I suppose "an alternative" is a bit subjective, but you have to realize that even ignoring the psychological barriers of a low-carb diet there are still some people that metabolically respond poorly to a low-carb diet.
My father is in his mid 50s, non-diabetic, runs marathons, and is in all-around excellent shape. He decided to give the low-carb approach a try just because I do it and because it interested him. For about a month he had no issues, was in ketosis, and our diets were nearly identical. Then, he started having issues on some of his runs: heart palpitations, severe loss of energy, etc. He actually told me he thought he was having a mild heart attack. Unfortunately, this happened a second time. He reverted back to his normal diet which includes a moderate amount of carbs, and hasn't had issues since.
Of course, I realize an n=1 anecdote proves nothing, but there are a fair number of respected doctors (who promote low-carb living) that also note that the diet doesn't work for everyone (citing similar issues to what my father experienced).