What Does Obesity Have to Do With Alzheimer’s Disease?

A hormone that helps manage weight is also linked to cognitive changes.

Reviewed by Michelle Quirk

Key points

• Leptin, a hormone that helps with weight control, also plays a role in normal cognition.
• Leptin resistance occurs when the hormone is secreted by fat cells but unavailable for use by the body.
• Leptin resistance causes further weight gain in obesity as well as cognitive changes in the brain.

Reduced availability of leptin, a hormone that helps you maintain a healthy weight by regulating your appetite and helping to maintain energy balance, has been found to play a role in the development of late-life dementia, according to a study published by a group of American and international researchers in the September 2024 issue of Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

Hormone Resistance

The job of all hormones is to signal instructions or send messages through the bloodstream to specific receptors on targeted cells throughout the body. Once recognized by the receptors, the message is relayed and the cell reacts accordingly. When the hormone can’t bind with its receptors due to defects or some other interference with signal transmission, a condition known as hormone resistance develops, and the message is not received or acted upon by its target cells. The result can be high levels of leptin circulating in the bloodstream with no place to land.

In addition to helping control how much food you eat by sending signals of hunger and fullness, leptin normally plays roles in brain cell development, structure, plasticity, and protection. When obesity is associated with leptin resistance due to a high-fat diet, aging, or genetic inheritance, it can also lead to diminished leptin signaling in areas of the brain associated with cognitive function.

The Connection to Cognition

As researchers have discovered in recent years, leptin’s extensive biological activities have the capacity to alter many brain functions related not only to weight control but also to learning, memory, motivation, and other cognitive functions. Normal leptin levels are associated with maintaining the integrity of white matter in the brain and lowering the risk of impaired cognition and dementia. When obesity is a result of leptin resistance, all of these cognitive functions can be negatively impacted.

Previous studies of elderly people have already established this road from obesity to late-life cognitive impairment, Alzheimer’s disease, and dementia due to leptin resistance. This latest study looked more closely at fat tissue in the body that produces leptin, with researchers concluding that compromised leptin resistance associated with obesity in middle-aged people can also increase the risk of cognitive impairment later in life, suggesting there might also be a pathway to prevention or lowered risk in younger men and women.

What You Can Do

What’s good for your heart is good for your brain, according to the Alzheimer’s Foundation of America. That includes staying fit and maintaining weight within a healthy range by remaining active and eating a heart-healthy, low-fat diet rich in fruits and vegetables and limited in red meat, processed foods, fried foods, sugar, and salt. That also includes getting enough sleep, staying socially connected, keeping your mind stimulated and challenged, understanding the effects of different types of medications, limiting alcohol, and quitting smoking, if necessary. It also means getting annual health screenings and check-ups to monitor conditions that can have a negative impact on your brain, including obesity, diabetes, high blood pressure, and cardiovascular disease.