Protein keeps your hard-earned muscles happy, your stomach from growling an hour after you eat, and your metabolism humming at a fiery pace. But just like other really good things, getting tons and tons of extra protein isn’t always better. Here, five weird ways your body can go haywire when you start eating insane amounts of protein. (Not sure if you’re overdoing it? Use this tool to ballpark what a good amount of protein is for your body and lifestyle.)
When you cut your carbs to the bare minimum (which you’re likely doing if you’re on a super-high-protein diet), your body enters a state called ketosis, where it starts burning fat for fuel instead of the usual carbohydrates. Which might be great for weight loss, but not so much for your breath, said registered dietician Jessica Cording. That’s because when your body burns fat, it also produces chemicals called ketones that can leave your mouth smelling sort of like you drank nail polish remover. The worst part? Since the stench is coming from inside you, brushing, flossing, or rinsing won’t make much of a difference.
2. Your mood takes a dive
Maybe the Hulk-size bodybuilders at the gym are grunting because they’re working crazy hard. Or maybe they’re just in a crappy mood. Your brain needs carbs in all their sugary, starchy glory to stimulate the production of the mood-regulating hormone serotonin. Strip them from your diet, and you’re more likely to feel grouchy, irritable, or just blah. And yes, science backs this up: One Australian study of overweight adults found that those who followed a strict low-carb diet for a year reported more crankiness compared to those who followed a higher-carb, low-fat diet—even though both groups lost roughly the same amount of weight.