There is no substitutes for “carbs” when you are competing in long distance bicycle racing. You still need fat and protein but you cannot digest or process them fast enough to provide the amount of energy you need during competition. And after you have depleted your glycogen stores they are replenished most efficiently with carbohydrates consumed as soon as possible after your effort.
I have never used the term “essential carbs” that I recall. What I would remind people of again is that a healthy gut biome is made up of a wide variety of bacteria. If you essentially cut out an entire food group it will have a negative effect on the diversity of these healthy bacteria. People have survived on meager diets made up of foods that have not provided a good variety of nutrients. Many go on for years eating what most would consider to be lacking in nutrients. But it still probably is not very good for them.
As far as the Atkins diet goes... I have had friends who have lost their health and died while refusing to give it up against their physician's advice. They all presumed that the self help diet books they read made them more qualified than the medical professionals who were trying to restore their health. I saw the same situation on many medical calls that we responded to.
There is nothing more stupid than putting your health at risk by falling for the nonsense from diet charlatans. And the biggest diet charlatan of the past three or so decades was Robert Atkins whose nonsense has likely compromised the health of millions.
Plenty of full blood panels and lost weight show that those people are wrong. That includes my own.
The fourth phase of Atkins goes to 100 net carbs a day. Not exactly “low carb.”
The ADA knew in 2006 that low carb actually fixed diabetes, but said that because a low carb diet was not as easy as eating pasta, they couldn’t recommend it:
https://www.webmd.com/diabetes/news/20060616/do-low-carb-diets-help-diabetes
Now, 13 years later, the ADA gladly admits low carb is a provably excellent way to live a long life:
https://www.diabetesdaily.com/blog/very-low-carbohydrate-diets-for-diabetes-ada-2018-580309/
The main UK Diabetes group has this now on their website, while the ADA is still “introducing” people to their newfound stance: