There's this guy, apparently a former football player who then gained some weight, lost about 50lbs on lowcarb (which for a guy, probably took all of 3 months if that, if LC was done right). Now he eats LC most the time and 'whatever he wants' one day a week.
That's actually more moderate than most in his category. Most go back to high carb eating, and shift to LC once in awhile if they have gained more than 10 pounds. People like this, they don't have any metabolic issue really. They got fat because they ate too much and often ceased previous activity (not unusual for people who are athletes in high school or college).
For them, lowcarb is hobby. Or as he put it, just a 'tool'. There is no reason for them to make it an entire lifestyle. Why should they? They don't need to.
Most the people on lowcarb that I know don't do it for fun or a handy discipline. They do it because if they don't do it, they will go diabetic or continue gaining weight, either of which lead to the "...or they will die" option.
Those are the people who tend to have massive carb cravings if they mess up their diet. They are the people who tend to have a much more difficult time staying on-plan as a result. They are the people who have to moderate their carbs because the side effects of not doing so are just too problematic.
They can usually have 'treats' -- things higher than their normal carbs -- sometimes without a big deal. But actual 'cheats' -- a whole carbfest meal -- will hurt.
One of the things most people don't get about lowcarb is that the "one bite won't hurt you" theory is wrong. On a calorie diet, it works that way. So you go over calories. That's just a few less saved that day. Eat less the next day. Big deal. Don't do it regularly if you want to lose weight.
If you go too far over carbs, it's an entirely different story. The result is one of four things:
1. potentially nothing, usually if it's not a big excess, and/or you've been doing this a long time so your body's adapted, or you're really seriously in ketosis so it'd take more than that to push you out. Do it regularly though and it'll be one of the other options.
2. nothing happens to your ketogenic state but you start craving carbs within a couple of days, cravings so strong they are near the level of drug-addiction-withdrawals in intensity. The risk of going offplan jumps into the stratosphere during those times.
3. you literally knock yourself out of keto and you have to completely re-do induction... 1-3 weeks of ultra lowcarb, harder than the average period for most.
4. you stall, meaning you were losing weight consistently and suddenly that just stops happening and may take days or a week to see again. This one can happen in conjunction with any of the three above.
When a person treats carbs like calories, you can be sure they are lowcarbing for convenience, not "to save their life." If it were different, you wouldn't need to debate with them; they would aleady know, probably the hard way.
I got all snarky because when someone like that pops up on a thread where someone is saying, "Gosh, I so want to cheat and eat this 120 carbs treat!" (equivalent to 12 pieces of regular bread toast, or 4 candy bars), and someone who does LC as a hobby essentially tells them hey why the hell not, go for it, it's not gonna hurt anything... well you know, that's a bummer, 'cause it really might and if they weren't looking for an excuse they wouldn't have asked other people to justify it for them.
If you tell someone you're going to the annual fair and gosh those funnel cakes call you, they'll tell you that you gotta be strong. Yet often the same people will say it's ok to blow it on thanksgiving or christmas. What's the difference? They both only come once a year! It's an example of the fact that most of lowcarb philosophy is a subjective mental state.
Atkins used to say, "One bite WILL hurt you." You have to truly get OFF the sugars and stay off them. But for LC hobbyists, even one DAY doesn't hurt them, maybe more. So they're all for encouraging people to not only go ahead and 'cheat' -- but hell, even PLAN cheating, because who can possibly just adapt a different eating plan forever, they say? Who could have the discipline to eat foods that are good for you -- or at least, if they aren't, are deliberately created to be fairly low carb -- on an ongoing basis?
Hmmmn. Maybe people who be insanely fat or DIE if they don't? Could be.
It's tough because when some hobbyist lost some weight with LC they figure they're now the expert on all things lowcarb I guess, because they are a success story. Which is great, more power to them. But that only makes them an expert on how to eat low carb for a few months to lose it, and how to eat it "as often as may be convenient for them" after that. It doesn't necessarily make them an expert on the 1001 more detailed body chemistry issues that are behind why most people eat lowcarb.
The difference in effect on the body, on seriousness about the eating plan, on attitude toward high-carb food, and -- most importantly -- in consequence of violating the eating plan -- is huge.
I guess I wish more people realized that.