The Lancet Commission on the diagnosis of obesity: a step forward or a step back?

It has been an very exciting and active couple of weeks following the publication of the Lancet Commission which proposed a new definition of obesity. It is time that I pipe in with my thoughts.

This 109 page document was authored by dozens of global obesity specialists, and first I want to say that I have great respect for the amount of work and dedication required to put this document together. I’m going to focus on key points, and only on adults, in this blog post.

First off, they propose a new definition of obesity which is not purely based on body mass index (BMI). They propose that the diagnosis of obesity can be made with one of the following 3 criteria:

At least one measure of body size and BMI
At least two measurements of body size, regardless of BMI
Direct body fat measurement, such as with a DEXA scan

There are three measurements of body size that can be used:

Waist circumference
Waist-to-hip ratio
Waist-to-height ratio

I love that these criteria move us beyond BMI as a sole assessment for excess body fat. BMI (which is a calculation based on weight and height) does not tell us anything about body composition (fat versus muscle), nor fat distribution (subcutaneous – under the skin, vs the more metabolically dangerous visceral fat centrally and around the organs). Remember that BMI, waist circumference, and waist-to-hip ratio should be assessed with ethnicity-specific criteria in mind, and the latter two also with sex-specific criteria. I don’t feel that the DEXA criteria is overly useful, as this is expensive and little used in clinical practice.

Once the diagnosis of obesity is made based on these criteria, the Lancet Commission then recommends that we further classify individuals as having either clinical obesity, or preclinical obesity.

They define clinical obesity as a chronic disease due to obesity alone, and characterized by signs and symptoms of ongoing organ dysfunction and/or reduced ability to conduct daily activities. They include 18 criteria, at least 1 of which has to be met for adults, to make a diagnosis of clinical obesity.

I have a lot of concerns about this diagnosis of clinical obesity. We know that there are over 200 health issues associated with obesity, so many health conditions associated with elevated weight are not included in this list of 18 criteria. A glaring omission, for example, is type 2 diabetes. We know that type 2 diabetes is closely related to obesity, with 90% of people with type 2 diabetes also having obesity. However, by the Lancet criteria, a person with type 2 diabetes and obesity would not be diagnosed with clinical obesity. Another major glaring error is the exclusion of mental health issues from this list. We know that many mental health issues are seen in direct association with obesity. Impairment of quality of life associated with elevated weight as determined by the patient is also not on this list. This list excludes some aspects of the person’s lived experience and the opportunity for the person themselves to identify whether their elevated weight is impairing their overall wellbeing.

When an adult with obesity does not meet one of the 18 health conditions to diagnose clinical obesity, the Lancet commission then suggests that they be given a label of preclinical obesity. The messaging in the document is that in most cases, people with preclinical obesity should be recommended lifestyle support as their treatment. I am extremely concerned about this messaging. Effectively advising people with elevated weight but who do not (yet) have any of those 18 health complications to simply go home and ‘eat less, move more’ goes against what we have been educating on for so long, that it is important to treat obesity early, rather than wait for complications to arise before treating. We know that lifestyle support is effective only for very few people. I am also concerned that this approach to preclinical obesity amplifies bias and stigma against these individuals with the messaging that they should be able to manage weight with lifestyle approaches alone.

Finally, I am very concerned about how insurance companies and payors are going to interpret these criteria. Will a person with obesity and type 2 diabetes be denied coverage for weight management medication or bariatric surgery because diabetes is not on the Lancet list? That is just one example of many. If payors/insurers follow this document and pay for treatments for people who fit these 18 criteria, they may then decline people who have other weight related health issues, and that’s not fair. While I can appreciate that no health system can afford to pay for weight management medication for everyone with obesity, it’s also not fair to deny a person who wants to proactively manage their health before developing weight-related health issues, and to suggest that they should wait for a health issue to arise before they can get access to treatment.

BOTTOM LINE: In my view, the Lancet commission is helping our world take a big step forward beyond using BMI as the sole assessment for excess body fat, and that’s great. However, the considerations for obesity related health complications is too narrow, and I cannot agree with the implications that we should wait until a person with elevated weight develops health complications before we consider effective treatments.

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