A prolonged period of inactivity- whether it is caused by an injury or by life factors like work, school, or personal demands- typically results in a loss of muscle mass. One critical factor in determining your metabolic thermostat’s set point is the amount of healthy muscle that you have. Building muscle is difficult and losing it is easy. Seven days of a sedentary lifestyle can result in decreased strength and loss of muscle. This is a very common cause of weight gain in my practice. I’ve heard many, many stories of patients who were a few pounds overweight, but remained active until they injured their back or knee, or suffered some other injury that prevented them from remaining active. These events often result in 40-50 pounds of weight gain that is often irreversible.
Another way that injury can cause weight gain is by blocking the functionality of the overfed side of your metabolic thermostat. When you gain those first few pounds, a functional metabolic thermostat will result in an increase in your metabolism and you will (subconsciously) be more willing to walk faster, take the stairs, go to the gym, or perform any other activities that will burn more calories. However, if every time you stand up to move, you experience pain from your injury, your body will be inhibited from burning off these calories. As mentioned above, any factors that impede the proper functioning of the overfed side of your metabolic thermostat will result in an often permanent increase in your set point.