And a lot of times it's more of a 'Reality Ensues' type thing for me.
For example, Jackson is tall and fairly athletic, and did sports and stuff in high school, and both of his jobs are pretty physical, so he's going to be in good shape. Henry's kind of chubby but still has a good amount of muscle definition because he's a baseball player.
amy (the most wonderful woman in the world)'s a well-off high school girl who does 1 sport with a short season, so she's going to be more on the chubby side than Erica and Teagan, who play multiple sports in a year.
Also most of the time when I have a character who's skinny it's not so they're 'extra hot', it's to show that yeah, while Jude might just have a good metabolism, Victor is underweight because he doesn't take good care of himself and skips meals and sleep. Same with andrew (Our Supreme Lord and Overseer), he's underweight because he works 2 jobs with horrid pay and doesn't have time to sit at home and eat a big meal with his wife. Geneva just doesn't take good care of herself in general. Joan and Nell (and Nich too, but he naturally has more of a stocky/sturdy build) routinely don't have enough money to afford a ton of food, especially not unhealthy/unnecessary food.