May 19, 2018

Expert reaction to conference abstract (unpublished work) on exposure to chemicals and obesity

Researchers presented a conference abstract at the European Society of Endocrinology annual meeting on exposure to chemicals in the environment and obesity.

Prof Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said:

“I think this is one of the cases where the researcher’s statement that “further studies are needed” is particularly important. To stand up the argument given in the press release, several stages are needed: to establish that the chemicals in question are widespread in the environment, to establish that they can enter the human body through diet or otherwise, to establish that they actually do cause obesity in humans, and to establish that the recommendations in the press release to reduce exposure really do work. Dr Sousa’s group and others have previously provided evidence on some of these, for example on establishing that the chemicals can, and do enter the body in the diet.

“However, there are important gaps; for instance, Dr Sousa and colleagues wrote in a recent learned encyclopaedia article that “up until now, there is no epidemiological evidence supporting the role of organotins in the obesity epidemic.” (Organotins are a class of chemicals that includes TBT, the first chemical to be proposed as an obesogen). In other words, though TBT has been shown to have serious effects in some animals, and has been shown to enter human bodies through food and otherwise, there seems to be a gap in the evidence as to whether it actually causes obesity in people. That’s why the picture isn’t complete yet, and why we should be somewhat cautious about the recommendations.

“It’s also important to bear in mind that this paper hasn’t yet been reviewed by the author’s scientific peers.”

Prof Andy Smith, Senior Scientist, Medical Research Council Toxicology Unit, said:

“This conference abstract appears to be about a review of some past published work with suggestion of future studies of unknown experimental construction.  In my view, without new peer-reviewed studies this is of little scientific value and is just a personal perceptions of the literature.  The global rise in obesity highlighted in this abstract underlines the importance of a healthy diet.

“My concern is that this abstract and press release seem to suggest, without presenting any evidence, that chemicals might be to blame for what are probably mainly lifestyle factors contributing to disease. This suggestion is not based on high quality multi-study investigations.

“What is presented here does not provide any new evidence that these substances are linked to human obesity.”

Prof Jean Golding, Emeritus Professor of Paediatric and Perinatal Epidemiology, University of Bristol, said:

“While it is important to carry out research to identify chemicals in our environments that may influence the development of obesity, as far as I can see there is no research evidence demonstrating that the chemicals and products identified here have caused obesity.  The press release suggests ways in which such chemicals might best be avoided, but there’s no evidence presented about how much obesity they actually cause, or indeed whether they cause obesity in humans at all.  Also, no experimental evidence is given to show that by using the advice given one’s exposure to these chemicals is actually reduced.

“In short, there is no evidence presented here that chemicals cause obesity, or that avoiding them prevents obesity.”

Dr Peter Jenkinson, Toxicologist and Managing Director, Consultancy for Environmental & Human Toxicology and Risk Assessment (CEHTRA) France and UK, said:
“There is no clear evidence presented in this abstract to justify the recommended actions.

“There are some factual errors and misleading statements in the abstract, such as “…that obesogens such as tributyltin – a chemical in anti-fouling paint banned a decade ago… can still be found in food products, in some cases at high concentrations.”  Yet, in their own publication of 2017, on the levels of organotin compounds in the diet, they concluded “Overall our duplicate diet results disclosed low levels of OTs that, according to the current guidelines, does not pose any risk for human health at least in 89% of the samples.”  So it seems that the supposed exposure to ‘obseogens’ may be overstated.

“There is also no mention of exposure levels and no information on whether actual exposure to the substances mentioned have the ability to induce the claimed effects.  Exposure to house dust is mentioned, but dust is primarily made of human skin so 50-100mg, which is not a lot, may only contain trivial amounts of the substances mentioned; no data is provided on this point.

“The author says in the abstract “However, because genes in the population do not change fast enough, other causes must be involved”, which seems to ignore the science of epigenomics.  Epigenomics operates by changing gene expression (not the actual DNA sequence of the gene) over a single generation and such changes can be inherited.

“Some of the recommendations given are sensible BUT not for reasons of obesity avoidance!  Choosing local products, for example, can reduce carbon emissions.

“There is no evidence given in this abstract that indicates that adopting any of these recommendations will actually reduce obesity.”

Prof Russell Viner, President of the Royal College of Paediatrics and Child Health (RCPCH), said:

“This conference abstract must be treated with caution – to place a focus on all its recommendations would be a major mistake.

“Obesogens are unproven but whatever the science eventually shows, they can only play a very minor role in childhood obesity.  Attention must remain on tackling the issues we know need to change.

“Advertising, and the availability of cheap unhealthy food, heavily influences the food choices children make.  We therefore need to make the healthier choice the easier choice.  A ban on advertising food and drink high in salt, sugar and fat on television before 9pm and restrictions preventing new fast food shops opening within close proximity to schools and colleges are two effective ways of doing this.

“For some medical reasons such as protection against allergies, yes, it’s advised to keep a dust free home and so too is removing shoes to avoid bringing in dirt from outside, but these things will not make you a healthy weight.  Only a balanced diet and regular exercise will do that.”

* Abstract title: ‘Environmental contaminants and endocrine disruption: The story of obesogens’ by Ana Sousa.  This is a conference talk that was discussed at the European Society of Endocrinology annual meeting, on Saturday 19 May 2018.  There is no paper as this is not published work.

Declared interests

Prof Kevin McConway : “Kevin McConway was the lead author of a chapter on Measurement and Communication of Health Risks from Pollution for the 2017 Annual Report of the Chief Medical Officer ‘Health Impacts of All Pollution: what do we know?’. He is a member of the Science Media Centre’s Advisory Committee.”

Prof Andy Smith: “I have no conflict of interests other than being a member of UK and EU committees and working groups who have to look at information critically before issuing advice.”

Prof Jean Golding: “I have no conflict of interest.”

Dr Peter Jenkinson: “I declare that I do not have any interest in this work or publication.”

None others received.