When you start to get into around the 10th week and beyond, there's a wall you can hit if you aren't eating well enough. This is not really an issue on American or European long-distance trails where any sort of nutrition one desires can be arranged in your resupplies (and you can eat ravenously on town days) but if you do multi-month trips in the 3rd world, you'll find trail legs don't last forever when all you're eating is rice and some kind of legume for every meal. At a certain point the lack of high-quality nutrition starts to make you progressively weaker.
That was 5 years ago and I managed to mantain that weight by taking care of what I eat. I think that trip changed something in my metabolism and helped to know myself better.