Brace yourself for another hike in health insurance rates if you have a government-subsidized policy through the Affordable Care Act, also known as Obamacare. In Tennessee, premiums for 2018 will jump anywhere from 21 to 42 percent depending on your private sector carrier and your ZIP code, Michael Humphreys, assistant commissioner for insurance in the Tennessee Department of Commerce and Insurance, told The Rotary Club of McMinnville on Thursday.That increase comes on top of rates leaping upward of 44 to 62 percent in 2017 and 36 percent, as a statewide average, in 2016. A major factor in the exploding ACA premiums is the very poor health condition of many Tennesseans, Humphreys explained, noting the private insurance industry underestimated its future losses in the Volunteer State when the Federally Assisted Marketplace opened for business in 2010.“The overall health condition of the state — cancer, diabetes, obesity — didn’t justify the low initial rates,” Humphreys said.