“In general, muscle is not lost before fat-it is very dependent on nutrition and activity volume,” Miranda-Comas says. “A person who is attempting to lose weight by not eating may lose weight in muscle first before fat.”
How does that happen? Well, the body likes to go for carbs (glucose) for energy first. If that’s not available, it goes for glycogen, which is glucose that’s been stored in the liver and muscles, says Dr. Miranda-Comas.
“Fat is also used for energy depending on duration of the physical activity, and an individual can train their body to use fat as the primary source of energy,” says Dr. Miranda-Comas. (Hello, ketosis-the basis of the keto diet.)