Weightloss Rules of Thumb: What are your favourites?

As with anything in life "it's a bit more complicated than that" can be applied to everything but we all use shortcuts that work nearly all the time for anything. So what is your favourite weight-related rule shortcut, why do you know it isn't perfect, and **why it is well worth using it regardless**? This post ain't intended to be contrarians only (maybe more for contrarians with perspective..). I've got two that I think about often; * 1% loss of bodyweight/week isn't officially recommended by any health bodies that I can find, but it is *so* good at both accounting for losing weight at higher bodyfat is typically easier and faster while also at lower bodyfats it's typically much [harder and slower](https://i.imgur.com/kQBXk6U.gif), the 1% recommendation succinctly explains that, even though no health bodies will adopt it as official advice. It's just such a perfect rule of thumb in that regards. * 3500calories = 1lb of weight loss. First off the obvious, it refers to just fat. Secondly, the actual number originally wasn't 3500, and these days it's estimated to vary between 3400 and 3800ish; it assumed a likely composition of fat but that varies not only individually, but in different parts of the body. Then we don't really account for the difference in lean mass loss. However, we **need** a rule of thumb to guide us and 3500 is perfectly acceptable as that; it's unlikely another number or a range would be more helpful: it's just one of the many reasons (and a minor one, at that) weight loss is non-linear. So for you, what rules of weightloss do you wrestle with being a 'bit more complicated' than at first glance, but still think it absolutely positively is a good rule none-the-less?