Opiates make you crave sugary foods and junk food. Unfortunately since heroin is Luna’s entire personality, who knows the last time she ate a fruit or vegetableI suppose heroin will do that.
I don't think she'd look as bad if she actually ate anything except junk food. Has she ever posted a pic of an actual decent balanced meal with any protein? The closest I saw was when her EVIL HORRIBLE dad took her for hamburger sliders and fries, which is still junk food but at least cooked and doesn't have a shelf life of 1+ years. Apart from that she survives solely on packaged junk food. She's eaten fruit a few times tbf but garbage can fruit doth not a healthy life make. If I didn't care that it went straight in her arm I'd pay her to use a body fat analysis machine. The results would be fascinating.
If she took all the money she spends on junk food and all the time she spends in bed e-begging she'd be able to cook cheap healthy meals and look significantly better.