Is Intermittent Fasting Safe for Your Adrenals?
Summary
A common concern about intermittent fasting is that it stresses the adrenal glands by spiking cortisol. Dr. Berg explains that cortisol’s role in raising blood sugar during a fast is a normal, healthy adrenal function — not a sign of stress or damage. Rather than harming the adrenals, intermittent fasting is presented as a tool to address the root problem: insulin resistance.
Key Takeaways
- Cortisol spikes during fasting are normal — the adrenals are designed to raise blood sugar when levels drop too low
- Intermittent fasting does not inherently stress the adrenals; it is working with a natural physiological mechanism
- Insulin resistance causes elevated fasting insulin, which pushes blood sugar down and can create the symptoms people mistakenly blame on fasting itself
- Intermittent fasting is a tool to fix insulin resistance, not a cause of adrenal dysfunction
- If symptoms of low blood sugar appear during fasting, it may indicate the adrenals need additional support
- Adrenal support may be beneficial alongside intermittent fasting to help stabilize blood sugar levels
Details
Cortisol and Blood Sugar Regulation
When you fast, blood sugar can drop, triggering the adrenal glands to release cortisol. Cortisol’s job in this context is to raise blood sugar and counter hypoglycemia. Dr. Berg emphasizes this is an expected and appropriate adrenal response — comparable to how the adrenals release anti-inflammatory compounds in response to infection or injury. The adrenals are responding correctly, not being damaged.
The Real Culprit: Insulin Resistance
The more significant issue for people experiencing symptoms during fasting is insulin resistance. When insulin resistance is present:
- Fasting insulin levels remain elevated
- This chronically pushes blood sugar lower
- Symptoms that feel like adrenal stress may actually stem from unstable blood sugar driven by high insulin
In this context, intermittent fasting is framed as a corrective tool — by reducing meal frequency and lowering insulin exposure, it helps the body gradually restore insulin sensitivity.
When Adrenal Support May Be Needed
If someone is experiencing noticeable low blood sugar symptoms during intermittent fasting, Dr. Berg suggests that supporting the adrenal glands may help:
- Assist in stabilizing blood sugar levels
- Prevent blood sugar from dropping too low during fasting windows
- Allow the body to adapt more smoothly to the fasting protocol
No specific supplements or dosages are mentioned in this segment, but the recommendation is to address adrenal function as a complement to — not a reason to avoid — intermittent fasting.