When you eat less than 50 grams of carbs daily, your body eventually runs out of fuel (blood sugar) it can use quickly. This typically takes 3 to 4 days. Then you’ll start to break down protein and fat for energy, which can make you lose weight. This is called ketosis. It's important to note that the ketogenic diet is a short-term diet focused on weight loss rather than pursuing health benefits.
People use a ketogenic diet most often to lose weight, but it can help manage certain medical conditions, like epilepsy, too. It also may help people with heart disease, certain brain diseases, and even acne, but there needs to be more research in those areas.
A ketogenic diet may help you lose more weight in the first 3 to 6 months than some other diets. This may be because it takes more calories to change fat into energy than it does to change carbs into energy. It’s also possible that a high-fat, high-protein diet satisfies you more, so you eat less, but that hasn’t been proved yet.