If Jehovah's Witnesses aren't allowed to smoke why is it ok for them to eat such things as hydrogenated oils?

The Watchtower Society uses the reasoning that the bible says to rid oneself of ALL defilement of the flesh and, ones body is their temple in order to enforce their ban on smoking because it has been proven to cause health problems. Why, then, does the Watchtower Society allow JWs to consume such things as partially hydrogenated oils, red meat, processed (white) sugar, processed (white) flower, saturated fat and many, many other ingredients common in Western diet that have likewise been proven to cause serious health problems in humans, even when consumed in small quantities? I've never heard of any one of JWs being disfellowshiped because they are obese (a glutton) although obesity has been proven to be the cause of countless health problems, not to mention also being one of the seven deadly sins mentioned in the bible. Keep in mind that it is entirely possible for one to smoke in complete isolation from others so as not to cause harm in any way to anyone but oneself in the same sense that an obese individual harms only them self by habitually overindulging in (unhealthy) food. Is it not reasonable for intelligent persons then to regard these things, namely smoking and the eating/over-eating of food proven to cause disease, as equally sinful in the eyes of Jehovah? Please explain why they are not treated as such under the direction of the Watchtower Society.