A can of spinach and BAM — you are ready to take on the world. That is if you follow Popeye's theory, of course. Everyone has muscle and fat to a greater or lesser extent. Together with your bones and your organs, these things determine your weight. And regardless of what your weight was, you still gained a bit until 2018. Le Grand K (the kilogram) has become a few micrograms lighter over the centuries. A weight that determines your weight.