Though seriously women didn't use to eat so much when they got pregnant. Personally I think that was probably healthier, as opposed to added 50 lbs during the pregnancy and then trying to lose it after.
Some women seem to always be fighting the urge to eat and gain weight. When they get pregnant they have an excuse to not watch what they eat. (They're eating for the baby's sake.) So they end up putting on more weight than is necessary.
Actually, doctors consider gaining weight during pregnancy to be healthy-- 25-37 pounds for a woman who is of normal weight. It's even recommended that overweight women gain weight.
From this website:
"Weight gain during pregnancy helps your baby grow. Gaining weight at a steady rate within recommended boundaries can also lower your chance of having hemorrhoids, varicose veins, stretch marks, backache, fatigue, indigestion, and shortness of breath during pregnancy.
The extra weight you gain during pregnancy provides nourishment to your developing baby and is also stored for breastfeeding your baby after delivery."
In some ways, you're right-- women should concentrate on being healthy over eating large amount of the foods they restricted before they got pregnant. But it's altogether necessary that a woman gain weight for her health and for the health of the baby. There's a trend among some women to not gain during pregnancy, and doctors will tell you that it's unhealthy. Pregnant and breastfeeding moms are generally told not to restrict their food intake while pregnant or breastfeeding.
In my case, I gained the weight I was supposed to, but some of that was due to being sick and in bed during most of my pregnancy. I simply had a harder time taking it off because I wasn't able to breastfeed.
I know what you've both said is conventional wisdom in our weight-obsessed society, but until you voice your opinion, be sure to do your research. You also have to consider how much pregnancy affects all parts of a woman's body-- including her energy levels, metabolism, level of hunger, and general mental state. Sometimes, when you're pregnant, the last thing you're able to do is stick to any workout regimen (even reduced) and watch what you eat. Pregnancy is hard on the body and the mind.
Here's an article on why doctors now consider this weight gain to be healthier than they did 30 years ago:
Howstuffworks "Weight Gain During Pregnancy"