1) Lousy Attitude
Going too low-carb isn't just bad for your body, it's bad for your spirit. Extreme low-carb diets negatively impact your mood, says Jeannie Gazzainga-Moloo, Ph.D., R.D., a nutritionist in Sacramento, Calif.
Carbs supply your muscles with the glycogen you need to hit the gym. "Without them, you may feel weaker and more apathetic about training hard," says Lona Sandon, R.D., assistant professor of nutrition at UT Southwestern.