Recent research has revealed a concerning correlation between an expanding waistline and the onset of Alzheimer's disease. The study indicates that as a person's belly size increases, their brain's memory center may diminish, and potentially harmful substances such as beta amyloid and tau proteins might emerge. These changes can occur as early as in one's 40s and 50s, long before any cognitive impairment becomes evident.

Beta amyloid plaques and tau tangles are indicative of the brain's early progression towards Alzheimer's, with amyloid plaques typically appearing first, followed by tau tangles as the disease advances. Dr. Cyrus Raji, a senior study author and associate professor of radiology at Washington University School of Medicine in St. Louis, explains, "The higher the levels of amyloid or tau in the brain, the more severe the brain's condition becomes. We can monitor a deteriorating brain through reduced blood flow.

Additionally, we've observed brain atrophy, specifically in the hippocampus, which is a part of the brain's memory center." Reduced blood flow to the brain's memory center may lead to shrinkage, which is another significant biomarker for Alzheimer's, according to Dr. Richard Isaacson, a preventive neurologist and director of research at the Institute for Neurodegenerative Diseases in Florida.

Obesity is recognized as a global epidemic by the World Health Organization, which predicts that over half of the world's population will be overweight or obese within a decade. In the United States, it is estimated that nearly 260 million Americans will be overweight or obese by 2050 if immediate policy actions are not taken. Dr. Raji states, "At least 1% of American adults are at risk of dementia due to obesity, which translates to over 2 million individuals potentially developing Alzheimer's disease as a result of their weight."

This issue is a significant public health concern, as obesity in middle age, particularly in one's 40s and 50s, is a risk factor for Alzheimer's disease, which typically manifests symptomatically in later decades. A pilot study conducted by Dr. Raji and his team in November 2023 discovered a link between a specific type of deep abdominal fat, known as visceral fat, and inflammation and amyloid accumulation in the brains of 32 individuals aged 40 to 50. At that stage, the presence of tau was not confirmed. Visceral fat envelops the body's major organs and is distinct from subcutaneous fat, which constitutes approximately 90% of the body's fat, as reported by the Cleveland Clinic.

Dr. Raji clarifies, "Most of a person's body mass index (BMI) reflects subcutaneous fat, not visceral fat. We measure visceral fat using abdominal MRI and employ a specialized computer program to quantify the actual volume of visceral adipose tissue."

The study also utilized amyloid positron emission tomography (PET) scans, considered the gold standard, to verify the presence of amyloid and tau in the participants' brains, and magnetic resonance imaging (MRI) to assess the levels of visceral fat associated with expanding waistlines. Dr. Raji notes, "The more visceral fat an individual has, the greater the inflammation in the body, which is significantly worse than the inflammation associated with subcutaneous fat."

Visceral fat, due to its proximity to organs, receives more blood flow and is more hormonally active than subcutaneous fat. The study also investigated insulin resistance through fasting plasma insulin levels and glucose tolerance tests, finding the highest insulin resistance in those with greater amounts of visceral fat. Dr. Raji remarks, "Visceral fat is the more metabolically abnormal fat that can induce diabetes."

The study further established a connection between deep belly fat and brain atrophy in the hippocampus, another biomarker for Alzheimer's disease. The research has since expanded, adding 48 more participants, totaling 80. The average age of the participants was 49, with an average BMI of 32, which is considered obese by medical standards. Dr. Raji shared updates on the findings at the Radiology Society of North America's 2024 conference, stating, "We demonstrate for the first time that higher amounts of visceral or hidden fat are related to abnormally high tau proteins in individuals up to 20 years before they could develop the earliest symptoms of Alzheimer's disease. Previously, we had only shown a link between visceral fat and amyloid." The PET scans revealed that as visceral fat levels increased, so did the levels of both amyloid and tau, according to the new research.

Dr. Isaacson emphasizes the importance of smart strategies to reduce belly fat that can reverse these trends. He advises not to focus solely on body weight but also on body composition, which can be monitored at home using a biometric scale or through an annual DEXA scan ordered by a healthcare provider. Exercise is crucial, but it should be done more efficiently, not just harder.

Dr. Isaacson suggests taking brisk walks at a steady pace, working up to at least 45-60 minutes two to three times a week, following what experts call "Zone 2 training." This can be tracked by being able to converse while exercising, albeit barely. He also recommends walking fast on a treadmill at a slight incline or walking with a weighted vest to enter the fat-burning zone more quickly and efficiently. Building muscle mass is also key, as more muscle leads to a higher metabolism and better fat burning throughout the day. If muscle mass is low, strength training for at least 30 minutes twice a week or more is advised, along with ensuring adequate daily protein intake.