Eat healthy, lose weight, your brain will thank you for it

Losing weight perennially tops the list of New Year’s resolutions. We all have different reasons for this pledge. Maybe we want to fit into our skinny jeans or have more energy to play with our family. Have you ever heard someone say, “I want to lose weight to improve my memory?”

In the last few decades, rates of obesity and related conditions such as type 2 diabetes have skyrocketed in the US and other developed countries. Childhood obesity rates have risen at a particularly alarming clip: Today, about one in five school-age children is obese, and 31 per cent of children are overweight or obese. This is a problem, because obesity is linked with a host of negative health outcomes. It is well known that obesity and diabetes are related to vascular issues such as hypertension, heart disease, and stroke. However, it is less known that obesity is related to our thinking skills (cognition), and even future risk for dementia.

Research suggests that childhood obesity negatively affects cognition. A team of researchers at the University of California San Diego, led by June Liang, reviewed the research on this topic by examining 67 published studies. They found that obesity was related to worse performance on several thinking skills and behaviours, including inhibition (ability to regulate your emotions and behaviours), cognitive flexibility (ability to switch between different tasks), attention, and visuospatial skills. Similarly, childhood obesity appears to hurt standardised testing scores in math and reading. Of concern, children who are overweight are more likely to be overweight in adulthood, pointing to the need to try to combat obesity in children.

Obesity appears to compromise cognition in adults as well as children. In a study led by Séverine Sabia at University College London, researchers studied the relationship between body mass index (BMI) across the lifespan and cognitive function in late mid-life. To do this, the researchers measured BMI in early adulthood (25 years old), early middle life (mean age: 44), and late mid-life (mean age: 61). The study found that being obese at two or three of these timepoints was associated with worse performance on tests assessing memory and executive functioning. Although “executive function” sounds like the job performance of a Wall Street CEO, it actually refers to a cluster of cognitive skills related to planning and controlling behaviour, like organising a project or prioritising tasks. The researchers concluded that chronic obesity negatively impacts your thinking skills in midlife.

Midlife obesity doesn’t just affect the brain in the moment; it also seems to increase the risk for dementia. One twin study led by Weili Xu at the Aging Research Center at Karolinska Institute in Sweden reported that twins who were overweight or obese at

Obesity was related to worse performance on several thinking skills and behaviours, including the ability to regulate emotions and behaviours

midlife were at greater risk for developing dementia, with obese people being at the greatest risk.

But, there’s an upside! Lifestyle factors, such as exercise, can improve our cognitive functions. Research shows that increases in physical activity improve thinking skills. Why might this be? Exercise is thought to improve cognition through various mechanisms. First, aerobic exercise releases a chemical called brain-derived neurotropic factor that stimulates neurogenesis. In plain English, the brain releases a chemical that promotes production of new brain cells. Exercise also reduces insulin resistance and inflammation, which are known to negatively affect cognition and health more generally. Exercise also may improve cognition by indirectly affecting our mood, sleep, and stress levels. Poor sleep, depression, anxiety, and stress are all known to negatively affect brain function. Exercise has been repeatedly shown to improve mood states, stress, and sleep.

So, what’s the take home message here? Obesity is linked to poor cognition and smaller brain volumes. Also, obesity is associated with increased risk for dementia. Despite this bad news, there is hope. Exercise across the lifespan can ameliorate the negative effects of obesity on cognition. A group of researchers in Finland have demonstrated that leisure-time physical activity in midlife and after is associated with decreased risk for dementia and Alzheimer’s disease. Even among older adults with mild cognitive impairment, exercise has been shown to improve cognitive symptoms like memory issues. In conclusion, it’s never too late to start exercising and eating healthier. —Psychology Today