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Two Huge Novel Studies Farther Undermine The Obesity Paradox

The "obesity paradox" is the observation that people amongst higher fatty volume sometimes convey amend wellness outcomes than thin people, including a lower overall opportunity of death.  Evidence has been steadily mounting that this finding may live on a misleading artifact of the methods used to discover it.  Two massive novel studies add together to this evidence.

Despite the fact that excess trunk fatty contributes to the opportunity of a let on of mutual diseases, many observational studies convey reported that people inwards the overweight or fifty-fifty obese categories sometimes sense amend wellness outcomes than thin people.  This is the "obesity paradox".  I covered this concept inwards particular before this twelvemonth (1).

Yet equally amongst all observational methods, these findings are vulnerable to confounding-- too it tin sometimes live on profoundly misleading.  There are reasons to believe that confounding could live on peculiarly relevant here.  First, people who are sick tend to lose weight, making leanness await to a greater extent than unsafe than it actually is.  Second, cigarette smokers tend to live on leaner than nonsmokers, too likewise much less healthy, likewise making leanness await dangerous.

Fortunately, at that spot are ways to right for these potential confounding factors, at to the lowest degree to some degree.  The interrogation of Andrew Stokes has shown that when nosotros produce so, the obesity paradox goes away (1).  Two new studies strongly confirm that when confounding is minimized, at that spot is no paradox.

Study #1: "BMI too all displace mortality: systematic review too non-linear dose-response meta-analysis of 230 cohort studies amongst 3.74 million deaths amid 30.3 ane K k participants"

This is a huge meta-analysis which, equally the championship suggests, includes mortality statistics from a whopping 30.3 ane K k people of all weights (2).

The affair I actually similar well-nigh this study is that they analyzed several subsets of the data, each of which was progressively less probable to live on confounded.  If nosotros hypothesize that the obesity paradox is an illusion that results from confounding, thence each additional stride toward minimizing confounding should brand the paradox less apparent.

And that's precisely what happened.  In all subjects, equally good equally electrical flow smokers, the lowest mortality flat occurred at a trunk volume index (BMI) of 25, which is on the cusp of overweight.  Yet amid people who convey never smoked, the optimal BMI was 23-24.  Among people who had never smoked too who were good for you lot at baseline, the optimal BMI was 22-23.  And amid people who had never smoked too were followed upwardly for at to the lowest degree xx years, the optimal BMI was 20-22!  That is quite lean.

The concluding analysis is a peculiarly powerful way of avoiding confounding due to existing illness.  If you're recording a person's weight right at in ane lawsuit too their opportunity of expiry inwards xx years, it's probable that whatever kills them inwards xx years is non impacting their weight right now.  So you lot teach a cleaner assessment of the touching of BMI on health.  This assessment shows that it's much to a greater extent than unsafe to live on obese than to live on underweight.  You tin encounter that inwards this graph of BMI vs. mortality from the paper:

From figure 3. BMI is on the horizontal axis, too mortality charge per unit of measurement is on the vertical axis.  The horizontal white lines stand upwardly for relative opportunity of 1, 1.5, 2, too 3.  The give of the graph represents a relative opportunity of 5.
It is worth noting that at that spot isn't a lot of excess opportunity upwardly to a BMI of 25, too fifty-fifty into the lower overweight make (BMI 27).  It's actually inwards the obese make that the opportunity flat increases substantially.

Study #2: "Body-Mass Index inwards 2.3 Million Adolescents too Cardiovascular Death inwards Adulthood"

This is an Israeli study that, in ane lawsuit again equally the championship suggests, measured BMI inwards 2.3 ane K k adolescents too subsequent expiry rates inwards adulthood, amongst a particular focus on cardiovascular deaths (3).

Like the previous study, this ane is remarkable due to the extra-long follow-up flow betwixt BMI measuring too death: upwardly to 44 years, amongst a hateful of around 25 years!  This agency that at that spot was commonly a long flow of fourth dimension betwixt the BMI measuring too the expiry outcome.  This is compounded past times the fact that the researchers measured BMI inwards adolescents 16-19 years of age-- a fourth dimension at which real few people endure from overt disease.  Both of these factors minimize confounding.

When nosotros consider amount mortality, remarkably the healthiest BMI make was betwixt 19.7 too 21.4 inwards men, too betwixt 19.2 too 21.0 inwards women.  That is real lean, simply proceed inwards heed that it was measured inwards 16-19 year-olds, who tend to convey a naturally lower BMI.  That make was likewise optimal or nearly thence for most types of expiry reported, including stroke, abrupt death, amount cardiovascular deaths, too non-cardiovascular deaths.  The ane exception was coronary pump illness death, which was lowest at the lowest BMI (12-18! Not recommended).

This graph clearly illustrates the consistent human relationship betwixt adolescent BMI too subsequently cardiovascular mortality inwards this study:

On the vertical axis, nosotros convey cardiovascular mortality, too on the horizontal axis, the let on of years since BMI was measured.  Each business on the graph represents a unlike BMI category.  BMI is listed past times percentile rather than absolute values.  Lower percentiles stand upwardly for lower BMIs.

The longer the follow-up, the to a greater extent than apparent the BMI outcome became. Note that at the longest follow-up, cardiovascular mortality opportunity differed past times nearly 4-fold betwixt BMI extremes.  This is a huge effect.  Again, the opportunity is concentrated inwards the higher BMI categories.


Two huge novel studies amongst compelling designs add together substantial weight to the hypothesis that at that spot is no obesity paradox.  As suggested past times controlled studies inwards animals too humans, excess trunk fatness probable contributes to chronic illness opportunity too the overall opportunity of dying.  Risk increases inwards parallel amongst excess fat, silent BMI values at the upper destination of the thin range, too fifty-fifty into the lower overweight range, don't seem to live on especially unsafe (particularly amid people amongst higher thin mass)*.  Furthermore, good for you lot behaviors such equally physical action too a high-quality diet tin attenuate opportunity inwards people of all weights.

* People of Asian/Indian ancestry may live on an exception.  Their opportunity flat increases to a greater extent than sharply at a lower BMI level.


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