Hello.. Yes it commonly occurs when your thighs rub against each other... Not necessarily weight problem but also  occurs when you use tight inner wear and sweat a lot and wear the same cloth even after sweating... Try to wear cotton clothes... Breathable material... It's also common in humid weather conditions too... You can apply oil on that region and avoid inner wear in the night time...you can also use prickly heat powder in the crease area...thank you