Following a very high-fat diet may be challenging to maintain. Possible symptoms of extreme carbohydrate restriction that may last days to weeks include hunger.
For adults following the ketogenic diet, the most common complications include weight loss, constipation and increased levels of cholesterol and triglycerides. Headaches can be a common side effect of switching to a ketogenic diet. They may occur as a result of consuming fewer carbohydrates, especially sugar. Ketosis can cause side effects such as bad breath, headache, fatigue and weakness. It's not clear what kind of possible long-term health risks a low-carb.