Eating too much fast food, processed meat and cakes is putting people at increased risk of depression, according to a new study. 

Researchers at Manchester Metropolitan University's Bioscience Research Centre examined 11 studies into depression and inflammatory diets, covering over 100,000 people aged 16-72 across the US, Australia, Europe and the Middle East. 

Their analysis found that people with more inflammatory diets that were high in cholestoral, saturated fats and carbohydrates were 40 per cent more likely to develop depression. 

The higher risk factor was also consistent across age groups and prevalent in both men and women. 

One of the study's authors Study, Dr Steven Bradburn said: 'These results have tremendous clinical potential for the treatment of depression, and if it holds true, other diseases such as Alzheimer's which also have an underlying inflammatory component.

'Simply changing what we eat may be a cheaper alternative to pharmacological interventions, which often come with side-effects.

'This work builds on recent advances in the field by others, including the first ever clinical trial into dietary interventions for treating depression, which have shown beneficial improvements in depressive symptoms.

'It should be stressed, however, that our findings are an association, rather than causality. Further work is needed to confirm the efficacy of modulating dietary patterns in treating depression with relation to inflammation.' 

Researchers at University College, London, have also established a link between diet and depression. 

They said there was 'compelling' evidence that eating a Mediterranean diet rich in fish, vegetables, nuts and olive oil could lower the risk of developing depression by up to a third.  Unlike the junk diet, the Mediterranean diet is anti-inflammatory, containing less unsaturated fat and higher quantities of fibre and vitamin A, C and D. 

The study found that strict followers of the Mediterranean diet were a third less likely to suffer from depression than those who were not strict adherents, and that conversely, those who ate more saturated fat, sugar and processed food were at greater risk of depression. 

Study co-author Dr Tasnime Akbaraly said the evidence supported the inclusion of dietary counselling in treating depression. 

'Our study findings support routine dietary counselling as part of a doctor's office visit, especially with mental health practitioners,' she said. 

'This is of importance at a patient's level, but also at public health level, especially in a context where poor diet is now recognised to be the leading cause of early death across middle and high-income countries and at the same time mental disorders as the leading cause of disability.'