Goal: loose 30 lbs in 6 months

You can do it but you're going to have to be serious about it and not give up. If you really want that dress you gonna have to work for it

This is achievable - even with diet alone. Though exercise will help - I would aim for a stretch goal of 4.5 months (Put a plan in to shed a little higher than your target so your fitting will be in well ahead of time. If it was me I would track your weight (weigh same time every day and look for a trend line don't worry if you are up one day and down the next this is normal we are looking for an average loss but I find that daily measurements give prompter feedback than weekly) - log all your foods on here and aim for a deficit (Be wary of how much of your exercise cals you eat back but some exercise will help you be able to eat a little more and "buffer" weight loss).

Make sure you account for the food you eat and log calories here to keep you on track (accurately - get a set of scales). For my guideline of 4.5 months you need a deficit of around (based on 7,700 cal per 1KG body fat and assuming you lose fat and not muscle - this is where some exercise will help you keep lean muscle) - anyhow the deficit required per day would be around: 700 cal per day on average to achieve this weight loss in 4.5 months. Assuming you have a base metabolic rate of 1,800 per day this puts you around the 1,100 cal per day now this is too low for a healthy diet so if you exercise (even around 2miles walking each day = 200 calories which will put you in at around 1,200 - 1,300 Cals of food a day and you should be there in 4.5 months). Use for motivation - things like that 200 cal biscuit is equivalent energy to walk 2.0 miles do you really want that second biscuit now? It is not about good or bad food it is about everything in the correct moderation - plan your treats do not deny yourself that scoop of ice cream of chococlate etc... just plan it in.