I have learnt to avoid lactose/dairy and any plants of the deadly nightshade family in undercooked/raw state (includes tomatoes, potatoes and aubergines). Hard cheese is OK, hadn't realised proper Brie should also be OK, in my working life I barely survived France on Emmental and Ham baguettes at motorway services. Most commercial outlets food is a time bomb!
And not a fan of sugar or meat that tastes like meat, though I may risk anything with loads of chillies (the proper really hot ones) and no tomatoes or cream or "meat", safe food is fish and chips (properly cooked, no firm middles or cheese coating on chips).
Long distance cycling is a good way of losing weight - sole input on most 200K rides is black coffee or water unless I can fit in a few beers. Emergency jelly babies (only Bassetts/Maynards) have got me home on longer rides though, I get pissed off with Weatherspoons fish and chips after a while.
Staying thin is easy when most commercially available food causes explosive weight loss, most of my calories come from rice and beer!
No plans to ever ride LEL or PBP purely on feeding/poisoning criteria.