This leptitox will happen in extended leptitox fasts too. When there is no food, insulin levels stay low while the liver releases some of its stored sugar and fat. This is natural and not a bad thing at all. The magnitude of the spike will decrease as the liver becomes less bloated with sugar and fat. Who Should Not Do Intermittent Fasting? Women who want to get pregnant, are pregnant, or are breastfeeding. Those who are malnourished or underweight. Children under 18 years of age and elders. Those who instant keto have gout. Those who have reflux disease (GERD).