Hi Reckless, Rochelle is correct, some diets carry higher vitamins and reduce the amount of calories you consume and some do the opposite.
When I was with eDiets they told me to have between 1,300 - 2500 cals per day but because I have a metabolic problem (hypothyroidism) 1300 made me gain a kilo per week until I reduced it to 800, then I was stabalized, hungry, getting ill and not losing.
The Tony Ferguson Program I discovered has us on around 680 calories per day (but if you exercise you have to eat more protein) They fill the meal sachets with heaps of vitamins and protein so your body can handle this amount of calories. Each body type is different and reacts differently to different diets. Luckily my hair is growing back, I don't feel hungry all the time and my sleep pattern has returned.
Here's a list of food with their caloric value - Link
Good luck in finding the diet program that works best for your body type.