We never recommend losing more than 1-2 pounds/week and therefore your calorie deficit should not exceed 1000calories/day unless there are unusual timeline circumstances. The calorie deficit number is the difference between your food intake and the calories you burn, and therefore the greater the deficit the faster you lose weight. But that’s the problem: everyone’s in a hurry. Large deficits are generally not sustainable, and can be unhealthy if you don’t supplement your diet properly. Not to mentioned that if you do reach your goal using a very low calorie diet, the journey will be miserable and you will probably end up rebounding for your own sanity.
That said, the more overweight you are the greater the deficit can be if time is an issue – but the slower you lose it, the greater your chance of long-term success. Additionally, you don't want to lose lean body mass (LBM/muscle) while losing weight. Unfortunately, during “traditional dieting" for weight loss, you lose both muscle and fat (1/4 muscle) unless you supplement and weight train. BUT even with weight training you can't lose any more than .7% of weight/week without losing muscle. For example, a person weighing 200 lbs can lose 1.4LB/wk (~750c/d deficit) - BUT they must supplement at least a daily multivitamin and mineral (MVM). The greater the deficit the more you need to supplement, meaning a MVM and pre/post workout formula is necessary to sustain LBM during dieting. Just make sure to fit your pre/post snacks into your allowed calories for the day. Maintaining or increasing LBM during weight loss helps you to burn more calories, feel better, avoid plateaus and reach your goal sooner. If you want to lose weight very quickly, but safely, use the dotFIT program. Create your goal and you will receive the ideal plan to get you there.