Unemployed obese people will have to diet or else lose their benefits, under new Tory proposals.
Alcoholics, drug addicts and others with “treatable conditions” could also face being stripped of their sickness payments.
UK prime minister David Cameron said it was "not fair" that taxpayers were being asked to fund welfare for those who refused help.
Around 100,000 people with conditions that fall under the new proposals are receiving sickness benefits and there is currently no requirement for them to undertake treatment.
The prime minister said: “Too many people are stuck on sickness benefits because of issues that could be addressed but instead are not.
“Some have drug or alcohol problems, but refuse treatment. In other cases people have problems with their weight that could be addressed, but instead a life on benefits rather than work becomes the choice.
“It is not fair to ask hard-working taxpayers to fund the benefits of people who refuse to accept the support and treatment that could help them get back to a life of work.
"The next Conservative government is determined to make sure that the hardest to help get the support they need to get them back to a fulfilling life. That is why I have asked Professor Dame Carol Black to undertake a rapid review in to how best to support those suffering from long-term yet treatable conditions back in to work.
“In particular, I have asked her to consider whether people should face the threat of a reduction in benefits if they refuse to engage with a recommended treatment plan - it is vital that people who would benefit from treatment get the medical help they need.”
Dame Carol Black, an advisor to the British department of health, said: “I am deeply interested in trying to overcome the challenges these types of benefit claimants pose.
‘Blanket ruling’ criticised
Susannah Gilbert, of obesity support group Big Matters, said a “blanket ruling” stripping people of sickness benefits would not work.
"I think it's naive to think people don't want to change their lives. Most people aren't happy with their weight and would like to change," she told the BBC Radio 4 Today programme.
Ms Gilbert said Westminster Council had tried a scheme to force obese people to go to gyms or have benefits cut, but eventually decided it was not "feasible".
Conservative minister for the disabled Mark Harper stressed that the party was still investigating how the idea would work.
“It’s about how we get people to engage with the treatments that are available.”
PA