HOW LYME & CHRONIC INFECTIONS EFFECT HUNGER

“Feed a cold. Starve a fever.” The fact that infections can cause swings in our appetite is embedded in the common knowledge and shared wisdom of mainstream culture.

But why does that happen? What does eating have to do with fighting off a virus, bacteria, spirochete, worm or any other critter that’s trying to take up residence?

Most normal body functions are intimately connected with the immune system and our hunger system is no exception. The same physiology that we use on a typical, relaxed day can be repurposed for defense at any time. It’s an ingenious system honed over millions of years of evolution.

It turns out that we’re better at fighting off certain critters when we’ve eaten while for other types of infections, it’s better that we haven’t eaten anything. There’s also individual variability in terms of how you will respond - your body might choose a different strategy than your neighbor to combat the same critter.

A lot of different hormones are involved in adjusting appetite. But when an infection causes ravenous hunger that seems connected to blood sugar regulation, then almost certainly a hormone called ghrelin is involved.

Ghrelin is made in the stomach and signals the hypothalamus in the brain that we’re ready for chow time. It tends to rise before the times we typically eat so it can be adjusted based on our eating patterns.

When we’re sick, the body may choose to raise ghrelin as part of its pathogen fighting strategy. You can see in the diagram below that ghrlein increases Th2 lymphocytes while decreasing Th1 lymphocytes. Th1 responses are best for killing small parasites inside of cells. Th2 responses are more optimized for handling bigger critters that live outside of cells, such as borrelia and friends.

So while we can use strategies to reduce hunger and increase our feelings of fullness after eating, it’s important to go after the infection itself.