"The findings suggest that a considerable number of patients before and after bariatric surgery screened positive for ADHD [attention-deficit hyperactivity disorder]. It can be hypothesized that some core ADHD symptoms improve after surgery."
Bariatric surgery, where several surgical options are available to aid weight loss in those who present with 'dangerous' obesity, was the topic of the paper by Nielsen and colleagues  (open-access available here) who set out to compare "pre- and post-bariatric surgery patients using the internationally used Conners' Adult ADHD Rating Scale (CAARS™) to screen for ADHD" among other measures. The authors came up with some interesting details. They reported that the rate of 'probably ADHD' (defined using the CAARS and also the Wender Utah Rating Scale Short Version (WURS-k) cut-off scores) were 8.3% in their pre-surgery sample (n=120) and 6.3% in their post-surgery sample (n=128).
When looking at the behavioural profiles of those pre- and post-surgery, there were some not entirely unexpected differences when it came to items related to depression and eating-related psychopathology - both scoring lower in the post-surgery participants. But also those post-surgery reported some potentially important information in relation to generally better attention and memory compared to pre-surgery participants. I was intrigued by the authors explanation of this: "The finding of a better attention and memory function in the post-surgery sample is in line with the results of longitudinal studies demonstrating improvements in cognitive functioning following bariatric surgery." Further: "It is reasonable to assume that postoperative cognitive improvement in attention and memory might have impacted the self-report on the respective CAARS subscale." Does this imply that bariatric surgery might act as some kind of nootropic for [some of] those with obesity?
In these days of ADHD being 'linked' to obesity (see here), the Nielsen results fit nicely. Alongside the idea that weight loss surgery might link into improved cognitive functioning and onwards, impacting on facets of ADHD I'd have to question what the biological mechanism(s) might be. Does the restriction of food intake as a consequence of surgery indicate a role for food in some cognitive processes? Does such surgery potentially impact on the trillions of wee beasties that populate our gut and then onwards exert an effect of cognitive processes? There are several questions that still need answering...
 Nielsen F. et al. Attention Deficit Hyperactivity Disorder Prevalence and Correlates Pre- and Post-Bariatric Surgery: A Comparative Cross-Sectional Study. Obes Facts. 2017 Jan 20;10(1):1-11.
Nielsen F, Georgiadou E, Bartsch M, Langenberg S, Müller A, & de Zwaan M (2017). Attention Deficit Hyperactivity Disorder Prevalence and Correlates Pre- and Post-Bariatric Surgery: A Comparative Cross-Sectional Study. Obesity facts, 10 (1), 1-11 PMID: 28103594