#1. You’re losing fat and gaining muscle
Exercise changes your body composition. Simply put, fat takes up more space than muscle but doesn’t necessarily weigh less. That net positive change shows up in the way your clothes fit. (Oh hello, looser pants.)
While it can be a little discouraging to weigh the same thing you did when those pants felt tight, Barron says this indicates a change in your body composition. “This means that although your weight is staying the same, the percentage of fat tissue versus muscle tissue is changing — which is actually a much better indicator of health than weight alone.”
Body composition is what determines your total mass — it’s the sum total weight of the water, bone, muscle, organs, and fat that makes up your body. While your bone mass tends to stay pretty steady, the other factors can be fluid, changing both what you weigh and the size and shape of your body. Research has found that some unavoidable factors, like age, can alter your body composition over time, but others — like exercise — are under your control.
When you start exercising, especially if you’re weight training, you can lose fat and gain muscle. This may keep the scale steady (adding a pound of muscle and losing a pound of fat is a net zero equation) but it will help you lose inches. “Muscle tissue is denser than fat tissue, so it takes up less space,” says Barron. “This is exactly why your weight may not change, but your clothes are feeling looser.”
This is one of those situations where you should keep doing exactly what you’re doing. Don’t be tempted to stop weight training so that you don’t add muscle mass. This can backfire on you because when you lose lean muscle (which may happen when you lose weight), your metabolism can slow. “Your basal metabolic rate, or BMR, is generally the calories you're burning just existing — breathing and moving through your day doing the things you normally do,” says Audra Wilson, M.S., R.D., LDN, bariatric dietitian at the Northwestern Medicine Metabolic Health and Surgical Weight Loss Center in Geneva, Illinois. “However, when you lose mass, your BMR can go down a bit, too.”
