CLO is a popular supplement derived from Atlantic cod, valued primarily for its high content of Omega-3 fatty acids and fat-soluble vitamins A and D. For individuals practicing intermittent fasting, whether this oil can be consumed during a fasted state is a common dilemma. The answer depends less on the supplement itself and more on the specific metabolic goal of the fast.
Nutritional Profile of Cod Liver Oil
A standard serving of cod liver oil, typically one teaspoon, contains a small but notable caloric value. This single teaspoon provides approximately 40 to 45 calories, making it a source of energy that technically introduces nutrients into the body during a fast. The macronutrient breakdown is straightforward: it is composed almost entirely of fat, with negligible amounts of protein or carbohydrates.
The oil is rich in monounsaturated, saturated, and polyunsaturated fatty acids, including the potent Omega-3s, EPA and DHA. Beyond its fat content, CLO is a concentrated source of Vitamin A and Vitamin D, which supports bone health and immune function.
Defining the Metabolic State of Fasting
Fasting is not a single state but rather a metabolic continuum, and whether a fast is “broken” depends on the goal of the individual. The three primary objectives of fasting are: maintaining a state of caloric restriction, achieving deep insulin suppression to promote fat-burning (ketosis), and stimulating cellular cleanup (autophagy). Consuming any food or drink that significantly interferes with these processes is considered breaking the fast.
Insulin suppression is a primary goal for many fasters, as low insulin levels signal the body to shift from burning glucose to burning stored fat. Carbohydrates and protein are the most potent stimulators of insulin release, while pure fats typically elicit only a minimal insulin response. The other significant goal is autophagy, a cellular recycling process, which is primarily triggered by nutrient deprivation and the subsequent suppression of a growth-regulating pathway called the mammalian target of rapamycin (mTOR).
The Impact of Cod Liver Oil on Fasting Goals
Applying the nutritional facts of cod liver oil to the metabolic rules of fasting yields an answer that hinges on the individual’s priority. For those whose main goal is promoting ketosis and maximizing fat burning, a small dose of CLO is generally considered acceptable. Because the oil is pure fat with no carbohydrates or protein, it does not cause a significant spike in blood sugar or insulin levels. The body remains in a fat-burning state, as the hormonal environment required for ketosis is largely undisturbed by the small influx of dietary fat.
The situation changes when the goal is to maximize the cellular recycling process of autophagy. Autophagy is highly sensitive to the presence of any calories and, more specifically, to the activation of the mTOR pathway. Since one teaspoon of cod liver oil contains 40 to 45 calories, this caloric intake is sufficient to signal a temporary state of nutrient availability to the cell. Consequently, the consumption of CLO will interrupt the deepest level of autophagy signaling, even if it does not raise insulin. Therefore, while CLO does not necessarily break a fast focused on fat burning, it technically will break a fast centered on maximum cellular repair.
Strategic Timing and Supplementation
For those who choose to incorporate cod liver oil while fasting, strategic timing can help minimize metabolic interference. If the main objective is fat-burning and insulin control, taking a single, minimal dose of CLO is unlikely to derail the process. However, to ensure optimal absorption of the fat-soluble vitamins (A and D) and the Omega-3 fatty acids, it is often recommended to consume the oil alongside a meal containing other fats.
A practical approach is to schedule the cod liver oil intake to coincide with the beginning of the eating window. This timing ensures that the caloric load is introduced when the fast is intentionally broken, maximizing nutrient absorption while completely preserving the fasted state. Whether choosing liquid oil or capsules, the dosage should be kept within the standard recommendation to avoid a larger caloric impact that could inadvertently trigger an insulin response.