Fasting symptoms like headache, lethargy, lack of focus, and irritability are withdrawal symptoms from regular meal dosing, not true hunger.

“The idea that somehow fasting is miserable was because people are responding to regularly dosing their body with meals. And in the anticipatory habitual stuff that's going on, and what do they get? There's symptoms of hunger: headache, lethargy, lack of focus, irritability. What happens when you give up cigarettes? Lack of focus, irritability, headache, shaky... Heroin, alcohol, and I'm not saying that food is addictive in that way. I'm saying the body only knows withdrawal when you're regularly dosing it all the time with stuff. So, all of what you feel, what you feel now is hunger really isn't hunger.”