The body will eventually adapt to a zero carb diet and aerobic endurance can be quite good if not superior, but you have to ask what the usefulness of such a diet is for you. Moderate amounts of carbs are not harmful, say up to 100 grams per day if you don't exercise, and more depending on how much cardio you do. Pure glucose (which is what starch ends up as) can be used by any cell in the body as opposed to fructose (50% of sugar) which must be processed by the liver. Best time to eat starches is before cardiovascular exercise because you'll burn a lot of them off before the body can even store them as fat.
We might be omnivores but yes most people eat too many carbohydrates and it's carbohydrates in excess that cause most health problems, especially if you combine carbohydrates with fats and overeat calories. Fat builds up in the liver and pancreas and leads to metabolic syndrome. This is especially so if you don't consume choline (found in eggs) or betane (found in whole wheat).. in that regard if you are going to eat carbs, whole wheat is probably the healthiest, and not rice, oats, or a ton of refined stuff. Or just take a choline bitartate supplement or eat eggs. Problem solved.
https://www.verywellfit.com/saturate...-carbs-2241606
You only need to look at what happens to dogs, cats, horses, and other animals when you feed them cheap, high carb foods.. health tends to suffer. Even livestock which are grass eaters suffer negative effects from low fiber refined carbs. People want to put the blinders on and pretends it's the fat that's the problem while they keep shoveling down the triscuits and eating their hot pockets and pizza. Portion size is very important when it comes to prediabetes or type 2 diabetes.. a whole dairy queen large blizzard is not really good for anyone but some people can genetically handle the sugar load better than others. A type 2 would likely spike above 300-400 with a large blizzard and such items are not advised.
Low carb reduces blood sugar and can "treat" type 2 diabetes but is not really a cure.. without removing the fat from the liver and pancreas you will not have any sort of cure. Lose weight, eat a lower carb diet, and get plenty of choline and betane while you are in a calorie deficit so your body targets the liver and organs when removing fat. Get a blood glucose tester (beware most of them on the market read 10-20 points higher than your actual, lab tested value).. the only tester I found to be really accurate is discontinued.. it was a "trueresult" meter.