The number of takeaway outlets has significantly increased over the last 20 years, particularly in the poorest areas, and is likely to be a factor in why people living in such places are often overweight, a study has suggested.

The research, carried out at the University of Cambridge, analysed the number of takeaways across Norfolk between 1990 and 2008 and how this related to levels of neighbourhood socioeconomic deprivation.

It is well known that frequent dining on food from fish and chip shops, kebab shops, and Indian and Chinese takeaways is linked to weight gain over time, and previous studies have shown that people of low socioeconomic status and living in deprived areas are more likely to be overweight and consume unhealthy diets than other sectors of the population.

Research carried out by the university last year found that those that lived and worked near a high number of takeaway outlets tended to eat more takeaway food and were more likely to be obese than those less exposed.

The latest study, carried out at its Centre for Diet and Activity Research (CEDAR), found that socioeconomic differences in takeaway food outlet access might partially explain observed socioeconomic differences in diet and body weight.

Over the 18 year period, the number of takeaway food outlets in Norfolk rose by 45%, from 265 to 385 outlets.

This equated to an increase from 2.6 outlets to 3.8 outlets per 10,000 residents.

The highest absolute increase in density of outlets was in areas of highest deprivation, which saw an increase from 4.6 outlets to 6.5 outlets per 10,000 residents (a 43% increase).

In contrast, areas of least deprivation saw an increase from 1.6 to 2.1 per 10,000 residents over the time period (a 30% increase).

Researchers suggested local authorities should think about restricting the number of takeaway outlets in areas, particularly in more deprived places, in the light of their findings.

Lead author PhD student Eva Maguire said: "The link we've seen between the number of takeaway food outlets and area deprivation is consistent with other reports, but this is the first time the changes over time have been studied in the UK.

"There were differences in the densities of takeaway outlets as far back as we looked, but these differences also became more extreme."

Dr Pablo Monsivais, also from CEDAR, said: "The growing concentration of takeaway outlets in poorer areas might be reinforcing inequalities in diet and obesity, with unhealthy neighbourhoods making it more difficult to make healthy food choices.

"Our findings suggest that it might be time for local authorities to think hard about restrictions on the number and location of outlets in a given area, particularly deprived areas."

They said although the study was only carried out in Norfolk, the county was large and shared characteristics with other areas of the UK so the findings would be similar across the country.

The research was published in the journal Health & Place.