Ms Pea makes an excellent point: if gammon is what it will take to stop you falling mouth first onto a pile of junk food, then have the gammon. It could be worse.
I think it would be foolish to imagine that it will have no effect. Cured meats are high in salt, which may cause water retention, and it is higher in fat and therefore calories. However, the effect may well be negligible.
The phrase 'it doesn't affect my losses' is always inaccurate, though... because you just don't know. Even under clinical trials it would be near impossible to determine what your weightloss would have been without it. the same input will have different effects on different people, or even on the same person from one week to the next.
If you're on the 'wide road', safely knowing you will get there but on your on terms and in your own time, then you can trade off the pleasure of the gammon against the potential that it might set you back. If time is of the essence, however - you stick exactly to the letter of the book... because that's guaranteed the fastest way.
