Wednesday, 16 May 2012

Autism and obesity

Not a day seemingly goes by in the world of peer-reviewed science when a paper isn't published somewhere in the world suggesting an association between obesity and ...... [fill in the blank] to account for the 'obesity epidemic' we constantly hear about. Gone it seems, are the days of the rather over-simplified relationship between balancing energy in and energy out to be replaced with something altogether more complicated despite some lingering prejudice. Genes, environment, biochemistry and even that old favourite gut bacteria, have all found themselves in the frame as moderating the risk of obesity. Food intake, eating patterns and exercise should of course be given their fair dues in terms of obesity and being overweight, but not it appears exclusive rights.

Indeed in recent weeks, obesity has even found itself being tied into autism as per the study by Krakowiak and colleagues on maternal obesity and risk of autism. As perhaps expected, this study was not exactly received with welcome arms; to quote one mum's rather entertaining description "I am a big fat load and my out of control eating caused my son's autism". Satire of course, but with an important message about 'association' and 'risk' and their communication in science.

Continuing the autism-obesity speculation, a new paper by Jyoti Rajan Sharma and colleagues* (full-text) has entered the frame reviewing the evidence for a link between autism and obesity. Just before you click away, perhaps to IMFAR 2012 in Toronto, thinking that this topic is probably not going to be too interesting, bear in mind that people with autism have at least the same risk as everyone else of presenting with weight issues as per the old mantra: a diagnosis of autism is seemingly protective of nothing.

I'm not going to go into excruciating detail about this paper aside from the fact that it discusses some important issues:

  • the differing prevalence rates for obesity in cases of autism worldwide (covered in a past blog post),
  • the very wide range of possibilities which might affect the weight of people with autism such as dietary choices, physical activity levels and importantly, side effects associated with pharmacotherapy,
  • the genetic overlap between autism and obesity - that is, the genetic findings which seem to cross both conditions, 
  • the overlap between medications used in cases of autism and those used in obesity.

As with any review paper, there is very little in the way of novel material emerging from this manuscript in terms of new scientific findings. That being said, the authors' suggestions that at a genetic level, there may be some sharing of findings between autism and obesity is interesting and could potentially pave the way for future studies for example, looking at cases of obesity in autism as a kind of endophenotype. The obvious caveats being the requirement to see this with the appropriate non-autism control groups as comparators and the need to look at epigenetic issues as well as genomic changes.

I don't want to underplay the role that diet and physical activity can have on weight, and how autism, like many other conditions, can often be associated with various health and social inequalities compounded by external issues resulting from medication use for example. Whether however common threads predisposing to obesity and related biological parameters (e.g. metabolic syndrome, cholesterol findings - with some interesting observations in cases of autism) might be prevalent in cases of autism, is an interesting field and bearing in mind the physical health consequences, something perhaps requiring quite a bit more inquiry.

* Sharma JR. et al. Autism and obesity: prevalence, molecular basis and potential therapies. Autism Insights. May 2012.
DOI: 10.4137/AUI.S9138