Because going on a low - calorie diet increases cortisol levels in your body. (dietselfhelp.com)
Research shows that workouts which are longer than an hour spike cortisol levels in your body and additionally decrease testosterone. (toptestosteroneboosters.org)
Cortisol testing has demonstrated that interaction with dogs often lowers cortisol levels in our bodies, demonstrating that our stress levels are going down (wileypup.com)