It makes me sad when people like Benchmark don't want muscle, as they want to be as small as possible (though i am sure you don't need my patronising "sadness" Benchmark)
Yet, it saddens me that people do not want to be healthy (being fit, having a bit of muscle and fat) but would rather be skinny.
IMO, exercise is key. Daily exercise releases endorphins, it makes you feel good, it makes you feel less depressed and tired, it gives your metabolism a boost (even if you are resting, it sets the thermostat higher) and makes you look better (IMO, not stick thin but with bit of muscle, and maybe a bit of fat depending how you eat).
If you exercise every day, you can then eat three nice filling meals a day, include lots of veg, wholegrain carbs, lovely unprocessed natural tasty food.
Well, that works for me anyway, I eat well, I eat whenI am hungry, I eat quite a lot of quite nice food. Yet have maintained weight at BMI of 22.5 for over 10 yrs.
But like others have said, you have to find out what works for you. And what you want. I'd rather be strong than skinny, but I know I am an exception.