People with excess stomach and arm fat are more likely to develop Alzheimer's or Parkinson's, according to a new study.

Researchers have discovered that those who carry weight in these areas — often dubbed 'beer bellies' and 'bingo wings' — appear to have a higher risk of the diseases, while people with more muscle are at a lower risk.

The study involved 412,691 people in the UK, average age 56, who were followed for nine years.

At the beginning of the study, measurements were taken for body composition, such as waist and hip measurements, grip strength, bone density and fat and lean mass.

During the study, 8,224 people developed neurodegenerative diseases — mainly Alzheimer's disease, other forms of dementia, and Parkinson's disease.

After adjusting for other factors that could affect the rate of disease, such as high blood pressure, smoking and drinking status and diabetes, researchers found that overall people with high levels of belly fat were 13 per cent more likely to develop these diseases than people with low levels of belly fat.

People with high levels of arm fat were 18 per cent more likely to develop the diseases than those with low levels of arm fat.

However, those with high muscle strength were 26 per cent less likely to develop the diseases than those with low levels of strength.

Study author Professor Huan Song, from Sichuan University in Chengdu, China, said: 'These neurodegenerative diseases like Alzheimer's and Parkinson's affect over 60 million people worldwide, and that number is expected to grow as the population ages, so it's crucial that we identify ways to modify risk factors to develop some preventive tools.

'This study highlights the potential to lessen people's risk of developing these diseases by improving their body composition.

'Targeted interventions to reduce trunk and arm fat while promoting healthy muscle development may be more effective for protection against these diseases than general weight control.'

The link between bingo wings and belly fat and these diseases was partly explained by the occurrence of heart disease and stroke during the study, the researchers said.

'This underscores the importance of managing these cardiovascular diseases right away to help prevent or delay the development of Alzheimer's, Parkinson's, or other degenerative diseases,' Professor Song said.

The Alzheimer's Society reports there are around a million people living with dementia in the UK today. This is projected to rise to 1.4 million by 2040.

Meanwhile there are around 153,000 people in the UK living with Parkinson's, which can cause symptoms such as tremors, stiffness and slowness of movement.

The findings were published in the journal Neurology.