I'm looking to build a character that stands out from his hometown, where everyone else is somewhere on the Obese Defect chain (Jester Dragon's Guide to Defects) while he fares well with barely anything. I'll go for anything that either reduces the amount of food he needs or increases how long he can go without food, preferably something I can get through a feat.
Aside from the Ring of Sustenance? The 3rd level power of the Verdant Bloodline (Sorcerer) grants a similar effect. You can get access to it through feats.
Alternatively, if you have access to Blood of Angels, and a permissive GM, you could get the "Gain Sustenance from Sunlight" ability with an Aasimar character.
The faith trait Self-Sustaining can get you purify food and drink as a 1/day SLA. Then you could buy/scavenge rotten food, then purify and eat it in private. You'll still be eating just as much but your neighbors won't realize it.
Closer to what you requested but requiring more investment, an Unchained monk can get this ability:
A monk with this ability uses his ki to control his metabolism. As long as he has at least 1 point remaining in his ki pool, the monk needs to eat and drink only 1/4 as often as normal, needs only 2 hours of sleep each night (including to replenish his ki pool), and can hold his breath for up to 1 hour per point of Constitution. As a move action, he can spend 1 ki point to enter a state of suspended animation, falling unconscious and appearing dead to all senses. At the time he enters this state, he indicates a preset period of time or a triggering condition, after which he awakens.