The question of whether Conjugated Linoleic Acid (CLA) breaks a fast is common for those practicing intermittent fasting (IF). Intermittent fasting involves alternating periods of eating and not eating, aiming to leverage the body’s metabolic shift during the fasting window. CLA is a naturally occurring fatty acid, often taken as a supplement, which introduces caloric and metabolic considerations. Determining if CLA interferes requires understanding the specific physiological changes sought through fasting.
Defining the Metabolic Threshold: What Actually Breaks a Fast
For many people, the primary objective of intermittent fasting is to promote a metabolic shift away from using glucose as a fuel source. This shift requires keeping insulin levels low, as insulin signals the body to store energy and halts the process of tapping into stored body fat. Therefore, a fast is typically considered “broken” when caloric intake is sufficient to cause a significant insulin release.
Many fasting protocols adopt the practical “50-calorie rule.” This guideline suggests that consuming fewer than 50 calories during the fasting window will not meaningfully disrupt the metabolic benefits. While any calorie intake deviates from a zero-calorie fast, this threshold is accepted as being too small to trigger a substantial insulin response. The emphasis is on maintaining the low-insulin state, which is the true marker of a metabolically effective fast.
Analyzing CLA: Caloric Content and Insulin Response
Conjugated Linoleic Acid (CLA), typically derived from safflower or sunflower oil for supplements, is a fat. As a fat, it provides nine calories per gram. A common supplemental dose of CLA ranges from 1 to 3 grams per serving, equating to approximately 9 to 27 calories. This caloric load generally falls well below the accepted 50-calorie threshold for breaking a fast.
The more significant consideration is CLA’s effect on insulin. Since CLA is a fatty acid, its consumption does not stimulate a large insulin spike, unlike carbohydrates or protein. Fat is considered non-insulinogenic, meaning it has a minimal impact on the insulin levels targeted by intermittent fasting.
However, some research, particularly in individuals with type 2 diabetes, suggests CLA supplementation may increase fasting glucose or reduce insulin sensitivity. For a healthy individual, a standard dose of CLA technically adds calories but is not considered an insulin-spiking agent that would break the metabolic benefits. The practical answer is that CLA generally maintains the low-insulin environment, though it violates a strict zero-calorie fast.
CLA and Deeper Fasting Goals: Autophagy and Ketosis
The effects of CLA become more nuanced when considering the deeper benefits of fasting, such as autophagy and ketosis. Autophagy is a natural recycling process where the body breaks down and reuses old or damaged cell components. This process is highly sensitive to nutrient availability and is primarily activated by a lack of nutrients, which inhibits the cell-growth signaling pathway known as mTOR.
Introducing any external fuel source, even a non-insulinogenic one like CLA, provides the body with immediate energy. This availability of new fatty acids may act as a nutrient signal, potentially slowing the cellular stress that drives autophagy. For those seeking maximum autophagy benefits, even a small caloric intake from fat may reduce the intensity or speed of this process.
Similarly, CLA does not inhibit ketosis by spiking insulin, but consuming it provides the body with an immediate source of fat to burn. This may slow the body’s reliance on its own stored body fat (lipolysis) for fuel, as the body preferentially uses the recently consumed CLA. Therefore, if the goal is to maximize the burning of stored fat or fully activate cellular recycling, the addition of CLA may be counterproductive by providing an alternative fuel source.