Is Fasting Actually Good for You? What New Research on the Immune System Reveals
Fasting is often described as a simple way to improve metabolism and burn fat. But new research suggests the story is more complex than that.
A recent study discussed in Medscape highlights a surprising finding: under certain conditions, the immune system may actually slow fat breakdown, even during situations like fasting that are commonly associated with increased fat burning.¹
What the researchers were studying
This research was mechanistic, meaning it was designed to understand how biological systems work rather than to test lifestyle habits or health protocols. To study immune and metabolic signaling, researchers used fasting and cold exposure as experimental stressors. These conditions reliably activate stress responses in the body, which makes it easier to observe how different systems communicate with each other. In simple terms, fasting was used as a tool to trigger a response, not as a recommendation for better health or weight loss.
What they found
When the body experienced stress, including fasting, immune signaling increased in a way that appeared to reduce fat breakdown. Instead of encouraging the body to burn stored fat, the immune system sent signals that promoted energy conservation.
This response likely evolved as a protective mechanism. When the body senses uncertainty or stress, its priority shifts from efficiency to survival. Holding onto energy becomes more important than using it.
Does this mean fasting is bad for you?
Not necessarily. But it also does not mean fasting is automatically beneficial.
This study does not tell us who should fast, how long to fast, how often to fast, or whether fasting improves health outcomes in real world settings.
What it does show is that the body does not always respond to fasting by increasing fat burning, especially if fasting is experienced as a stressor.
Why this matters
Many wellness trends are built on the idea that adding stress to the body leads to better results. This research challenges that assumption. It suggests that stress, even when intentional, can trigger protective responses that work against the desired outcome.
This helps explain why fasting may feel helpful for some people and unhelpful for others. The metabolic response depends on context, including baseline health, sleep, nutrition, psychological stress, and immune activity.
The takeaway
This research helps explain why the body behaves the way it does under stress. It does not translate directly into lifestyle advice or universal recommendations.
So if you are asking, “Is fasting good for me?” the most evidence based answer right now is that the effects vary from person to person, and this study alone cannot answer that question.
What it clearly shows is that the body’s first priority under stress is protection, not fat loss.
Reference
Surprise Finding: Immune System May Keep Us From Burning Fat. Medscape. 2026.
