The reason you feel sick is because you're body isn't used to the shift from carbohydrates for energy and ketones as energy (body fat). You get brain fog becaus

The reason you feel sick is because you're body isn't used to the shift from carbohydrates for energy and ketones as energy (body fat). You get brain fog because only fat in the form of ketones can cross the blood brain barrier. So adaptation to ketones are vital. You need to work into it. No different from exercise, or climate adaptation. Having cold showers shifts your body into using ketones more and more. Regarding not eating breakfast, watch these videos from FoundMyFitness: Dr. Satchin Panda on Time-Restricted Feeding and Its Effects on Obesity, Muscle Mass and Heart Health https://www.youtube.com/watch?v=-R-eqJDQ2nU https://www.youtube.com/watch?v=-R-eqJDQ2nU Ruth Patterson, Ph.D. on Time-Restricted Eating in Humans & Breast Cancer Prevention https://www.youtube.com/watch?v=8qlrB84xp5g https://www.youtube.com/watch?v=8qlrB84xp5g Time restricted eating, AKA your 16/8, is VERY important. Even if you don't immediately notice changes. Those changes could begin to occur 2 to 8 years later. Depending on adherence. Also based on Dr. Ruth Patterson's advice, skipping breakfast leads to eating late into the night, which is not good for your health generally.