This thread is a great example of Goodhart’s Law.
Here are some great examples. My favorite: In Hanoi, under French colonial rule, a program paying people a bounty for each rat tail handed in was intended to exterminate rats. Instead, it led to the farming of rats.
This is also related to the QS principle - only measure meaningful numbers. Your weight is not a meaningful number at all. For instance:
One of the best things you can do for your overall health and to lose fat is to build muscle through progressive resistance strength training. I think everyone who is dieting, counting calories, or watching their weight should throw all that crap out the window and start lifting barbells instead. But a gain of muscle may actually increase your weight (in a good way).
As others pointed out, weight fluctuations can be due to things like how much water is in your body, menstrual cycles, male hormonal cycles, seasonal metabolic patterns, how constipated you are, your circadian rhythm, and who knows what else. These fluctuations are basically meaningless so it makes no sense to track them.
And then, of course, there’s the weight you gain from eating a ton of junk food and storing it as fat, which is generally not a good thing for your health.
So weight gain can be good, neutral, or bad, depending on the situation.
When you measure the wrong thing, and try to optimize it, you end up doing bizarre things like trying to dehydrate yourself so your weight sticks to an arbitrary Yellow Brick Road, or a repeating cycle of binging and severe fasting, and there’s no way this actually gets you what you want. You’re tailoring your behavior to a meaningless number.
