"Should I be fasting?"

Fasting has become close to a default recommendation in health circles. For some people it works well. For others, especially men who are training hard, eating too little or fasting too long can backfire on their hormones. One example is SHBG, a protein that binds testosterone in the blood. Long stretches of fasting and not eating enough tend to push SHBG up. When that happens, total testosterone can look fine on paper while free testosterone, the part the body can actually use, drops. That can show up as weight gain, trouble building muscle, poor sleep, fatigue and mental sluggishness. I've seen people try to improve their health with more fasting and end up feeling worse without knowing why. That's why I like to look at total and free testosterone, SHBG and DHEA together, and then talk about how someone is eating, training and sleeping. DHEA is a precursor the body uses to make other hormones, and it tends to decline with age, so it adds context to the picture. If fasting is part of someone's routine, the right amount depends on the person. I don't think a blanket recommendation that everyone should fast makes sense.