Saying "fat people can lose weight" is an ableist comment. The issue isn't the size of a person- the issue is our society makes up a narrative that a certain population is less worthy. It used to be the other way around- fat individuals were held in high esteem. Royalty was always fat, as it was an outward way to portray riches. Those who were skinny were perceived as poor and/or underfed. Individuals may or may not be able to control their size, but we all can lose our judgmental perspectives.