When I was starting out with OMAD, the first 3-4 days where the hardest because my body was accustomed to eating regular daily meals and snacks and then suddenly, I was eating only one meal a day. On my first 2 days, my tummy was making sounds, it's like telling me that it needs food also when I'm nearing the 24 hour eating schedule, I did have dizzy spells and felt weak but over the next several days, I got used to it and my body clock adjusted to a single meal.