One third of the sum -- €398m -- is incurred via direct healthcare costs, such as hospital stays, GP consultations and drug costs to treat weight-related conditions such as cardiac disease, type 2 diabetes, cancer and strokes.
But a massive two thirds, or €728m, relates to the knock-on effect on businesses in Ireland.
Lower back pain is a major cause of absenteeism and productivity loss.
Martin Higgins, Safefood's chief executive, said the figures were just the tip of the iceberg.
"We now have reliable contemporary and locally relevant figures for the annual economic cost of weight-related ill health in Ireland," he said.
"While it is acknowledged that these are conservative figures and don't reflect the human and social costs, they show a compelling case for obesity prevention, based on changes in our food environment and activity levels."
Safefood's Dr Cliodhna Foley-Nolan said that the problem was a ticking time bomb for our health services.
"Excess body weight is associated with a significant burden of chronic disease, with negative effects on overall life expectancy, disability-free life expectancy, quality of life, healthcare costs and productivity," she said.
"The findings from this research are critical for establishing priorities in health policy development and to guide and inform our response to the issue of excess weight in our society, which is fundamentally preventable."
Professor Ivan Perry of University College Cork, who led the research, said that, although the Government and society have a role to play, individuals and food producers must also take responsibility.
"The current findings on the cost of overweight and obesity highlight the extent of societal involvement in diet and health and the limitations of approaches that emphasise the role of personal choice, responsibility and market forces in relation to diet and health," he said.
"The current obesity epidemic in children and adults represents a clear example of market failure with external/third party costs defaulting to taxpayers.
"The food sector is currently regulated to ensure food safety.
"Policy makers need to consider whether there is a need to extend this regulatory framework to address the effects of diet on health and wellbeing," he added.
The Safefood research, led by a team from UCC, found that overweight and obesity combined accounted for a similar burden of disease and cost in the Republic and in Northern Ireland.