I'm exactly the same for long, multi day walks. I start off fine, but then don't particularly have much of an appetite as I'm cranking out the miles. Waking up to a calorie-laden meal puts me off entirely, and I've started just having coffee + some sort of energy bar, with me having breakfast about 9am after I've walked for a bit and found a stream to wash up in. Dinners I've tried to keep as neutral as possible - I love strong tasting food when I'm at home, but cannot stomach a curry or something very spicy on a long hike, just makes me feel sick.