By Brian Harris, MD

When patients tell me they can't sleep, they usually expect me to ask about their phone use or their mattress. Those things matter, but in my clinic, we start with what you’re eating. As Dr. Robert Lustig has brilliantly argued in his work on metabolic health, processed sugar is a neurobiological disruptor that keeps your brain in a state of chemical "on."

The Insulin-Orexin Feedback Loop

Think of Orexin (also called hypocretin) as the brain's internal master switch for wakefulness. When we consume high-glycemic sugars, we trigger massive insulin spikes that temporarily suppress these neurons—giving you that post-lunch crash. But the real problem comes later: the "rebound" insomnia. When your blood sugar eventually bottom outs at 2:00 AM, your brain treats it as a survival crisis, waking you up in a panic.

Dopamine and the Reward Cycle

I also specialize in Addiction Medicine, and this is where the science gets really interesting. Sugar hits the same dopaminergic pathways as many addictive substances. This constant "reward" cycling keeps the brain wired and scanning for more, making it impossible to drift into the quiet, low-dopamine state required for deep N3 (Slow Wave) sleep. If your brain is busy chasing a sugar high, it isn't busy repairing your neurons.

The clinical takeaway: Fixing your sleep often requires fixing your metabolic signaling first. Reducing added sugar isn't just about weight—it's a critical clinical intervention to quiet the brain for rest.