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.
Managing weight in patients with type 2 diabetes (most of who have significant overweight or obesity) is always challenging, not least because many medications used to treat diabetes can also promote weight gain.
Now, a paper by Judy Shiau and colleagues from the University of Ottawa, in a paper published in the Canadian Journal of Diabetes, present the results of a retrospective cohort study (1992 to 2009) of weight, glycemic control and diabetes medications changes in 317 patients with obesity and type 2 diabetes at 6 months on a low-calorie diet program.
The program (week 1 to week 26) included mandatory weekly group sessions led by a dietitian, behaviour therapist or exercise therapist. All patients received OPTIFAST ®900 as full meal replacements (MR) starting at week 2. Patients consume 4 MR shakes per day for a total of 900 kcal per day, a regimen that is high in proteins (90g/day) and moderate in carbohydrates (67 g/day). Patients with initial body mass indexes (BMIs) of 33 kg/m2 or higher commited to 12 weeks of full MRs, while patients with initial BMIs below 33 started with 6 weeks of full MRs and the option to increase to up to 12 weeks of full MRs. Once patients completed their full MR regimen, there was a 5-week transition period to regular food, typically followed by a maintenance diet, as determined in a one-on- one dietitian counselling session.
As glycemic control improved with weight loss, anti-diabetes medications were adjusted or discontinued, thereby stopping any weight-gain-promoting medications first.
As the authors note,
“At 6 months, both groups had lost 16% of their weight, and the decreases or discontinuations of medications were 92% sulfonureas, 87% insulins, 79% thiazolidinediones, 78% alpha-glucosidase inhibitors, 50% meglitinides, 33% dipeptidyl peptidase-4 (DPP-4) inhibitors and 33% metformin. At 6 months, compared with baseline, A1C levels improved significantly and at 6 months, 30% of patients were no longer taking diabetes medications and had significantly better percentages of weight loss compared with those taking medications (18.6% vs. 16%; p=0.002).”
Thus, this paper shows that, a low-calorie meal replacement program can substantially improve glycemic control and reduce the need for anti-diabetes medications.
Unfortunately, as participants were transitioned to community care at 6 months, little is know about how long these effects last.
Nevertheless, with the increasing availability and use of weight-neutral or even weight-reducing anti-diabetes medications, one may expect that some of these effects can be sustained for relevant periods of time.
Last week I was an invited plenary speaker at the 1st International Diabetes Expert Conclave (IDEC2017) held in Pune, India.
This 3-day event, organised by Drs. Neeta Deshpande (Belgaum), Sanjay Agrawal (Pune) and colleagues, brought together well over 900 physicians from across India for a jam-packed program that covered everything from diabetic food disease and neuropathy to the latest in insulin pumps and devices – all in a uniquely Indian context.
I, of course, was there to speak on obesity, which featured prominently in the program. Topics on obesity ranged from the potential role of gut bugs to bariatric surgery. While Dr. Allison Goldfine, former Director of Clinical Research at the Joslin Diabetes Center in Boston spoke on the latest developments in anti-obesity pharmacotherapy (delivering her talk via Skype), I spoke about obesity as a chronic disease and the need to redefine obesity based on actual indicators of health rather than BMI.
During my visit in Pune, I also had the opportunity to visit with my friend and colleague Dr. Shashank Shah, whose bariatric surgical center in Pune alone performs about 75 to 100 bariatric operations per month – a remarkable number by any standards.
Of course, the overwhelming number of talks were given by Indian faculty (there being only a handful of select invited international faculty at the meeting), and I did come away most impressed by the breadth and depth of knowledge presented by the local speakers.
Diabetes care certainly appears to be in good hands although the sheer number of patients with diabetes (estimated at about 70 million, which I assume to be a rather conservative assessment), would provide a challenge to any health care system.
On the obesity front, things are a lot less rosy, given that (as everywhere else) obesity has yet to receive the same level of professional attention and expertise afforded to diabetes or other chronic diseases.
Thanks again to the organisers for inviting me to this exciting meeting and congratulations on an excellent event that bodes well for the 2nd Conclave planned for 2018.
The fifth item on the disease definition modification checklist developed by the Guidelines International Network (G-I-N) Preventing Overdiagnosis Working Group published in JAMA Internal Medicine, deals with issue of precision, accuracy, and reproducibility.
Obviously, any definition of obesity that requires clinical assessment and clinical judgement will not have the precision, accuracy, or reproducibility of simply measuring height and weight.
Thus, if we define obesity as the presence of abnormal or excess body fat that impairs health, we will necessarily have to deal with the issue of assessing health, which is not something that you can simply measure by stepping on a scale.
Rather, because abnormal or excess fat can affect virtually every organ system as well as psycho-social well-being, we are going to be faced with a rather complex system of diagnosing who has obesity and who hasn’t.
In fact, as the authors of the checklist point out,
“…an appropriate gold standard will rarely be available and therefore, traditional measures of diagnostic test accuracy, such as sensitivity and specificity, will generally not be appropriate.”
Both repeatability (agreement in identical conditions) as well as reproducibility (agreement across comparable conditions) may result from biological variability, analytical variability, and clinical judgement.
The only way to test the reproducibility and precision will be to evaluate the use of the new definition in clinical practice and ultimately determining whether or not clinicians can reasonably agree on who has the condition and who doesn’t.
While this may seem daunting to non-clinicians, let us remember that in clinical practice many diagnoses are dependent on clinical evaluations and clinical judgement, whereby experienced clinicians or specialists may perform better than the novice or the non-specialist (a good example is psychiatry, but there are countless other examples).
Moreover, there will always be grey areas in “borderline” cases, where examiners may disagree on the exact result and only time will tell, who is right.
Welcome to the messy world of clinical practice.
Just because BMI is simpler, more precisely measured, and more reproducible, does not make it a better measure of diagnosing whether or not someone actually has a disease.
After all it only makes sense that it will take a complex definition to diagnose a complex disease.
The third item on the disease definition modification checklist developed by the Guidelines International Network (G-I-N) Preventing Overdiagnosis Working Group published in JAMA Internal Medicine, pertains to the issue of why modify the disease definition at all?
With obesity being increasingly recognize as a chronic disease, it should be evident to anyone, that the current BMI-based definition of obesity, although simple (or rather simplistic), would label a substantial number of individuals as “diseased”, who may be in rather good health and, therefore, very unlikely to benefit from any obesity treatments (overdiagnosis).
On the other hand, the current BMI-based definition excludes a vast number of people, who may very well have health impairments attributable to abnormal or excess body fat, and may thus benefit from obesity treatments (underdiagnosis).
Although there have been many suggestions for replacing BMI with other anthropometric measures (e.g. waist-to-hip ratio, ponderal index, abdominal sagittal diameter, etc.), none of these measures would guarantee that the individuals identified by such measures, would indeed have health impairments attributable to abnormal or excess weight – their sensitivity and specificity, although perhaps marginally better than BMI in identifying individuals with excess body fat, would still not pass the sniff-test for a reliable diagnostic test of an actual disease.
In fact, given the diversity and heterogeneous nature of adipose tissue, even more precise measures of actual body composition (including sophisticated imaging techniques) would still not be enough to determine whether or not body fat in a given is in fact impairing health and warrants obesity treatment.
In contrast, a definition of obesity that requires the actual demonstration of health impairments (likely) attributable to abnormal or excess body fat, via a clinical assessment, would ensure that obesity is only diagnosed in individuals, who actually have a health problem and would therefore likely benefit from obesity treatments. This may well include individuals below the current BMI cut-off.
Thus, continuing to use BMI (or any other anthropometric measure or more sophisticated estimate of body fat) is simply not an option if we are serious about calling obesity a disease.