Question: why do you lose weight quickly on a low carb diet?
Answer: When you cut carbs, you reduce insulin and your kidneys start shedding excess water ( 11 , 12). It's common for people to lose a lot of water weight in the first few days on a low carb diet. Some dietitians suggest you might lose up to 5–10 pounds (2.3–4.5 kg) this way.