The general rule of thumb to maintain a metabolic fast is to keep your calorie intake at 25 calories or less within a 3-hour period. Generally, intake of foods, drinks, or supplements greater than this guideline will result in an insulin response and break your fast. SIGNAL contains only 25 calories, which falls perfectly within this guideline, so it provides crucial support for electrolyte balance and nitric oxide production during your fasting window without disrupting your metabolic state.