Is Obesity Linked to ADHD?
As more and more children consume high-fat diets and become increasingly overweight, the incidences of diseases like type 2 diabetes and high blood pressure have steadily grown among the population. However, these may not be the only health issues linked with this surge in overeating among children. In a recent study from the University of Illinois, researchers have found that high-fat diets may also be associated with impulsivity, depression, anxiety and ADHD.
They used four-week old mice to see if bio-behaviors would be affected by placing the animals on a high-fat diet for one to three weeks. The mice were randomly divided into two groups; the first group ate a diet in which 60% of the calories were from fat, and the second group ate a diet in which only 10% of the calories were from fat. After one week of eating a high-fat diet, the mice in group one exhibited an increase in anxiety levels as evidenced by more time spent burrowing and wheel running. In addition, the mice in group one were hesitant to explore open quadrants of a zero maze. They were also unable to navigate a Y-maze and recognize a new object.
When the researchers analyzed the cortex, hippocampus and hypothalamus for dopamine in the group one mice, they found increased levels of homovanillic acid (HVA) in the hippocampus and cortex. HVA is a byproduct that results when dopamine is metabolized. That means that the dopamine levels in the group one mice were low. Dopamine is important because it is a neurotransmitter that sends impulses from a nerve cell to another nerve, organ or tissue. Low levels of dopamine negatively impact the ability to think, focus and concentrate. It also affects motor coordination. Individuals with Parkinson’s Disease have low levels of dopamine.
Dopamine levels in another part of the brain called the dorsal striatum control an individual’s ability to enjoy rewards like eating. A poorly functioning dorsal striatum in which dopamine cannot signal to the brain that enough food had been consumed would lead to excess consumption, resulting in obesity.
The high level of HVA in the animals’ hippocampus and cortex was associated with a decreased presence of the BDNF gene in the cortex, which means that the levels of the protein it produces were also decreased. This protein helps existing neurons survive and aids in the growth of new neurons. Without those neurons, learning and memory would be affected.
The researchers also discovered that giving the group one mice Ritalin reversed the damage to learning and memory caused by eating the high-fat diet. Giving them the antidepressants Vestra and Norpramin had no effect on the memory and learning impairment.
Kaczmarczyk, M., Machaj, A., Chiu, G., Lawson, M., Gainey, S., York, J., Meling, D., Martin, S., Kwakwa, K., Newman, A., Woods, J., Kelley, K., Wang, Y., Miller, M., & Freund, G. (2013). Methylphenidate prevents high-fat diet (HFD)-induced learning/memory impairment in juvenile mice Psychoneuroendocrinology DOI: 10.1016/j.psyneuen.2013.01.004
Stice, E., Spoor, S., Bohon, C., & Small, D. (2008). Relation Between Obesity and Blunted Striatal Response to Food Is Moderated by TaqIA A1 Allele Science, 322 (5900), 449-452 DOI: 10.1126/science.1161550