Losing weight

What the best way to get to 51kg?
I think i'm getting really fat now. i just want to be 51kg then my life would be better. any advice on how to get to 51kg.
Should i eat nothing except lettuce for a week? would that work?
Does lettuce have negative calories?
I really want to be 51/50kg because I feel better at that weight but i gained weight and i find it hard to get back there.
Any advice?
i don't want to gain muscle. last time i gained muscle i had eat nothing for 3 days and cut out protein from my diet for 3 weeks.

[Renee Radenberg]

If your measurements are correct, your present weight is underweight for your height. 61kg is the proper weight for your height. A healthy way to eat is a Heart Healthy diet which means a moderate fat diet to benefit your body. Moderate fat diet means = use polyunsaturated (omega 3, corn oil, nuts, etc) fats and monounsaturated (olive oil, canola oil, peanut oil, etc) fats, no saturated fats (high fat snack foods, butter, fat spreads) and no trans fats. Eat low fat meats (chicken, fish, loin of pork) or non-meat sources (soy products, nuts), low fat vegetarian combinations (rice & beans, pasta & beans, low fat cheese & pasta), low fat and substitute dairy products (1% milk, low fat/fat free yogurts, low fat soy milk/soy yogurt), use plant oils, non trans-fat margarines, and eat a lot of fruits and vegetables. Eat daily high fiber breads and cereals (oatmeal).