Last year while pregnant with my third child, I felt unusually tired. I reasoned that taking care of my two sons and growing a third was more than my body could handle. But then I noticed something else—my exhaustion peaked just after meal times. If I ate pizza, pasta, or a bagel, not only did I feel drowsy, but I felt like I had weights attached to my body. Every movement was sluggish, almost impossible. I couldn’t keep up with my daily routine, and my kids were spending time in front of the TV instead of with me. I went from...