I'm not wedded to the idea of CICO by a long stretch. But I do need to lose weight, and have found that by hugely upping my walking at the weekends, if I ignore calories in the following days and eat an amount of food that 'feels right', I gain weight and my blood sugar goes up. I've been struggling with this for months. Spot checks have confirmed that I have indeed been eating well over an estimate of maintenance calories.
I see counting carbs as the same as counting calories - I've proven that it's silly for me not to do either. Everyone is going to have a different metabolism and so a generic equation for CICO is of no use, and everyone has a different reaction to carbs to a blanket figure for carbs is of no use. But both are of great use when applied to ourselves as individuals. And just as our carb tolerance may increase / worsen, we also need to be aware that as we lose weight, our resting metabolism are almost sure to lower.
So I'd like to get a rough feel for things, to make sure I'm always in a deficit. I've discovered that whenever I stop being in a deficit and things take a while to get back on track. I presume it's as simple as that my liver starts filling up with fat again. Everything seems to go much better when I'm constantly losing weight, but there will be days when I get very hungry as a result of the exercise so I need to start logging things and getting a feel.
Re CICO, I've been reading/watching Fung quit a bit recently. Even he says it's not a bad basis, but what people almost deliberately overlook is that we know full well, that once a person has been overweight, if they then lose weight, Calories Out reduces, and often quite remarkably.
So I'm expecting that if and when I reach a weight I'm comfortable with, I'll be needing to eat far less than someone of the same age, size and gender as I am who has never been overweight. If I can eat 1600 calories a day and not gain weight I'll be pleased, even though the same-sized man next to me will be able to eat 2,200 for example.
I did consider fasting in order to lose weight, but I can't do it as often as I want so I'm going to just get on with it in the normal way.
Also, while I did briefly get very excited by the short-term studies involving things like alternate day fasting, which show that's a much better strategy for losing weight while preserving metabolism, it seems the long-term results are not so great in actual practice:
https://onlinelibrary.wiley.com/doi/pdf/10.1002/osp4.52
It's a bit like LCHF - short term studies say it's better for losing weight than HCLF, but after a year it all evens out.
Even studies on the speed of weight loss show that rapid vs slow has pros and cons. Slow results in a lot of metabolic slowdown, and fast results in a little bit more. But fast results in better improvements in insulin levels and glucose control.
It's swings and roundabouts. To be honest, I just need to lose weight, and what with upping the exercise, I want to get a feel for things, so even on days when I get very hungry, I can eat enough but not too much.
Here's the way I think of things after some recent reading around:
* Weight loss, rapid or otherwise, is not the problem that causes a slowed metabolism. Being obese is the problem. Once you've been obese, any method of losing weight is going to slow your metabolism in the long run. No study has found a way to lose weight without slowing your metabolism in the long run.
* A slowed metabolism is not a wrecked metabolism. It's still ticking along fine. You could even argue it's an improved, more efficient metabolism.
* Constant moderate calorie restriction is not evil. It actually makes almost all bio markers for health and life expectancy increase every time it has been tested on any species.
* One thing nobody argues with is that it seems there is a time limit before weight loss stops working to help improve pancreatic function in people with T2. I'd rather not carry on letting what's happen to my weight happen again. I lost a lot of weight last year, then stopped counting calories, and sure enough verified I was over-eating, and now my weight has increased and my blood sugar has been dangerous for a while. Even on very low carbs.
* The vast majority of the time I've read T2 people on this forum talking about their experiences with improving their blood sugars, they talk of weight loss, and weight loss stalls. Doesn't matter whether they are LCHF, keto, fasting, whatever. So their metabolism has slowed. That's just what happens, and once we've been overweight, we need to expect this to happen if we want to lose weight.
Sorry this sounds like a rant when I've just re-read it before posting, it's just a mind-spew of my current thinking. I was actually going to start a thread on this but it seemed appropriate in this context.