight, it tells me that the patient is not actively gaining weight, which by definition means that the patient is in caloric balance – remember, the first sign of “success” in obesity management is when the patient stops gaining weight.
In someone, who has already lost weight (in the context of obesity management), weight stability means that the patient’s efforts are continuing (here weight stability is a means to monitor “control”) – weight regain means that the patient may have to re-engage in weight control efforts or (more often) that something has come up in that person’s life that is “sabotaging” their efforts and may need to be identified and addressed (e.g. lost a job, change in medication, depression, etc.). Again, the earlier you identify a “relapse”, the earlier you can intervene.
Finally, in someone attending an obesity clinic, who continues gaining weight, you can be sure that the underlying cause of weight gain has not yet been fully identified or addressed. In other words, the disease is not “controlled” and continues to “progress”.
Thus, patients must be aware, that asking not to be weighed (usually out of shame or embarrassment) derives their clinician of important and possibly “vital” information about their health status.
Again, while a single weight (or BMI) says very little about a patient’s health, changes in body weight (up or down) is a vital sign that should prompt further clinical investigation and possibly intervention.
None of this has anything to do with the fact that people can very well be healthy over a wide range of body shapes and sizes.
It also does not mean that we should take a “weight-centric” approach to obesity management – all of the usual HAES arguments remain valid, even when you regularly ask your patient to step on the scale.
Recording a weight trajectory should be no more “judgemental” than recording a fever chart in a patient with an infection – everything lies in the context and interpretation of the data.