Loneliness shortens lifespan as much as being obese, a study has found.

Whether a person feels alone is as much of a predictor of whether they will die prematurely as their weight, researchers found.

And they predict a loneliness 'epidemic' in the future as more people live alone - and warn people need to start taking social relationships more seriously.

They explained loneliness and social isolation can take different forms. For example, someone may be surrounded by people but still feel alone.

Other people might isolate themselves because they prefer to be alone.

The effect on lifespan, however, is the same for those two scenarios, researchers found.

Feeling alone or isolated can shorten a person's lifespan as much as being obese, a study found (file photo)

'The effect is comparable to obesity, something that public health takes very seriously,' said Julianne Holt-Lunstad, of Brigham Young University, Utah, the lead study author.

'We need to start taking our social relationships more seriously.'

And the link between loneliness and the risk of death is stronger among yonger people, they found.

Although older people are more likely to be lonely and face a higher risk of death, loneliness and social isolation better predict premature death among groups of people younger than 65 years.

This is worrying given the increasing trend for living alone, researchers said.

'Not only are we at the highest recorded rate of living alone across the entire century, but we're at the highest recorded rates ever on the planet,' said Tim Smith, co-author of the study.

'With loneliness on the rise, we are predicting a possible epidemic in the future.'

The study analysed data from a variety of health studies.

Altogether, the sample included more than three million participants from studies that held data for loneliness, social isolation, and living alone.

DOES HAVING FEWER FRIENDS MAKE US LESS LONELY? For most people the idea of losing friends overtime can leave them fearful of being alone in old age. But new research suggests that having fewer friends can actually make us less lonely. A study that examined the friendships of nearly 400,000 students has shown that while the number of close friends they have on average has fallen in the past 25 years, they feel less isolated. Psychologists believe modern technology and the increased use of social media to interact with other people, and has led to the decline in face-to-face contact, has driven this change. Advertisement

Controlling for variables such as socioeconomic status, age, gender, and pre-existing health conditions, they found that the effect goes both ways.

The lack of social connections presents an added risk of premature death, and the existence of relationships provides a positive health effect.

Previous research from the same team found that the heightened risk of death from loneliness is the same as smoking 15 cigarettes a day and being an alcoholic.

They said are many things that help to subdue the effects of loneliness.

With the evolution of the internet, people can keep in contact over distances that they couldn't before.

However, the superficiality of some online experiences may miss emotional context and depth.

A 2013 study, also from Brigham Young University, found that couples who text each other too much are less happy with their relationships, and it is better to have important conversations face to face.

The authors of that texting study note, however, that saying something sweet or kind in a text is universally beneficial.

The new study appears in Perspectives on Psychological Science.