Public Health England revealed the boroughs stand above the national average of 88 outlets per 100,000 residents.
The government agency counted more than 8,600 fast food outlets in London such as burger, kebab, chip and sandwich shops.
Public Health England’s Dr Yvonne Doyle, director for London, said: “More than a fifth of adults and children eat takeaway meals at home more than once a week and we are experiencing a national obesity epidemic.
"It is particularly worrying that so many of London’s children are affected.”
The report comes at a time when local authorities and the government have made tackling childhood obesity a priority.
The government launched their Childhood Obesity Plan this August.
As part of the initiative, Public Health England is working with restaurants, cafés and fast food outlets to reduce the amount of sugar, saturated fat, salt and calories in products and increase healthier options.
London councils have joined various initiatives, including the Great Weight Debate, which crowd-sources ideas from Londoners on how children can live healthier lifestyles.
Borough councils such as Brent and even Westminster have also capped the number of planning permissions for fast food vendors near schools.
Brent’s Councillor Krupesh Hirani, cabinet member for community wellbeing, said: “The links between obesity and fast-food have been widely recognised in Brent.”
He said the council conducted its own “Check your chips” study in July.
The council had a mystery shopper visit 23 local takeaways close to secondary schools and purchase chip portions for sampling .
The findings showed a significant number of takeaways close to schools in Brent, particularly in deprived areas, and that secondary school students are more likely to consume takeaways if their school is within 400m of outlets.
Councillor Hirani said: “The results are cause for concern. We want to work with existing fast food outlets in Brent to get them preparing, cooking and promoting their food with a healthier customer in mind.”
But not all boroughs are saturated with fast food.
The map places west London boroughs such as Ealing, Hounslow, Harrow, Hillingdon and Kensington & Chelsea below the national average.
Councillor Hitesh Tailor, Ealing Council’s cabinet member for health and adults’ services, said: “Tackling obesity and helping people to maintain a healthy weight is a priority for the council and its partners.
"Being overweight will have an impact on health, increasing the risk of serious illnesses such as heart disease, cancer and type two diabetes.”
Ealing Council banned new hot food takeaways within a ten minute walk of existing schools in 2013.
Public Health England’s Dr Doyle added: “We need to do more and faster. Our environment makes it harder for families to make healthy choices.”
Reacting to the report, a McDonald's spokesman said: "There are a number of contributing factors behind obesity, from less active lifestyles to the food we all choose to eat.
"It is misleading to try and attribute it to a single company or factor.”
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