If i do a spin class 5 times a week and eliminate all junk food and eat no more then 1200 calories a day, ?

If your intake isn't enough, you may hinder your results. Eat as many non-starchy vegetables as you wish, limit potatoes, sugar, bread, etc. Fruits are great, lots of water, lots of protein - lean - chicken or fish. Watch that your body doesn't kick into "starvation mode" or it'll hold onto whatever you put in. Also - find a good multivitamin. Speak to your trainer or nutritionist for helpful advice. And don't forget muscle is heavier than fat. Stop watching the scale and focus on tightening your body. In fact, you really should add some weights to your routine. Faster and more dramatic results...