We read the recent article by Lavie et al. (1) and found it to be yet another in a long list of publications inciting unnecessary confusion about the effects of obesity. First, the authors describe the well-known consequences of obesity, for example, cardiovascular disease (CVD). Then the confusion begins. They cite 13 of their own articles, stating; “in these cohorts with established CVD, many individual studies and large meta-analyses have repeatedly demonstrated a strong obesity paradox, where … obese subjects with CVD not only seem to have a much better prognosis than do the underweight CVD patients but also a better prognosis than those with normal BMI levels.” The authors write, “exact mechanisms for the obesity paradox remain unclear” (this is not true, see below) and suggest many possibilities in Table 2 (1). The implication is that extra body fat, which causes CVD, somehow becomes beneficial once people with obesity contract CVD, and that future research must solve this mystery.
To us, the mystery is why journals continue to accept these articles that unnecessarily confuse scientists and the public (2). Randomized controlled trials (RCT) of obese participants with CVD consistently show benefits with intentional weight loss (3–6). The reasons for the nonintuitive findings in the observational trials of patients “with established CVD” have been explained repeatedly, and even cited by Lavie et al. as they noted: “details about the obesity paradox have been questioned, including the potential for collider bias to impact the relationship between obesity and prognosis.” The dismissive phrase, “potential for collider bias to impact …” suggests a misunderstanding of these citations, as the citations explain that the nonintuitive findings are the result of fatally flawed study designs.
Since obesity is associated with the incidence of CVD, then it is a mathematical certainty that collider bias will impact the relationship between obesity and prognosis; only the magnitude of this impact remains unknown. Nonobese participants must have had another cause of the inclusion criteria, CVD. These other causes (e.g., viral, ischemic) create a worse prognosis. Therefore, obese participants do better than nonobese participants, even if extra body fat is harmful in every single study participant (7). Furthermore, as noted since the time of Hippocrates, the dying process causes weight loss (8). Thus, another reason for the nonintuitive findings is that unintentional weight loss becomes associated with death.
If the authors really believe that more fat is better for people with obesity and CVD, they should conduct studies that attempt to answer the question by using unbiased research designs. This could include well-designed observational studies, or studies randomizing participants to programs designed for weight gain. We are confident that such studies will concur with the numerous RCT that consistently find a benefit with intentional weight loss (3–6). Given all of the unanswered questions affecting public health and healthy lifestyle interventions, it is a shame to waste time by repeating and citing studies with flawed designs.
Steven D. Stovitz, MD, MS
Department of Family Medicine
and Community Health
University of Minnesota
Ian Shrier, MD, PhD
The authors declare no conflict of interest and do not have any financial disclosures.
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. 2019; 18:292–8.
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. 2014; 62:96–102.
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