Im new. :)

I am 21 years old and I've been recently diagnosed 1/3 obese, because ive never weighed more than, 140, but now i weight 200 pounds.. and I've asked my doctor, "how much do you think i should lose?" He said i should Atleast lose about 40-45 pounds and cut off dark sodas, chips, candies and eat healthier. Ive been working on it. I just need a little motivation to keep me active and lose weight.