Research has found that obesity leads to the degeneration of white matter (WM) and gray matter (GM) in the brain; this has implications for body movement and sensation, as well as a person’s impulse control (Papageorgiou et al. 2006). In the same way that some drugs are addicting, someone who is addicted to food neurologically loses the ability to say no to eating. Today, the most effective way to treat the physical ailments of obesity is through bariatric, or weight-loss, surgery. Now, the question is can bariatric surgery also ameliorate the neurological and behavioral aspects of obesity?
To answer this question, a study was conducted at the Center for Brain Imaging in Xi’an, China by Dr. Zhang and his research team. The research was funded by the National Natural Science Foundation of China and used brain-imagining technology, specifically the MRI, to observe and calculate white and gray matter densities in study participants over time. They predicted that “there would be measurable neuroanatomical changes in brain regions involving food intake” after obese patients had received weight-loss surgery compared to before surgery (Zhang et al. 2016).
The study was conducted in 2015 and contained an experimental group of morbidly obese (OB) patients (all with a weight under 330lbs) and a control group of normal weight (NW) individuals. According to the World Health Organization, a person must have a BMI, or body mass index, of between 18.5—24.9 to be considered a normal weight (WHO 2018). BMI is the ratio of an individual’s height and weight. The two groups were controlled by age, gender, and education. Each OB patient had a presurgical MRI, or image, of the brain and received laparoscopic sleeve gastrectomy surgery. In this particular surgery, part of the stomach removed, meaning it can hold much less matter than it could originally. Patients who receive this surgery are unable to eat the quantities of food that they formerly could, which in turn promotes weight-loss. OB patients had a post-op MRI a month after the surgery. The NW individuals only had one MRI to serve as a control; the images were used to tell by how much the GM and WM densities deviated between the two groups. All the MRIs were analyzed using the same technology and controls.
The research and its findings were published in 2016 in the International Journal of Obesity. The data collected implied that grey and white matter densities increased as BMI and weight decreased, thus confirming the hypothesis of the researchers. This study provides the first evidence of weight-loss promoting neuroplasticity, or the brain’s ability to change. It also points to bariatric surgery as being even more effective in treating obesity than originally thought; not only does it treat the physical symptoms (excess weight), but also promotes brain growth that better facilitates long-term surgical success.
In today’s context, this research has larger implications. Obesity and its related health problems are becoming a more popular issue as obesity rates rise. According to the World Health Organization, 39% of the world’s inhabitants are overweight and 13% are obese, meaning that almost half of the world’s population is above a normal weight (WHO 2018). Obesity has already been labeled as an “epidemic” and a “public-health crisis” according to the World Health Organization and the Centers for Disease Control and Prevention (CDC 2018). The findings of this study could also be applied to the issue of addiction, as the regeneration of white and grey matter densities have effects on impulse control.
While this study promotes promising findings, there are a few limitations. The authors admitted that there was a small sample size because of the many criteria that the OB group had to meet (could not have previous brain lesions, neurological/psychological disease, or had a waist diameter greater than the interior of the MRI scanner). Originally, there had been 28 participants, but some were excluded by these criteria. Another problem for the researchers was that some participants refused to comply with follow-up scans. The study was conducted in accordance with the Helsinki Declaration; forced compliance cannot ethically be compulsory. There were also no cognitive tests performed in correlation with the study. Another concern is that the research was conducted in China and that the findings have no relevance in the United States. However, a similar study was conducted in Phoenix, Arizona which had very similar conclusions (Pannacciulli et al. 2006).
In the future, experiments elaborating on the findings of this study could use a larger sample size, including a larger variety of weights. Participants of Dr. Zhang’s research could not exceed 330lbs; however, there are obese people who weigh more that might have more severe neurological degeneration. Although replications of this study have already been conducted using more participants (Lui et al. 2018), further experiments could also research the effects of bariatric surgery on diabetes, since diabetes in particular is often linked to poor eating habits and excess weight. Researchers could also experiment with types of weight-loss surgery other than the laparoscopic sleeve gastrectomy, such as the gastric bypass or the gastric band.
Understanding all aspects of obesity helps to create a better standard of care for these patients. As we continue to battle against the obesity epidemic, this and related studies will become integral in the treatment of morbidly obese individuals and education of our healthcare professionals and the general public.
References[CDC] Centers for Disease Control and Prevention. 2018 Aug 13. Adult obesity facts. [accessed 2020 Feb 1]. https://www.cdc.gov/obesity/data/adult.html.
Liu, L., Ji, G. et al. 2019. Structural changes in brain regions involved in executive-control and self-referential processing after sleeve gastrectomy in obese patients. Brain Imaging and Behavior. 13(3): 830-840.
Pannacciulli, N., Del Parigi, A. et al. 2006. Brain abnormalities in human obesity: a voxel-based study. NeuroImage. 31(4):1419-1425.
Papageorgiou, I., Astrakas, L., et al. 2017. Abnormalities of brain neural circuits related to obesity: a diffusion tensor imaging study. Magnetic Resonance Imaging. 37(1):116-127.[WHO] World Health Organization. 2018 Feb 16. Obesity and overweight. [accessed 2020 Feb1]. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight.
Zhang, Y., Ji, G et al. 2016. Recovery of brain structural abnormalities in morbidly obese patients after bariatric surgery. International Journal of Obesity. 40(10): 1558-1565.