A recent study by researchers at Georgia Regents University in Augusta gathered evidence that excess fat alters brain function, at least in mice. The study, published in February in The Journal of Neuroscience, not only supports previously gained knowledge that obesity negatively affects both memory and learning skills, but goes on to determine how excess fat can influence the brain. Until now, researchers did not understand how weight could modify cognitive abilities.
While fat cells create substances that flow through the bloodstream into numerous body parts, the brain lies behind a protective barrier that generally blocks undesirable molecules from entering. When the substance, namely interleukin 1, is released through the bloodstream, it begins biochemical processes that generally lead to inflammation and poor health. According to medical professionals, the passage of interleukin 1 into the brain, specifically the hippocampus, should not be possible. The hippocampus is the area of the brain which is in control of both learning and memory.
What researchers found upon examination of the mice was that the interleukin 1 had entered the brain and was subsequently causing cognitive impairment. The mice were found to have low levels of those biochemicals associated with healthy synapse function as well as high levels of inflammation. Synapses connect neurons and aid message communication in the brain. Traffic patterns of neural activity become negatively affected when synapse health fails. Additionally, if inflammation continues for a long period of time, it eventually hurts the cells.
What research found was that the obese mice performed poorly on memory and reasoning tests, even those in which they previously did well. Original researchers wished to determine if it was the obesity itself affecting the brain or some other physiological factors. To that end, the study’s overseers simply removed the majority of the fat. When the mice recovered, their interleukin 1 levels were almost non-existent. When the surgically reduced mice were run through the same tests they failed pre-surgery, they began to perform very well. To test this further, the scientists took the fat preserved from the obese mice and implanted it into lean mice. These mice began to perform poorly almost immediately after surgery.
The findings, though convincing, were of little practical value to any human patients. The amount of fat removed from the mice was of a percentage that would be impossible to excise in a person. Scientists were of the belief that fat was impairing cognitive function but felt the need to find alternative solutions.
They came up with an experiment that was far less invasive then surgery. The scientists used mice prone to obesity and allowed them to gain weight. When the mice became heavy enough, they began half on a daily 45 minute exercise program and allowed the remaining mice to remain sedentary. Although the mice required to exercise did not lose much weight, they did lose significant fat. These mice not only had biochemical levels that indicated healthy synaptic functioning, they also exhibited low levels of inflammation, and performed much better in testing procedures than the obese mice.
The results indicated that, regardless of actual weight, the difference in overall fat amounts determined if cognitive functioning levels would be higher or lower. These studies were performed on mice, not humans, and therefore may not be indicative of how a human brain may respond to body fat. While the studies may not reveal how the human body reacts to fat, there is no current evidence to the contrary. The possibility remains that humans, as with mice, may experience cognitive impairment due to nothing other than body fat. It is possible, therefore, that obesity in humans may negatively affect the brain and how it functions.
By Dee Mueller