The McKinsey Global Institute said obesity cost £1.3tn, or 2.8% of annual economic activity - it cost the UK £47bn.
The worldwide cost of obesity is about the same as smoking or armed conflict and greater than both alcoholism and climate change, research has suggested.
The McKinsey Global Institute said it cost £1.3tn, or 2.8% of annual economic activity - it cost the UK £47bn.
Some 2.1bn people - about 30% of the world's population - were overweight or obese, the researchers added.
They said measures that relied less on individual responsibility should be used to tackle the problem.
The report said there was a "steep economic toll", and the proportion could rise to almost half of the world's population by 2030.
The financial costs of obesity are growing - for health care and more widely in the economy. By causing illness, obesity results in working days and output lost.
The researchers argued that a range of ambitious policies needed to be considered and a systemic rather than piecemeal response was essential.
What is obesity?
The report said the right measures could save the UK's NHS £760m a year
A person is considered obese if they are very overweight with a high degree of body fat.
The most common way to assess if a person is obese is to check their body mass index (BMI), which divides your weight in kilograms by your height in metres squared.
If your BMI is above 25 you are overweight. A BMI of 30-40 is considered obese, while above 40 is very obese. A BMI of less than 18.5 is underweight.
"These initiatives would need to draw on interventions that rely less on individual responsibility and more on changes to the environment," the report said.
If the right measures were taken there could be long-term savings of £760m a year for the UK's National Health Service, it added.
The initiatives assessed in the report include portion control for some packaged food and the reformulation of fast and processed food.
It said these were more effective than taxes on high-fat and high-sugar products or public health campaigns. Weight management programmes and workplace fitness schemes were also considered.
The report concluded that "a strategy of sufficient scale is needed as obesity is now reaching crisis proportions".
The rising prevalence of obesity was driving the increase in heart and lung disease, diabetes and lifestyle-related cancers, it said.
Dr Alison Tedstone, chief nutritionist at Public Health England (PHE), said: "The report is a useful contribution to the obesity debate. PHE has consistently said that simple education messages alone are not enough to tackle obesity."
Dr Tedstone said obesity required action across national and local government, industry and society as a whole, and there was "no single silver bullet solution".
The report was produced by McKinsey Global Institute, the business and economics research arm of consultancy firm McKinsey & Company.