Starvation
Starving to death is one of the worst ways to go, and it’s one of the most difficult ways to die. Over millions of years, the body has evolved to weather periods of fest and famine and will make adjustments to your metabolism to suit your external conditions. When your body is faced with starvation (as you learned with every diet imaginable), your body starts to burn through its fat stores for energy. When that runs out, you start to burn muscle.
After that, it gets worse. Your body needs to burn something, and you’re lacking in nutrients and vitamins. So between the two, your body is vulnerable to disease, which is a preferable way to go, compared to the alternative. If infection doesn’t get you, then you face a period of fatigue and listlessness due to insufficient electrolyte levels, then once all your muscles, fat and organs have been cannibalized, your body will go after your heart. Cardiac arrest follows.
It’s a brutal cycle of your body eating itself to keep you alive, but it’s that act that dooms you.