https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP279449
Surrounding the stomach are nerves that detect when the stomach is stretching and relay this signal to the brain which makes us feel full. This study found that in people who are obese the nerves around their stomach are less sensitive to stretching. This will mean that obese people will not feel as full after a meal that would otherwise bring on the feeling of fullness.