The extra energy consumption from increased muscle mass makes a difference, but it's not even the most important reason. Skeletal muscle is a crucial part of the endocrine system in that it acts as a glucose sink. When blood glucose levels rise, if you have enough lean muscle mass then much of the glucose will be stored as glycogen in the muscles rather than being converted to fat and stored in that form. People who lose weight strictly through dieting without doing intensive strength training often end up "skinny fat" which is problematic for long-term metabolic health.

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