Most fuck it up by misunderstanding CICO and eating ranch-covered salads and 3000 calories of bread and rice and cereal and shit like that.  They think in terms of halo effects ("I ate a salad!"/"they're fat-free!") and not calorie counts.  Which deliberately makes weight loss much harder than it has to be (likewise with the fake low calorie counts on MFP, you'll gain weight from excess calories regardless of how much you cook the books so it's better to get an accurate picture). For example, my mother gets unsalted-tops saltines, low-sodium chips (with ranch dip, on the logic that it's tastier than buying non-bland ranch-flavored chips that have the exact same calories as plain ones), and low-sodium V8 because "it's healthier."  I don't know if her doctor told her to do this, but I doubt it, because she's certainly not old enough for blood pressure to be an issue and she's never mentioned blood pressure or excess sodium when discussing her health problems.  She'd rather eat bland low-sodium beetus crap than eat fewer calories.