Fitness icon Arnold Schwarzenegger answered fan questions about diet and exercise with tips on getting more protein and building muscle in the gym.

Another protein in the body that becomes highly active during exercise is NR4A. Benjamin Sung, Thomson's research assistant, is leading a project to figure out why this happens.

As we age, we tend to gain belly fat and lose muscle mass, but eating a lower-calorie Mediterranean diet combined with light exercise could prevent this, a new study found.