What does excess weight do to your brain in the long run?
Excess weight harms your brain in multiple ways at once: less brain tissue, weaker connections and a higher risk of dementia. Exercise combined with diet appears to be able to partly reverse this, so losing weight is good for your brain too.
Excess weight damages brain tissue in multiple places at once. Neuroimaging studies consistently show that people with obesity have less grey matter volume (the brain's processing layer) and weaker connections in the white matter (the 'wiring'). The brain regions most affected are those involved in reward, decision-making, memory and attention.
One important mechanism is chronic low-grade inflammation. Excess weight causes a persistent, smouldering inflammatory response throughout the body. This inflammation can damage the blood-brain barrier and disrupt the brain's waste-clearance system. As a result, harmful substances accumulate in brain regions around the hypothalamus. This raises the risk of cognitive decline and dementia. The mechanism is well described, but direct causality in humans has not yet been conclusively proven.
A second mechanism runs via insulin. In people with excess weight and type 2 diabetes, the brain becomes less responsive to insulin. This disrupts not only metabolism and eating behaviour, but also cognitive function. Brain scans in humans show visible changes in how active different brain regions are. This has been linked to an increased risk of dementia.
The combination of abdominal fat and depression is particularly harmful to cognition. This emerges from a large analysis of more than 114,000 people aged 45 and older across four countries. Abdominal fat alone already had a negative effect, but together with depression that effect was statistically robust across all cohorts. The decline in cognitive performance is modest but measurable.
The good news is that the damage appears to be partly reversible. A small study in women with excess weight after menopause showed that three months of exercise combined with a diet improved memory and planning ability. Exercise alone also helped memory; diet alone had no measurable effect. Intermittent fasting does not appear to improve cognition in healthy people, and whether it helps in people with excess weight is still being investigated.
Claims are based on neuroimaging studies, observational cohorts (totalling >114,000 participants), animal models and one small RCT (n=92). The associations are consistent, but direct causality in humans has not yet been fully proven for the underlying mechanisms.
What does alcohol do to your brain in the long term?
Long-term heavy drinking demonstrably damages the brain, in part irreversibly. Stopping helps, but after years of heavy use it should always be done under medical supervision.
What does long-term loneliness do to your brain?
Prolonged loneliness is associated with a higher risk of dementia and persistent low mood, and damages the stress system. Staying socially active has a modest but measurable protective effect, so investing in regular social contact is worthwhile.
What does air pollution do to your brain in the long run?
Long-term exposure to fine particulate matter is associated with a higher risk of dementia and cognitive decline, even at younger ages. The evidence is not yet watertight, but strong enough to take air quality seriously when making choices about where to live and how to get around.
Does your brain age faster than the rest of your body?
Whether your brain ages faster than the rest of your body varies from person to person, but the consequences are significant: a biologically old brain increases the risk of Alzheimer's more than threefold. Keep an eye on your blood pressure, sleep and lifestyle, as these have the most demonstrable influence on brain ageing.
Does watching a lot of television affect your brain?
Watching more than 3.5 hours of television per day is associated with faster memory decline in people aged 50 and over, although it has not been proven that watching television itself is the cause. Balance long stretches in front of the screen with activities that challenge your brain more.
Is it bad for your brain if you don't get enough exercise for years on end?
Years of too little exercise is associated with a clearly elevated risk of memory problems and dementia. Moving more, even lightly, is the most concrete form of protection you can build in.