Because the muscles function as the engines of our bodies they play a major role in maintaining our metabolic rate. Even at rest, muscles account for almost 30% of the total calories burned because muscles require lots of caloric energy for muscle remodeling which happens 24 hours per day. For those who do not perform resistance training exercise, each pound of their muscle uses approximately 6 calories per day. However, for those of us who perform resistance exercise regularly each pound of our muscle uses approximately 9 calories per day because of higher levels of muscle remodeling and building stimulated by resistance training.
The key take home is that the resting energy requirements of strength trained muscles is 50% higher than the energy requirements of non-strength trained muscle! In addition stronger muscles allow you to perform physical activity at a higher level which increase the energy demands of exercise as well. Actual overall resting metabolic rate increases approximately 7% for 3 full days following a strength training session! Over the course of a year, this increase can add up to the energy contained in 10lbs of fat. Put another way strength trained muscles can help you lose 10lbs of fat over the course of a year.
Strength training is also highly effective for regulating blood sugar. Your muscles are you largest storage area for sugar, in the form of glycogen, so larger and stronger muscles help pull out more sugar from your blood. Strength training also increases insulin sensitivity and glycemic control for enhanced sugar transport from your blood to your muscles.
Resistance training has also been shown to reduce resting blood pressure and decrease LDL (bad) cholesterol. In fact the American Heart Association and the American Diabetes Association both recommend regular resistance training to combat cardiovascular disease and diabetes.