This link might not work for some of you, but the Wall Street Journal has an interesting article on the challenge to produce a low or no-carb bread, which means no wheat or most other starches, making it a much harder challenge than gluten-free breads. A second challenge is the cost, a loaf can cost $10 or more.
This seems ridiculous. If you can't eat carbs why are you even looking at bread substitutes. Eat vegetables, and meat, and cheese, and eggs. Serious carb free diets couldn't have most ripe fruits due to sugar content which would be horrible.
I can't access the article, but from what is there before the "stop," the bread seems loaded with saturated fat.
It reminds me of some vegan recipes where the workaround is unhealthier than just eating the animal product. There are healthy vegan recipes, but attempts to make it like non-vegan usually fall flat.
I have more sympathy for those who have medical reasons why they cannot eat wheat bread or other foods than I do those who do so as a lifestyle choice, but don't want to give up their previously favorite foods. If you are eschewing meat, you shouldn't be chewing on plant burgers that have far more 'processed' ingredients in them.
Carbs are necessary as are fats and proteins, the trick is to eat them in reasonable proportions and quantities.