Understanding the integrative role of the central nervous system in the prevalence of obesity and obesity-related diseases is of great importance.  It has been hypothesized that flexibility of food reward–related brain signaling and food cues may differ between overweight and normal-weight subjects and depend on a fasted or satiated state.  Now, a study from researchers at UT Southwestern shows that the brain’s reward centers in severely obese women, before and after fasting, continue to respond to food cues even after they’ve eaten and are no longer hungry, in contrast to their lean counterparts.  The team state that their findings may explain why some people with severe obesity report an underlying drive to eat continually despite not feeling hungry.  The study is published in the journal Obesity.

Previous studies show that the power of food cues targeting susceptible emotions and cognitive brain functions, is increasingly exploited by modern neuromarketing tools. Increased intake of energy-dense foods high in fat and sugar is not only adding more energy, it may also corrupt neural functions of brain systems involved in nutrient sensing as well as in hedonic, motivational and cognitive processing. Recent studies show that only long-term prospective studies in human subjects and animal models with the capacity to demonstrate sustained over-eating and development of obesity are necessary to identify the critical environmental factors as well as the underlying neural systems involved.  The current study investigates functional brain response differences to food in lean and obese women, before and after a meal.

The current study compared the brain activity of 15 severely obese women and 15 lean women.  MRI images of the participants were taken before and after a meal. Results show that both groups exhibited significantly increased activity in the neo- and limbic cortices and midbrain when they were hungry. Data findings show that after eating that brain activity dropped among lean participants while continuing in their obese counterparts.

Results in brain scans show that even after eating and reporting they were full, the severely obese women continued to react to pictures of food in much the same way they had when fasting.  Data findings show that the appeal of pictured food dropped 15% for the lean women after they ate, whilst the severely obese women showed only a 4% decline, based fMRI to measure brain activity. The lab state that after eating, activity in regions in the prefrontal cortex and posterior cingulate cortex significantly changed in the lean group, and not in the obese group.  They observed that the obese study participants maintained activation in the midbrain, one of the body’s most potent reward centers.

The team surmise that their findings show while fasting, brain response to food cues in women did not differ significantly despite BMI. They go on to add that after eating, brain activity quickly diminished in lean women but remained elevated in women with severe obesity.  For the future, the researchers state that the severely obese women in the study, who weighed between 202 and 316 pounds, were candidates for bariatric surgery to lose weight; they are now following these women after surgery to determine if their brain activation patterns change.

Source: UT Southwestern Medical Center