An extreme form of low-carbohydrate diet – the ketogenic diet – is established as a medical diet for treating epilepsy. Through celebrity endorsement it has become a popular weight-loss fad diet, but there is no evidence of any distinctive benefit for this purpose, and it had a number of side effects. The British Dietetic Association named it one of the "top 5 worst celeb diets to avoid in 2018".
Regarding VLCK diets, there is still some distrust in their usage, despite the solid scientific evidence that supports the use of this kind of diet as a useful weight-loss therapy [13,14]. This type of diet is characterized by the restriction of carbohydrates and/or caloric intake to the point of inducing a shift in metabolism and the production of plasma ketone bodies [15,16,17]. However, it was evidenced that a VLCK diet is safe because it does not modify the acid-base equilibrium . In fact, it has been proposed that the ketone body, β-hydroxy-butyrate (β-OHB) has several beneficial effects on metabolism  and psychological functions [20,21]. Nevertheless, a scarcity of studies has evaluated the effect of a VLCK diet combined with physical activity, on potential improvement in the psychological conditions and well-being of treated overweight/obese patients.
The average daily goal for keto is 20 grams of net carbs. Net carbs are the total carbs in a given serving of food, minus the carbohydrates that are supplied by fiber. You’ll find carb grams quickly add up, even when you’re choosing the best low-carb foods, like spinach and avocado. Keeping your body in a quasi-keto state can be hard on you, warns Santo: “This will leave you feeling sluggish, foggy, and discouraged,” he says. “It will most likely cause a weight plateau, and maybe even weight gain.” Here’s what it’s really like to be on a keto diet.
There are vegetables that are high in carbs and others low in carbs. The keto diet recommends sticking to the ones low on carbs but encourages you to eat a lot of them. Best vegetables are all green ones to make it easy. And vegetables that grow above the ground (e.g. lettuce) are always better than the ones that grow below the ground (e.g. potatoes)