Without government interference, insurance markets will naturally charge higher premiums for riskier individuals. For example, life insurance premiums vary considerably based on factors that increase the likelihood of death, such as age, gender, smoking status, and health.
Under Obamacare, many factors that influence healthcare expenditures are excluded from premiums. For example, premiums make no distinction for obesity, likelihood of having a baby, alcoholism or pre-existing conditions. One notable exception is for smokers, where premiums may be up to 50 percent higher than that for non-smokers. I have collected data on premiums for smokers and non-smokers in 35 states, and the data shows large variation in the extent to which smokers are charged more for their choice.