found this on the slimfast site
The number of recommended calories will depend on your current weight, height, and activity level. The lowest calorie amount we ever recommend is 1200 calories. It is not recommended to eat fewer than 1200 calories unless you are under direct physician supervision. Eating less than 1200 calories can lead you to be deficient in vitamins, minerals, and major nutrients such as protein. Moreover, eating too little can actually hinder weight loss. A good key for how many calories you should consume would be as follows:
Up to 140 lbs: 1300 calories
141-170 lbs: 1500 calories
171-200 lbs: 1700 calories
Over 200 lbs: 1900 calories
Sincerely,
Ali Auerbach, MS, RD
Registered Dietitian