Ghrelin is often called the "hunger hormone," and the name fits. It's produced mainly by your stomach, and it rises when you haven't eaten in a while — a built-in alarm clock telling your brain it's time to find food.
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​Here's the part that trips people up during a diet: ghrelin doesn't just respond to your last meal, it responds to sustained calorie restriction. When you lose weight, ghrelin rises as your body tries to defend its previous weight and restore fat stores. This is a huge, underappreciated reason dieting gets harder over time rather than easier — it's not just in your head. Your hunger hormone is measurably higher.
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​Poor sleep and high stress also push ghrelin up, which is why a rough week can leave you reaching for food even when your schedule hasn't changed.
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​The good news: eating enough protein blunts ghrelin more effectively than many other strategies, and ghrelin's rise after weight loss, while real, is a known and manageable part of the process rather than a sign that something is wrong with you.