Alzheimer's risk increases with rise in this 'hidden' body fat, researchers find

Having too much visceral fat has been linked to an increased risk of developing Alzheimer's disease, according to the findings in a new study, but how can you tell this type of fat is a problem if you can't see it?

Visceral fat accumulates inside the abdominal wall, surrounding the body' organs, like the liver and intestines. It's often referred to as "hidden" fat versus subcutaneous fat which forms a layer just below the skin and is the fat that feels oft when poking one's belly. Visceral fat accounts for about 10% of body fat in most people, while the other 90% is subcutaneous fat. 

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In the Alzheimer's study, researchers found that middle-aged people with greater amounts of visceral fat could be connected cognitive function, causing changes in the brain that occur up to 15 years before the earliest symptoms of dementia. Researchers are presenting the findings of their study next week at the annual meeting of the Radiological Society of North America.

The study analyzed data from 54 people between the ages of 40 and 60 who were cognitively healthy and had an average body mass index of 32, which is considered obese in adults. 

The volume of visceral and subcutaneous fats for each person were measured using MRI scans. Researchers also measured their brains, specifically the regions typically affected by Alzheimer's. They found that people with more visceral fat had more of an abnormal protein called amyloid in a portion of the brain affected early during the progression of the disease.

Greater amounts of visceral fat also was found to be linked with brain inflammation, a condition that is thought to be involved in the development of Alzheimer's. Alzheimer's is a brain disorder that slowly destroys memory and thinking skills. There are more than 6 million Americans living with Alzheimer's disease, according to the Alzheimer's Association.

"Even though there have been other studies linking BMI with brain atrophy or even a higher dementia risk, no prior study has linked a specific type of fat to the actual Alzheimer's disease protein in cognitively normal people," study author Mahsa Dolatshahi said in a release. "Similar studies have not investigated the differential role of visceral and subcutaneous fat, especially in terms of Alzheimer's amyloid pathology, as early as midlife."

Here's more about what causes excess visceral fat to collect in the body, other health problems associated with it and how to reduce it:

What causes visceral fat? 

The amount of visceral fat a person is affected by genetic and environmental factors. Genetics determine a person's body shape and how the body stores visceral fat.

Among the environmental factors, an inactive lifestyle and a diet high in fatty foods and carbohydrates can lead to a person having more visceral fat. Stress levels can also play a role: Stress activates the hormone cortisol, which triggers the storage of more hidden fat.

During middle age, the proportion of fat to body weight among women tends to increase more than it does in men, as fat storage begins favoring the upper body over the hips and thighs, according to Harvard Medical School. Even if people are not gaining weight, their waistlines can grow as visceral fat pushes against the abdominal wall.

What other health problems are associated with visceral fat? 

While having some visceral fat is normal and healthy, and it help protect the organs, too much can lead health problems besides Alzheimer's. Fat cells, particularly visceral fat cells, are biologically active. They secrete hormones and potentially dangerous chemicals that affect other tissues and have been linked with a variety of diseases. 

For example, visceral fat makes more of the cytokine proteins that trigger low-level inflammation, which is a risk factor for some chronic conditions like heart disease. It also produces a precursor to the angiotensin protein, which causes blood vessels to constrict and blood pressure to rise. Visceral fat has also been linked with diabetes and stroke.

How can visceral fat be reduced?

While full-body MRIs and body scans are the most precise ways to measure how much visceral fat you have in your abdominal cavity, a less-expensive way to tell if you have excess visceral fat is by comparing the size of your hips to your waist. If the circumference of your waist is larger than the circumference of your hips — or your body would be described as more apple-shaped than pear-shaped — that is an indicator. So is and having blood sugar high enough to be considered diabetic or prediabetic. 

The best way to lose visceral fat is by maintaining a lifestyle that includes exercise and a healthy diet, according to Cleveland Clinic. People should try to exercise for at least 30 minutes each day. This can include cardio, strength training or high-intensity interval training, which particularly has been shown to burn fat faster.

A healthy diet includes lean proteins, whole grains, low-fat dairy, fruits and vegetables, while limiting trans fats, refined sugars, sodium and processed foods. Low-carb diets and intermittent fasting may also help people to lose fat.

Other helpful tips to include getting at least seven hours of sleep per night, reducing stress levels and limiting how much alcohol you drink.