Penny Williams from Diabetes UK replies: The theory behind the low carb/high protein diet is that obesity is the main cause of insulin resistance and that by cutting out carbs the insulin-based chain of events will be prevented. Weight loss, by any means, reduces the body's resistance to insulin. Carbohydrate is substituted for a diet that is high in protein and fat, which the body will use for energy. However, carbs are required to replace the body's glycogen supply, which is stored energy in the liver and muscle. Therefore, the initial rapid weight loss is due to the loss of water from the body's glycogen stores. This diet restricts important food groups, including fruit and vegetables, and causes short-term rapid weight loss which is not sustainable.
A side-effect of a low carbohydrate intake is the production of ketones, which cause the body to break down fat stores for energy. This can cause ketoacidosis, a condition that increases acidity in the blood, ie uncontrolled diabetes. Therefore it is not advised for a person with diabetes to follow this kind of diet.