This is probably one of the biggest element of confusion among people starting a low carb diet. First of all, the definition of “low carb” itself can be misleading, since you have strict low carb and liberal low carb.
Liberal low carb is a diet where the daily total carbohydrates content is between 50g and 100g per day, it’s pretty much the same content of carb in an average Italian diet before Maccas started opening joints in the Belpaese: espresso coffee for breakfast, 100g of pasta (70-80g of carbs) for lunch with meat and vegetables, just meat and vegetables for dinner.
Strict low carb is between 25 and 50g of carbs per day, while below that amount we enter the keto zone. Or not.
You see, the maximum amount of carbs for a person to stay in ketosis (a physiological state where our body utilize mostly ketones as source of energy) is highly variable, and even if there is general consensus that everyone eating less than 20g of carbs per day should be in ketosis, the upper limit depends on many factors and for some well keto adapted athletes can be even 50g per day for a few weeks in a row. Of course, if you are reading this you aren’t probably a keto athlete training for the next world champion, so let’s define keto as less than 25g of carbs per day.
So, it’s keto more efficient as a weight loss diet than low carb? Yes and no, it depends also on how much fat and proteins you are eating. You see, even if many on the net are trying to convince you that a calorie is not a calorie (and that’s true), a calorie is still a calorie. Confusing? Yes, but in reality it’s really simple: if you overeat you won’t lose weight, even while being in ketosis; more than that, if you overeat, you’ll put on fat, even if your carbs are 20g per day!
Should you stay low carb or keto? Well this is easier: the advantages of being in ketosis aren’t limited to weight loss, but extend to a better general health, especially a quicker and more effective reversal of type 2 diabetes; also, it seems that most people feel less hungry when having more fats rather than more carbs, and that’s certainly a factor to consider for a long term lifestyle.