What’s Really Happening When You’re in Ketosis? Scientists Just Found a THIRD Answer!

I’ve always been curious about what’s really going on when we fast or go keto—not just the diet hype, but the actual chemistry. The ketogenic diet and intermittent fasting have been everywhere lately, with promises ranging from rapid fat-burning to better brain health. Ketosis—the state where your body runs on fat instead of carbs—is having a major metabolites moment.

As I dug into the research, I kept coming back to one big question: Do we actually understand what’s happening when we’re in ketosis?

Apparently, not quite. A group of researchers just uncovered something entirely new—a third metabolic pathway involving ketones that might explain some of the more mysterious effects of going keto, like appetite suppression and weight loss. And no, it’s not just about willpower or eating fewer muffins.

Here’s what they found:

The Known Story of Ketosis—Up Till Now

When your body runs low on glucose (say, after a day of fasting or sticking to a low-carb diet), it shifts gears and starts breaking down fat. This produces ketone bodies—mainly beta-hydroxybutyrate (BHB)—which act as an alternative fuel source.

That’s been the basic roadmap for decades. But Jonathan Long, a researcher at Stanford Medicine, and Yong Xu at Baylor College of Medicine, weren’t convinced that told the whole story.

So they decided to look closer—not at the diets or the outcomes, but at the molecules themselves. What was BHB really doing in the body?

Meet the Shunt Pathway, a Metabolites Highways

Their answer? A brand-new detour on the metabolic map.

In studies involving mice and humans, the team discovered a previously unknown route they call a “shunt pathway.” Here, BHB doesn’t just go straight to the burn pile—it gets attached to amino acids, forming a family of new compounds they’ve dubbed BHB-amino acids.

If the usual pathways are metabolic highways, this one’s a side road. But it turns out that detour might lead somewhere really interesting.

So… What Does That Have to Do with Appetite?

Here’s where things get cool.

People in ketosis often report that they’re just not as hungry. (If you’ve ever done intermittent fasting and suddenly realized you forgot to eat lunch, you know what I’m talking about.)

The researchers noticed that these new BHB-amino acids looked a lot like another molecule they’d studied called Lac-Phe, which is produced after intense exercise and is known to suppress appetite.

That resemblance wasn’t just cosmetic. The experiments showed that these new ketone-linked compounds actively reduced feeding behavior and promoted weight loss in test subjects. Suddenly, that “I’m weirdly not hungry” feeling in ketosis had a plausible, chemical explanation.

Why This Matters (Hint: It’s Bigger Than Diets)

This finding doesn’t just explain a keto quirk—it potentially rewrites how we think about the metabolic effects of fasting and fat-burning.

It also gives researchers a new way to explore ketosis’s known benefits, like seizure control in drug-resistant epilepsy. That’s right—the keto diet is a proven therapy for epilepsy, but we’ve never fully understood why it works.

Now, with these new metabolites in the picture, Long and his collaborators are going back to that question. They’re investigating whether this third pathway might be part of the therapeutic effect—and whether it could lead to new treatments that deliver those benefits without the extreme dietary restrictions.

The Bottom Line for Metabolites

We used to think we had ketosis more or less figured out. Burn fat, make ketones, use ketones, done.

Turns out, that was only part of the picture.

With this newly discovered metabolic off-ramp, we might finally have the tools to understand not just how ketosis works, but why it might help with things like appetite control, weight loss, and even neurological disorders.

It’s early days yet, but the map of metabolism just got more interesting—and a lot more promising!

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