[mondocat]

Despite the challenges in knowing calories in, much less calories out, agreed, just lowering your intake, and adjusting based on the outcome works, and is the only way to do sustainably do it. I was just challenging the assumption that calories out is fixed. In my case, I'm currently at a calorie deficit and losing weight (at 195, starting at 220), and at one point, I was at (or slightly below) 1000 calories a day for a month and did not lose a pound. (It was physically and emotionally miserable.) I went up to ~1500/day (and 2000 on gym days), and have lost 1.5 lbs/wk or so for months now. I don't think I "ruined" my metabolism, nad don't know if that was starvation mode or not, but I am convinced there's a calories "in" range in which your body will try its best to match calories "out", if only temporarily, and that I was in that range for a while.

[mondocat]

Of course I only know my weight and that it wasn't changing for a while despite an extreme calories deficit (from my previous norm, if not my expenditure at the time). I'm assuming that my calorie expenditure dropped, and not, for example, that I wasn't just retaining water sufficient to match the weight I would otherwise lose at the time.