Intermittent fasting (IF) is an eating pattern that cycles between periods of eating and voluntary fasting, used to achieve specific metabolic goals. The goal of a fast is to maintain a low insulin state, allowing the body to shift its fuel source from consumed glucose to stored body fat, often leading to ketosis. Practitioners often worry whether external factors, including the act of crying, could compromise this metabolic balance.
The Caloric Profile of Tears
Tears are a complex fluid, but their composition means they contain virtually no caloric energy. They are composed of nearly 98% water, which, like pure water, is non-caloric and cannot break a fast. The remaining components are a mixture of electrolytes, such as sodium and potassium, along with small amounts of proteins, lipids, and mucins.
The proteins and fatty oils present in tears are in such minute amounts that they do not register as a meaningful energy source. The physical substance of the tears themselves does not supply enough caloric energy to interrupt the fasted state or cause a measurable insulin spike. The focus must shift to the body’s physiological reaction to the emotional event.
Hormonal Stressors and Metabolic State
The metabolic question surrounding crying relates not to the tears but to the emotional stress that triggers them. Crying in response to stress or sadness activates the body’s sympathetic nervous system, the “fight or flight” response. This activation results in the release of stress hormones, particularly cortisol and adrenaline (epinephrine).
Elevated cortisol levels have a direct impact on the body’s glucose metabolism, even during fasting. Cortisol is known to stimulate a process in the liver called gluconeogenesis, which is the creation of new glucose from non-carbohydrate sources like amino acids and glycerol. Studies involving high-dose cortisol infusions have shown that the hormone increases overall glucose production in fasted humans by significantly enhancing this gluconeogenic pathway.
This resulting increase in blood glucose is a natural, temporary metabolic disruption caused by the body’s stress response, not by ingested calories. While this endogenous glucose release can temporarily raise blood sugar and potentially inhibit deeper fasting benefits like autophagy, it is not considered “breaking the fast” in the conventional sense of consuming food. The hormonal spike is a transient internal reaction that dissipates once the acute emotional distress passes.
Practical Impact of Ingested Fluids
A crying episode often involves swallowing more than just tears, as fluids drain from the tear ducts into the nasal cavity. This means a person may also ingest small amounts of nasal mucus and saliva. Similar to tears, these fluids are predominantly water and contain negligible caloric content.
Saliva contains a small amount of the enzyme amylase, which begins the process of carbohydrate digestion, along with trace amounts of glucose and protein. Nasal mucus is mainly water and mucins, which are large, non-digestible protein molecules. The volume of these fluids ingested during a typical crying spell is very small, and the negligible caloric load is insufficient to stimulate a significant digestive or metabolic response that would end the fast.