As for losing weight, pregnancy is definitely not the time to diet or try to lose weight, but, being overweight in the first place, the Brewer diet may actually mean some weight loss as your baby grows. The Brewer diet is the right amount of food for an average sized woman growing a baby. It may be less than you normally eat, if you are an overeater. If you are a dieter, it may be more than you normally eat. The point is not to watch the scale, but to eat well.
Babies take a tremendous amount of calories to grow, and even more to nurse afterward.
But if you don't eat enough, they don't draw nutrients from your body. So your main goal is to eat right for your baby, and you may enjoy the benefits of the diet in other ways as well. A woman who gains that amount on junk food, however, will be gaining excess weight that her baby cannot use for nourishment, so it will be stored as fat rather than used for expanding the blood volume and growing her baby. After birth, that weight is not lost automatically because it's been stored as fat. That is why most women retain a few extra pounds after birth - so they can nurse their babies.