If you're overweight but just can't resist the temptation of high-fat foods don't beat yourself up. Your inability to say no could be wired in your brain. Research shows that there is a direct relationship between obesity and the brain's prefrontal cortex, the part of the brain that is responsible for logical reasoning, decision making and self-control.
According to longitudinal studies, people with an inactive prefrontal cortex tend to increase their food intake more than those with a normal brain structure. The reason is that this area of their brain has a lower gray matter volume. This area of the brain is responsible for regulating movement, emotion and memory, so a reduced gray matter volume in obese participants explains why they cannot curb their appetite and accumulate excess fat tissue, which results in an increased body weight due to a high body mass index.
Research also shows a direct link between obesity and the brain's white matter. The white matter volume in middle-aged adults with obesity problems is lower than that of normal-weight people of the same age. Due to reduced white matter tracts in obese adults, their cognitive function is compromised, so they tend to eat more than they should as their brain cannot process information correctly and tell when they've had enough food. Maintaining white matter integrity in the brain is important as it enables the brain's neurons to communicate with each other to ensure optimal neurocognitive function.
The links between obesity and impaired executive functions should be taken seriously since evidence indicates that brain structural changes can put even healthy people at risk of morbid obesity. Studies show that people of normal weight who have sustained a brain injury can experience excessive weight gain, which may potentially lead to abdominal obesity. This is particularly true for obese adults whose hypothalamus, the part of the brain responsible for regulating vital body functions such as blood pressure and heart rate, has been damaged.
Source: Obesity Canada
By failing to address brain structural changes, a vicious cycle of increasing one's food intake, especially caloric intake, is perpetuated whenever an external stimulus triggers the brain to crave food. Catching a glimpse of an image or advertisement of food, for instance, can lead a person to binge straightaway, leading to weight gain, a wider waist circumference and ultimately the development of obesity. These are among the risk factors for metabolic diseases, cardiovascular disease and other chronic conditions.
High Fat Diets Insulate Brain Cells
Based on their findings from conducting a brain scan or magnetic resonance imaging on obese participants, researchers have long established the association between obesity and poor cognitive function.
A study led by Monash University in Melbourne has found a high-fat diet can cause brain cells to become insulated, preventing vital signals that tell the body to stop eating from reaching the different brain regions efficiently.
Dietary interventions, such as cutting back on portion sizes, managing meal times, and avoiding sugary drinks and food, will increase leptin levels and promote weight loss. Produced by the adipose tissue located in the small intestine, leptin is a hormone that regulates energy and hunger to curb the amount of body fat. In other words, higher leptin levels can counteract the effects of obesity.
Too Much Eating, Too Little Exercise
If a high-fat diet insulates brain cells there are "two clear outcomes", says Professor Michael Cowley, former Australian Life Scientist of the Year and Director of Monash Obesity and Diabetes Institute (MODI) where the study was done. First, the brain is unable to detect when the body is full and to stop eating. Secondly, the body can't detect signals to increase energy use and burn off kilojoules/calories.
Regular exercise will not only reduce body fat but also counter the dangerous consequences of physical inactivity to the brain and improve cognitive performance. With better executive functioning, the body's ghrelin levels go down, hence reducing food intake. Several studies have shown a direct relationship between obesity and the hormone ghrelin, which is produced in the stomach to regulate hunger. Obese adults are found to have constantly high ghrelin levels, which explain their constant cravings for high-calorie foods and sugary drinks.
Tendency to Obesity May Be Present at Birth
The neuronal circuits regulating eating and energy expenditure are naturally occurring processes in the brain, says Professor Cowley. But if a person's brain cells become insulated, this process is impaired. "The circuits begin to form early in life so that people may have a tendency towards obesity even before they eat their first meal," Professor Cowley says. He says this finding provides a critical link in addressing the obesity epidemic.
According to previous studies on the prevalence of obesity, not all obese adults have poor cognitive functioning, which leads to unhealthy eating habits. The genetic makeup of some obese adults causes them to gain more weight than normal-weight people, which is why non-food addicted obese people constantly accumulate excess fat even if they aren't overeating.
The scientific community says future studies on gene mutations that cause obesity from birth need to be conducted before they can establish positive associations between obesity and genetics.
Losing Weight Not Just Lack of Willpower
Eating a high-fat diet causes more "insulation" in the cells, making it harder for the brain to help a person lose weight. "Obese people are not necessarily lacking willpower. Their brains do not know how full or how much fat they have stored, so the brain does not tell the body to stop refuelling. Subsequently, their body's ability to lose weight is significantly reduced," Professor Cowley said.
The study was done in collaboration with scientists at Yale School of Medicine in the United States, along with other scientists in Cincinnati, New Jersey, Mexico and Spain.
By analyzing the brain function of obese participants, these studies have demonstrated that the only way to address the prevalence of obesity is by working with the functional connectivity of the brain. A reduced brain volume as a result of high amounts of body fat affects the brain's synaptic plasticity, but improving one's diet and physical inactivity with the right diet and behavioral interventions will no doubt keep the effects of obesity at bay.
So the next time you berate yourself for lacking the willpower to lose weight, go easy on yourself. The consequences of obesity may be wired in your brain and you may need the assistance of a health professional who specialises in brain health to restore your brain's synaptic plasticity, or neuronal communication, and improve cognitive function.
Originally published on Apr 14, 2011
