For years I have read that muscle weighs more than fat. I never believed it until now.

I can remember in high school watching friends issue each other a challenge to see who could lose weight the fastest. At the end of a week or two, whichever one had lost the least would say, "I've been exercising more, so I'm converting muscle to fat, and muscle weighs more." It sounded to me like an excuse for why the diet wasn't working. When by the end of a month both friends were back to looking and eating just as they had before, I was convinced I was right.

At Christmas last year we picked up our college son for the holidays. His roommate's mom said, "Don't the boys look great. No freshman 15 for our guys." The boys gave us an ear full. They had observed that dorm food didn't cause the notorious 15 pound weight gain for college freshmen. In their opinion it was binge drinking. "Too many carbs from pizza and beer," my son said bluntly, "that's the cause of the freshman 15."

That fall he had become interested in the weight room at the student rec center. In the spring he became serious about weight training. This summer he used some of his life guard money to join a gym.

He has gained 9 pounds - up to 164 from 155. He appears to be the same size. His clothes all still fit, and his waist is the same. He has noticeably added muscle, especially to his shoulders and chest. Even at that when I look at him, I think where is he hiding 9 pounds?

The only explanation is that muscle really is heavier than fat. It makes me want to join a gym. But don't let it be an excuse to fudge on the BTD!