First of all, how fat is your girlfriend? Is it necessary to lose weight? Is her body mass index higher than the healthy level? Does she tend to have high blood sugar, high blood fat and high cholesterol at a young age? Is it because she doesn't exercise all day and eats junk food? Did she start to have psychological obstacles and shadows because she was fat?
If the answer is yes, then I fully support your idea and tell her directly, without euphemism, "Your weight is close to the dangerous value. Whether you like it or not, I will supervise your exercise and control your diet. It is absolutely impossible to become so fat. "
Generally, a girl who is so obese will be really nervous and anxious when she hears your words, but you are not rejecting her appearance at this time. Your starting point is to improve her life, so don't be afraid of the difficulties and contradictions at first. Persistence will definitely make her grateful.
She will definitely understand that losing weight and becoming a healthy and beautiful girl will make her feel happier than more cakes and fried chicken. Take her to a place with a high density of beautiful women, take her shopping to see clothes that look good but can't be worn, and clamor for losing weight. If it's not enough at a time, go shopping more times. If the answer is yes, don't be tactful, just tell her:
"Your weight is close to the dangerous value. Whether you like it or not, I will accompany you, supervise your exercise and control your diet. It is absolutely impossible to become so fat. "
It is not that I don't like her appearance. Your starting point is to improve her life, so don't be afraid of the difficulties and contradictions at first. Persistence will definitely make her grateful. She will surely understand that losing weight to become a healthy and beautiful girl is happier than any amount of cakes and fried chicken.
Health is all beautiful background, it is natural to be an ideal figure, but most chubby girls have a sensitive heart. If you want to persuade them, please understand, please accompany and be gentle.