LiveFromNY, 170cm is about 5'8'' and 100kg is about 220lbs.
large_smile, start with your diet. What's your current diet? Try to cut out soda, candy, pastries (cakes, donuts, cookies, etc.), and fried foods. Natural is good, and get lots of fruits and veggies in your diet. Replace white bread with whole grain bread (same with pasta and rice - brown rice). Drink nonfat milk. Get lean protein, fish, and beans.