The recommended amount of weight depends on the weight prior to pregnancy. If you started a healthy weight, the Institute of Medicine recommends 25 to 35 pounds over the course of the pregnancy. If overweight, 15 to 25 pounds, and if underweight, 28 to 40 pounds.
There are risks associated with either gaining too much weight or gaining too little. Too much weight can cause the babies to be large, which can lead to complications during labor. Starting pregnancy overweight also increases the risk of gestational diabetes and preeclampsia. It is also associated with childhood obesity. Starting pregnancy underweight or gaining too little weight during the pregnancy increases the risk of preterm delivery and low-weight babies.
So what can you do to gain the right amount of weight? I don't recommend eating for 2, but you can add a snack or a small meal that's about 300 calories. So one of the snacks I like to recommend for women is a peanut-butter sandwich cut into quarters; that way you can continue to eat it throughout the day whenever you need just a small snack. It's important to eat healthy, maintain exercise, and drink water. And talk to your provider at each visit to make sure you're gaining the appropriate amount of weight. If you need any additional guidance, you can always talk to a dietitian as well.