The Obesity Health Alliance estimates that around 40 million adults in the UK will be overweight or obese by 2035, which could result in more than 7.6 million new cases of disease.
Experts predict this will cause an additional 4.62 million cases of Type 2 diabetes, 1.63 million cases of coronary heart disease and 670,000 new cases of cancer.
They have now called on the government to introduce a strong childhood obesity strategy to combat the growing crisis.
According to experts, even the smallest of changes could make a massive difference to public health.
A 1% shift in the number of people putting on extra weight each year until 2035 could avoid around 77,000 cases of disease including 45,000 cases of Type 2 diabetes in the year 2035 alone.
Alison Cox, Cancer Research UK’s director of prevention and member of the Obesity Health Alliance, said: "These numbers are shocking and it’s difficult to think of the impact this will have on public health and an already strained NHS.
"Without bold action, the next generation will face more disease and live shorter lives.
"Kids are bombarded with advertisements for unhealthy food and if we are to give our children the chance for better and healthier lives, it’s vital the government’s childhood obesity strategy restricts this kind of marketing."
To tackle the obesity epidemic, the Obesity Health Alliance is calling on the government to introduce a strong childhood obesity strategy without delay.
They said it must include restricting junk food advertising on TV before the 9pm watershed, tightening online marketing to align with broadcast regulations, as well as setting targets for industry to reduce the amount of sugar and fat in food.
Modi Mwatsama, director of policy and global health at the UK Health Forum and member of the Obesity Health Alliance, said: "This study is a wakeup call for the government and shows a daunting future if no strong action is taken against the obesity epidemic.
“We can’t expect industry to make changes on their own and people need help making healthier choices.
"The government must lead the way by creating a level playing field with independent, regulated targets for reducing the amount of sugar, fat and salt in food.
"Without government action, our children face a life of disease and early death."