What tissue is most important for determining the metabolic rate?

Answer 1

Muscle is a metabolic furnace that will burn additional calories 24 hours a day. Proper strength training will increase the amount of muscle you have. For example, if you add ten pounds of muscle in the next year, your body will consume/burn an additional 350 to 500 calories daily.

Answer 2

It's my understanding that collectively, your organs (particularly liver, heart, spleen, kidneys, and brain) are the most metabolically active tissues in your body, then muscle. Since we can't control the size of our organs, building up your muscles through strengthening exercises is the best way to raise one's resting metabolic rate. Regular aerobic exercise also temporarily raises your metabolism each time you do it, and overall burns calories.