Diet Pills & Breathalyzers Don’t Mix

The often publicized lives of celebrities can entertain us, annoy us, or make us wonder why it’s even news worthy at all. It can also teach us a thing or two. Hayley Hasselhoff, the daughter of Baywatch hero David Hasselhoff did just that. She recently filed a writ of mandate to set aside a driver license suspension stemming from a 2012 DUI arrest in Los Angeles. Hasselhoff, claiming she only had one alcoholic drink more than two hours prior to her breathalizyer test, also took the diet pill, Phentermine. This diet pill caused the breathalyzer to produce a false positive.

It turns out it’s all about the body’s use of energy. Generally, the body uses glucose for energy burning, received from carbohydrate ingestion. The body puts away any extra energy in the form of fat. Similar to low carbohydrate diets, diet pills cause the body to burn stored fat. When glucose levels get low the body converts these fatty acids into acids called ketones. Diet pills which cause the body to burn stored fat also create ketones. Extra ketones not used up by the body are released either in urine or through the lungs.

The ketone’s chemical composition, when released through the lungs, is akin to the chemical composition of isopropanol, a type of alcohol. The breathalyzer cannot distinguish between this type of alcohol and the type found in alcoholic beverages, ethyl alcohol.

In short, dieting and driving, while displaying other behaviors of intoxication, may lead to a DUI arrest.