How fat arms can be the sign of so many health conditions including dementia. Doctors reveal the exact circumference that puts you in danger

We’ve long been told to watch our waistlines. Along with a high body mass index (BMI), excess belly fat is a warning sign of health problems like heart disease and type 2 diabetes. An adult BMI over 25 is considered overweight, while 30 or higher is obese.

But should we look for warning signs elsewhere? Our arms?

If the circumference of the arm (halfway between the shoulder and the elbow) is more than 32 cm (12.5 inches), there is a good chance that a person is obese. Recent studies also show that more fat around the arms increases the risk of Alzheimer’s, heart disease, fatty liver disease and even osteoporosis.

In some cases there was an increased risk even if the BMI was healthy.

Like the fat stored around the legs, arm fat was previously thought to be largely benign, or at least less harmful than fat stored around the belly. This is a sign that someone also has more visceral fat (a more harmful type of fat stored in and around our organs).

However, research published a few weeks ago by scientists from Sichuan University in Chengdu, China, suggests otherwise. The researchers analyzed data from 412,000 people in the United Kingdom over a nine-year period to identify possible links with Alzheimer’s and Parkinson’s disease.

The volunteers had their waist and hip sizes, arm circumference, fat mass (a measure of total body fat), and muscle mass (the same, but for muscle) measured.

People with excess belly fat were 13 percent more likely to develop the disease than those with low belly fat.

Previous research has suggested that belly fat may be linked to Parkinson’s disease (a gradual loss of brain cells that causes tremors, stiffness, slow movement and freezing). It disrupts insulin levels and triggers a complex reaction that leads to a drop in dopamine, the brain chemical that helps regulate movement.

However, the new research also shows that people with more arm fat have an 18 percent higher risk of Alzheimer’s or Parkinson’s and are also more likely to develop heart disease.

In contrast, people with muscular arms, rather than flabby arms, were found to be 26 percent less likely to develop either condition.

Based on their findings, the researchers suggested that a program aimed at reducing fat and building muscle in the arms might be more effective at preventing these problems than general weight loss.

The new research also found that people with more arm fat had an 18 percent higher risk of developing Alzheimer’s or Parkinson’s, as well as a higher risk of developing heart disease.

These aren’t the only serious diseases that could be linked to arm fat. Research presented in May at the European Congress of Endocrinology showed that measuring arm fat could be used to identify people at risk of spinal fracture due to undiagnosed osteoporosis.

Researchers from the National and Kapodistrian University of Athens studied people in their 50s and 60s with no history of the disease. They found that people with high visceral fat had poorer quality bone in the spine, putting them at risk of life-changing fractures.

But the same was true for people with fat arms, even if they were not obese according to their BMI.

In the study, the researchers used a caliper, an instrument that “pinch” the skin to measure the fat underneath.

Arm fat is thought to be a marker for hidden visceral fat. Visceral fat is known to release inflammatory chemicals into the blood that can accelerate bone loss.

These findings may be important because many people are only diagnosed with osteoporosis after they have suffered a bone fracture.

Eva Kassi, a professor of endocrinology who led the study, said: ‘Surprisingly, we found that arm fat mass is negatively associated with bone quality. It could mean that arm fat becomes a useful indicator of spinal bone quality.’

A study from Wenzhou Medical University in China, published in May in Frontiers In Public Health, found that children between the ages of 12 and 18 with a larger arm circumference are 25 percent more likely to have dangerous amounts of fat around the liver, known as nonalcoholic fatty liver disease (NAFLD).

NAFLD is linked to obesity and poor diet and can lead to scarring (cirrhosis), liver failure, or cancer.

Should we all measure our arms instead of our waist?

Not yet, says Wasim Hanif, professor of diabetology and endocrinology at the University Hospital Birmingham, because fat in the upper arm is much less ‘metabolically active’ – the type of fat linked to chronic disease.

“The worst kind of fat is visceral fat in the belly because of its association with type 2 diabetes and heart disease,” he says. “If I had to choose between a big belly or big arms, I would always choose the arms.”

However, some researchers are still convinced that arm fat is important. Professor Kassi’s team plans to expand their bone health studies to see if they can identify younger men and women – in their 30s – who may be at risk of osteoporosis, based on fat levels in their arms.

People at high risk are given an exercise program to burn arm fat, in the hope that this will reverse the damage to the bones.