Eating a bedtime protein shake with casein doesn’t seem to change how many calories your body burns at rest if you're a healthy older adult — at least according to one small study.

If you're a young adult who's overweight or obese, having a casein protein shake before bed doesn't seem to change your metabolism or fat burning in any clear way — it doesn't help or hurt much, based on the studies so far.

If healthy young adults drink a casein protein shake before bed, they might burn slightly less fat overnight than if they had whey protein—but about the same amount as if they had nothing at all.

If healthy guys drink a protein shake with 20-40 grams of casein right before bed, their bodies keep building muscle overnight — even if they worked out earlier in the day.

When older guys drink a protein shake with 40 grams of casein right before bed, about half of that protein shows up in their blood overnight — meaning their bodies are good at digesting and using it while they sleep.

If you eat a scoop or two of casein protein before bed, it probably won’t change how hungry or full you feel the next day — at least for healthy young or active older people.