Shetland and parts of Wales and northern England are Britain's obesity hotspots, according to a map of obesity rates compiled from GP records.
Almost one in four adults is obese and the rates are rising, according to official government figures.
The map, by analysts Dr Foster, is not a definitive measure of obesity, but reflects the fact that GPs are asked to record obesity only in new patients.
Shetland tops the list, followed by Torfaen, Blaenau Gwent and Neath.
The Dr Foster figures, which are broken down to a local health body level, are much lower, but that reflects the fact that GPs are only asked to record obesity in new patients.
The Shetland Islands has the worst rates with 15.5% of patients classed as obese.
Five places in Wales feature in the top six worst areas, with Barnsley in seventh place.
Dr Foster, which received funding from pharmaceutical firm Roche, the manufacturer of an obesity drug, to do the research, acknowledged not everyone was being picked up by the GP data.
Shetland - 15.5%
Torfaen - 13.9%
Blaenau Gwent - 12.5%
Neath - 11.9%
Caerphilly - 11.1%
Rhondda - 11.1
Barnsley - 10.8%
Wrexham - 10.8%
But Alex Young, senior project manager at Dr Foster, still said it was showing some unexpected results.
"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."
He pointed to areas outside the major cities such as Newport, Plymouth and Stockport which all had obesity rates above 7%.
The study also highlighted the health benefits of weight loss, saying a reduction of between 5% to 10% of body weight leads to a halving of the risk of diabetes and obesity-related cancer deaths.
But Dr Ian Campbell, medical director of Weight Concern, said the figures should not be seen as a definitive picture of obesity around Britain.
"What they show is the areas where GPs are picking this up and taking it most seriously."
And health chiefs on Shetland dismissed the research as "misleading and simplistic".