Taste is very closely related to smell, using many of the same nerves and areas of the brain. The taste buds on your tongue are more richly vascular in pregnancy, changing the taste of many things for you. Even food you've previously disliked may appeal to you.
Cravings are a natural part of pregnancy, with a complex set of factors that contribute to your hankering du jour. Sugar metabolism is altered, decreasing insulin's effectiveness. Fat is stored at a different rate; protein is metabolized differently. Thyroid hormone, closely related to the pregnancy hormone on a molecular level, affects appetite. The increased need for vitamins increases and a natural nurturing instinct can alter food choices. Salt metabolism changes affect thirst.
Today we're less rigorous about weight gain when not associated with diabetes. However, less rigorous attitudes about weight gain may be an important factor in the rise in the C-section rate. No matter how safe it's become, it's still an operation. And if avoiding surgery is important to you then you'll have to deal responsibly with your weight gain.
Each maternal-fetal unit is unique, and there is no formula to fit everyone. We know the diet must be adequate in calories, protein, essential fatty acids, minerals, and vitamins, but we also have to tolerate the occasional cravings that cumulatively may add only a few more pounds. Perhaps some humoral, endocrine, metabolic need is driving you to get something you need, even if it's chocolate.
If crave-binging becomes a substantial part of your diet, modern prenatal care will have to step in. But most women do extremely well, and satisfying an occasional craving will make life a little more tolerable for you during a time that can be physically and emotionally stressful.
Because of the tremendous changes in blood volume and your physiology's response to this cardiovascular change, you would think that being pregnant would bring about big changes in your ability to exercise. Actually, the maximum amount of exercise that you can tolerate goes down only a little. If you exercised regularly before pregnancy, you should be able to continue at only a slightly reduced rate.
As pregnancy continues, the larger uterus and heavier breasts may interfere by throwing off your center of gravity and making you feel like you're 99-percent belly. Still, exercise during pregnancy is beneficial for both you and your growing baby.
Before beginning or continuing any exercise program during pregnancy, be sure to get clearance from your doctor. Good rules of thumb are to drink plenty of water during exercise, stay off of your back, and avoid letting your heart rate go above 140 beats per minute. Sitting in a sauna or hot tub during pregnancy is inadvisable.