Nevertheless, epidemiologists (and folks in health promotion) appear to like the notion that there is such a weight (at least at the population level), and often define it as the weight (or rather BMI level) where people have the longest life-expectancy.
Readers of this literature may have noticed that the BMI level associated with the lowest mortality has been creeping up.
Case in point, a new study by Shoaib Afzal and colleagues from Denmark, published in JAMA, that looks at the relationship between BMI and mortality in three distinct populations based cohorts.
The cohorts are from the same general population enrolled at different times: the Copenhagen City Heart Study in 1976-1978 (n = 13 704) and 1991-1994 (n = 9482) and the Copenhagen General Population Study in 2003-2013 (n = 97 362). All participants were followed up to November 2014, emigration, or death, whichever came first.
The key finding of this study is that over the various studies, there was a 3.3 unit increase in BMI associated with the lowest mortality when comparing the 1976-1978 cohort with that recruited in 2003-2013.
Thus, The BMI value that was associated with the lowest all-cause mortality was 23.7 in the 1976-1978 cohort, 24.6 in the 1991-1994 cohort, and 27.0 in the 2003-2013 cohort.
Similarly, the corresponding BMI estimates for cardiovascular mortality were 23.2, 24.0, and 26.4, respectively, and for other mortality, 24.1, 26.8, and 27.8, respectively.
At a population level, these shifts are anything but spectacular!
After all, a 3.3 unit increase in BMI for someone who is 5’7″ (1.7 m) is just over 20 lbs (~10 Kg).
In plain language, this means that to have the same life expectancy today, of someone back in the late 70s, you’d actually have to be about 20 lbs heavier.
While I am sure that these data will be welcomed by those who would argue that the whole obesity epidemic thing is overrated, I think that the data are indeed interesting for another reason.
Namely, they should prompt speculation about why heavier people are living longer today than before.
There are two general possible explanations for this:
For one these changes may be the result of a general improvement in health status of Danes related to decreased smoking, increased physical activity or changes in social determinants of health (e.g. work hours).
On the other hand, as the authors argue, this secular trend may be that improved treatment for cardiovascular risk factors or complicating diseases, which has indeed reduced mortality in all weight classes, may have had even greater beneficial effects in people with a higher BMI. Thus, obese individuals may have had a higher selective decrease in mortality.
There is in fact no doubt that medical management of problems directly linked to obesity including diabetes, hypertension and dyslipidemia have dramatically improved over the past decades.
Thus, it appears that the notion of “healthy” weight is a shifting target and that changes in lifestyle and medical management may have more than compensated for an almost 20 lb weight increase in the population.
This is all the more reason that the current BMI cutoffs and weight-centric management of obesity both at a population and individual level may need to be revisited or at least tempered with measures of health that go beyond just numbers on the scale.
Regular readers are by now familiar with the Edmonton Obesity Staging System (EOSS), that classifies individuals with obesity based on its impact on physical, mental and functional health.
Now, Stasia Hadjiyannakis and colleagues present an adaptation of EOSS for kids, published in Pediatrics and Child Health.
The evidence-informed paediatric clinical obesity staging system (EOSS-P), builds on EOSS for adults and captures the severity of disease, as well as factors that complicate management, within four domains of health most commonly encountered in obesity:
The EOSS-P assesses four main domains that are impacted by obesity and can impact responsiveness to weight management – metabolic, mechanical, mental, milieu:
Metabolic complications of paediatric obesity include glucose dysregulation (including type 2 diabetes [T2D]), dyslipidemia, the metabolic syndrome, nonalcoholic fatty liver disease, hypertension and, in adolescent females, polycystic ovary syndrome. Metabolic complications are often asymptomatic and must be screened for to be identified. Screening should begin at two years of age for lipid disorders, three years of age for hypertension and at 10 years of age or at the onset of puberty, if this occurs earlier, for diabetes. Metabolic complications of obesity can improve significantly through changes in health behaviour with minimal change in BMI.
Biomechanical complications of paediatric obesity include sleep apnea, sleep disordered breathing, gastroesophageal reflux disease, and musculoskeletal pain and dysfunction. The presence of sleep apnea and/or sleep disordered breathing can exacerbate the metabolic complications of obesity, have deleterious neurobehavioural effects, and affect appetite and food intake. Biomechanical complications can be barriers to weight management and affect prognosis. If left inadequately treated, biomechanical complications of obesity can promote further weight gain.
Children and youth with obesity are at risk for social isolation and stigmatization. Childhood psychiatric disorders (eg, depression, anxiety), school difficulties, body dissatisfaction, dysregulated eating behaviours, teasing and bullying have all been linked to paediatric obesity. Children and youth with obesity have consistently reported lower health-related quality of life compared with normative samples. Mental health disorders, as well as some of the pharmacotherapeutic agents that are used to manage them, can complicate weight management, promote weight gain and affect prognosis.
An assessment of the family, school and neighbourhood milieus (the social milieu) is unique to the paediatric staging system and is important given the key role that parents, family members, schools and communities/neighbourhoods play in the health and wellbeing of children and youth. School difficulties and family factors, such as poor parental health, maternal depression, poor family functioning, receipt of social assistance, lack of emotional support, single parenthood and maternal drug use, have been associated with childhood obesity. Exposure to greater levels of psychosocial stress has been associated with higher levels of self-reported illness and negative health outcomes. Parental involvement and support are integral to successful paediatric obesity management.
The EOSS-P can be applied to children with obesity who are ≥2 years of age. The staging system is a tool reliant on clinician ratings, which are based on common clinical assessments including medical history, clinical examination and routine investigations. The EOSS-P is based on the presence and degree of the 4Ms with four stages of increasing health risk severity (0, 1, 2 and 3). The 4Ms are distinct categories, and progression in one of the categories does not necessarily coincide with a concomitant increase in the others. Individuals are assigned the highest stage in which they present with any metabolic, mechanical, mental health or social milieu risk factors.
As the authors note,
“This assessment tool can help support improved clinical and administrative decisions regarding the allocation of resources (ie, human, financial, time) for obesity management, and provide a platform for future research and clinical care designed to individualize therapeutic options.”
I have little doubt that clinicians will welcome this adaptation of EOSS for pediatric care as enthusiastically as they have welcomed the adult version of EOSS.
While the often impressive benefits of bariatric surgery on health and quality of life in younger patients with severe obesity are well documented, the safety and benefits of bariatric surgery in older patients remains largely unclear.
Now, a systematic review by my colleague Alexandra Chow from the University of Alberta, Edmonton, Canada, published in Obesity Surgery looks at outcomes in patients older than 65 years of age.
The review includes data from 8 studies (1835 patients) of roux-en-Y gastric bypass surgery, all of which were case series.
Overall mean excess weight loss was about 70%, which is only marginally less than generally seen in younger patients with this procedure.
Mean 30-day mortality was 0.14 % with a post-operative complication rate of around 20%, with wound infections being the most common (8 %) followed by cardiorespiratory complications (3 %).
Thus, it appears that bariatric surgery is reasonably safe and produces meaningful clinical outcomes in patients beyond 65 years of age.
Obviously, I would assume that these numbers are better than expected as centres (including ours) are rather selective about patients as they get older. Thus, these outcomes may not be applicable to every patient above the age of 65.
Nevertheless, it appears that for selected elderly patients, bariatric surgery may well be considered an effective treatment for severe obesity despite a reasonable measure of risk.
The GLP-1 analogue liraglutide (Saxenda), recently launched in North America for the treatment of obesity, has now also been shown to improve symptoms (apnea-hypopnea index – AHI) of obstructive sleep apnea (OSA).
This, according to a paper by Blackman and colleagues published in the International Journal of Obesity.
This 32-week randomized, double-blind trial was conducted in about 360 non-diabetic participants with obesity who had moderate (AHI 15-29.9 events/h) or severe (AHI ⩾30 events/h) OSA and were unwilling/unable to use continuous positive airway pressure therapy (CPAP).
After 32 weeks, the mean reduction in AHI was greater with liraglutide (3.0 mg) than with placebo (-12.2 vs -6.1 events/h).
This improvement in sleep apnea was largely explained by the greater mean percentage weight loss compared with placebo (-5.7 vs -1.6%).
Additional findings included a greater reductions in HbA1c and systolic blood pressure in the participants treated with liraglutide versus placebo.
Liraglutide was generally well tolerated with no unexpected adverse effects.
Thus, it appears that in addition to weight loss, treatment with liraglutide 3.0 mg results in clinically meaningful improvements in the severity of obstructive sleep apnea, an important issue that affects both the cardiometabolic risk and quality of life of so many individuals living with obesity.
Disclaimer: I have received honoraria as a consultant and speaker for Novo Nordisk, the maker of liraglutide
When adjustable gastric banding was first introduced as a treatment for severe obesity, it was touted not only as a surgically simple procedure (which it is) but also as having the advantage of being “reversible”.
Unfortunately, as many patients who have had bands implanted only to discover that they either did not work or created all kinds of other problems, “simply” removing the band was often anything but “simple”.
Moreover, as with any obesity treatment, removing the band (or in other words, stopping the treatment) virtually guarantees weight regain, leaving the patients often back to where they were (if not worse off) than before the operation.
In reality this means that when bands need to be removed, they often have to be followed by a more definitive procedure like a sleeve gastrectomy (SG) or a Roux-en-Y gastric bypass (RYGB) (the operations that should probably have been done in the first place).
The debate that continues to rage between surgeons, is whether or not it is safer to remove the band and do the more definitive operation within a single procedure or in two separate operations.
Now my colleague Jerry Dang from the University of Alberta, Edmonton, Canada, has published a systematic review and meta-analysis of the two approaches in Obesity Surgery.
According to their analysis of 11 studies that included 1370 patients, there was no difference in the rates of complications, morbidity, or mortality between one-step and two-step revisions for both RYGB and SG groups.
Thus, the authors conclude that both immediate or delayed revisional bariatric surgeries are reasonable and comparable options for band revisions.
Overall however, this should not distract from the fact that a band removal in itself can be a difficult operation with its own set of complications and given the number of bands that have to be removed, it may be best be recommended that preference be given to doing an SG or RYGB as the primary procedure.
Fortunately, this is indeed proving to be the practice at an increasing number of surgical centres.