This is also my experience, although I don't actually measure ketones. At 190 pounds a low carb diet, with no attempt to control protein and eating a bit too much peanut butter or cheese still gave me weight loss. The less I weigh, the less insulinogenic my diet seems to need to be for me to maintain, even small overindulgences in carbohydrate leave me with an increased appetite for a couple days, large overindulgences throw me off for a week.

It makes sense to be more rather than less sensitive to the fattening effects of insulin once you've lost weight, at the heavier body weight we're likely to be more insulin resistant. The lower the body weight you're trying to maintain, the lower insulin might need to be.