A new "fat map" of the UK published today shows high levels of obesity in the Midlands, Wales, North East and parts of the South East.
The map, created by Dr Foster Research, suggests the problem may be getting worse when compared with a similar map published two years ago.
Although different methodology was used, researchers said the 2008 map is now revealing pockets of obesity in previously unexpected areas.
The data, from GP practices across the UK, shows that more than one in 10 patients registered with GPs in some parts of the country are obese.
Hotspots include Bexley Care Trust in London, where 9.1 per cent of patients registered with their GP are obese, Barking and Dagenham primary care trust (PCT) where 9.3 per cent are, and Medway PCT in Kent where 9.4 per cent are obese.
The Shetland Isles has the highest proportion, with 15.5 per cent of patients being obese, closely followed by many parts of Wales.
The North East has a similar problem, including Wakefield District PCT where 9.3 per cent of patients are obese, Doncaster PCT where 10.1 per cent of patients are obese and Barnsley PCT where 10.8 per cent of patients are obese.
The map and accompanying report were complied using data from GP practices relating to the Quality and Outcomes Framework (QOF) for 2006/07.
The QOF includes keeping a register of patients aged 16 and over with a body mass index (BMI) of 30 or over in the previous 15 months.
Alex Young, senior project manager at Dr Foster Research, said: "We need to wait a few more years before we can say definitely that things are getting worse but there does seem to be a growing problem in some areas.
"We are seeing parts of the outlying regions being affected rather than just urban areas.
"Urban areas might be dealing with the problem more effectively but in the outlying regions it seems to be getting worse - places like Newport, Plymouth, St Davids, Stockport.
"If you look at Liverpool, Sheffield and Bristol, the levels are low.
"In the outlying areas, health services are maybe less available. In a city, the services are better, such as local access to GPs.
"There's also a certain amount of social stigma attached to being obese, it may be that these obese people are not going to see their GP.
"However, we need to bear in mind that some PCTs are better at recording the data than others (which could affect the results)."
Government figures suggest that two-thirds of adults and a third of children are either overweight or obese in the UK.
This could rise to almost nine in 10 adults and two-thirds of children by 2050, putting them at serious risk of heart disease, diabetes and cancer.
Estimates from 2002 show that people who are overweight or obese cost the economy £7bn in treatment, benefits, loss of earnings and reduced productivity.
By 2050, this figure could be £50bn - almost half the NHS's yearly budget.
Dr Colin Waine, visiting professor at Sunderland University and chairman of the National Obesity Forum, said: "It is important that people understand both the dangers of obesity and the benefits to their health of losing weight.
"Even a modest reduction of 5-10 per cent of body weight leads to reduced blood pressure, a reduction in the risk of developing diabetes, a fall in obesity-related cancer deaths and a reduction in total mortality.
"We strongly urge anyone who might be at risk to see their GP who can advise them on weight loss options that are tailored to their needs."
A Department of Health spokeswoman said: "Earlier this year we published a £372m strategy to tackle obesity - recognition of the fact that it is the biggest health challenge we face.
"Over the last 60 years, the number of people who are severely overweight has risen steadily and there is a very real danger that today's children will not live longer than their parents.
"As part of the strategy, this autumn we will be launching a national movement that will bring about a fundamental change in the way we live our lives.
"The Change4Life movement will not hector or point the finger, it will give everyone - wherever they live - the information and support they need to eat more healthily and be more active.
"Government cannot do this alone, that is why we are inviting everyone - from multinational food companies to keep fit clubs in village halls - to join our movement and make England healthy."
Last night, the Tories said overweight people needed to face up to reality to conquer obesity and live healthily.
Shadow health secretary Andrew Lansley said it was time to "take away the excuses" so that overweight people started exercising and eating more fruit and vegetables.