In my opinion, there may be two kinds of mentality when boys tell girls to lose weight:
(1) may be to let his girlfriend have a healthy body, but also a concern for his girlfriend:
If the girlfriend's obesity has affected her health, then the boy probably wants her to lose weight in the hope that she can control her weight and maintain a healthier state. A female friend of mine has many physical problems because she is too fat. Later, her boyfriend took her to the gym to lose weight, and her figure became much better after losing weight.
Therefore, when boys ask their girlfriends to lose weight, they should also look at whether their weight has really reached the point where they must lose weight.
(2) It may be vanity at work, and I hope my girlfriend is a slim girl;
A boy asks his girlfriend to lose weight, or he may want her to be a slim and beautiful girl, which will also make him more face-saving. Everyone loves beauty, so it is not ruled out that it is not because girls are fat that they are thin and ugly.
Although this mentality is understandable, if boys really care about the appearance of girls, they should also consider the real problems between you.
In any case, losing weight is related to your health. Girls should also consider their actual health status, and don't lose weight blindly because of a boyfriend's words.