A Troubling Gap: Body Size Diversity in Clinical Trials

Marketplace Variations in Violet and GreyIt’s a fact. People come in all shapes and sizes. FDA and pharmaceutical researchers know this. They know that body size and composition can have large effects on how a person responds to drugs. So why do we have such a troubling gap of body size diversity in clinical trials? In the AMA Journal of Ethics, Dania Pagarkar, Erin Harrop, and Lisa Erlanger raise this question:

“Despite concerns about clinical outcomes for patients with obesity, clinical trials have reported few data about participation of and outcomes for such patients.

“Larger-bodied patients remain underrepresented in clinical trials, despite studies showing differences in intervention effects between people with obesity and people with normal BMI. Underrepresentation of people with obesity occurs when researchers exclude participants above a specific BMI, fail to recruit or retain people with obesity, fail to report rates of obesity in study samples, or fail to perform relevant subanalyses.”

Convenient Exclusions

We’ve noted before that scientists and regulators at the FDA know this is a problem. The agency even went to to trouble of convening a workshop on this issue. The commissioner opened it and told the attendees that FDA has no regulatory requirements for body size and weight in clinical trials and their analysis.

Thus, diverse body sizes “continue to be underrepresented in research and in clinical trials, making it difficult to obtain the necessary data to inform dosing of a newly marketed drug in individuals with obesity.”

Diversity can be messy. Because diversity of body size can introduce complexity into clinical trials and interpreting their results, excluding it is simply more convenient. The data comes out more tidy. It prompts fewer questions. Especially if looking into this issue is not a requirement, it’s easier to look the other way.

Leaving a Gap

So we have a gap in the understanding of how to safely and effectively use many prescription drugs in people with obesity. A prime example is brexpiprazole, an antipsychotic drug used in a patient population where most are also living with obesity. Independent research has shown that obesity can profoundly affect the pharmacokinetics of this drug. Yet labeling for this drug makes no mention of the need to adjust its dosing for safe and effective use in people with obesity.

It as as if these patients are invisible or they simply do not count. This gap in drug development and labeling needs to be closed.

Click here for the full article just published by Pagarkar, Harrop, and Erlanger.

Marketplace Variations in Violet and Grey, painting by James McNeill Whistler / The Metropolitan Museum of Art

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July x, 2023

One Response to “A Troubling Gap: Body Size Diversity in Clinical Trials”

  1. July 07, 2023 at 9:24 am, Allen Browne said:


    And it is hard to imagine 40% of adults and 20% of children are invisible or do not count. It sounds like either bad eyesight or bias and stigma (again!).