Losing weight is tough. From adjusting your diet to ramping up your workouts, it often requires a serious lifestyle overhaul. Most men want to shed body fat while keeping or building muscle. But sometimes, in the quest to slim down, you might end up losing muscle instead of fat—and that can slow your progress and affect your strength.
“It’s bad to lose muscle instead of fat, because muscles are key players in body movement and function,” says Gerardo Miranda-Comas, M.D., Assistant Professor of Rehabilitation Medicine at Mount Sinai. “Loss of muscle mass negatively affects strength and endurance, leading to decreased performance in everyday activities.”
READ MORE: How to Create a Calorie Deficit and Actually Lose Weight
Here’s how to tell if your body is burning muscle instead of fat—and how to get back on track.
1. Your workouts feel harder than usual
If lifting weights or running feels unusually tough, it might be a sign your muscles are shrinking.
“You’ll notice less strength in the gym,” says Spencer Nadolsky, D.O., author of The Fat Loss Prescription. “The weight you used to manage for reps may feel heavier, or you may not complete as many reps as before.”
2. Everyday activities leave you exhausted
Muscle loss isn’t just visible in the gym. Struggling to carry groceries, climb stairs, or lift luggage can signal that your body is losing more than fat.
“Inadequate nutrition can decrease muscle mass, which leads to impaired function,” says Dr. Miranda-Comas. “Overtraining can also play a role if your activity level is very high.”
3. Your body fat percentage isn’t changing
If the scales are moving but your body fat remains the same, your muscle mass may be dropping.
“You’ll notice shrinking measurements, but the pinch-able fat stays the same,” explains Nadolsky.
4. You’re losing weight too quickly
Rapid weight loss might feel motivating, but it’s often muscle, not fat, that disappears first, unless you have a lot of fat to lose initially.
“Sustainable weight loss is a marathon, not a sprint,” says fitness coach Delbridge. “Aim for roughly 0.5–1 kg per week.”For tips from real guys who lost significant amounts of weight, check out our list of the year’s most jaw-dropping weight loss transformations.
5. Your workouts aren’t progressing
If you’re not increasing weights or reps, it could be a sign your muscles aren’t being properly nourished.
“Performance stagnation is a red flag that your body isn’t getting what it needs to maintain muscle,” says Albert Matheny, C.S.C.S., R.D., founder of Soho Strength Lab.
6. You’re constantly tired
Chronic fatigue may indicate that your body is running on empty. Without enough calories or carbs, your body can break down muscle for energy. “Lack of energy affects both daily life and workouts,” says Dr. Miranda-Comas.
READ MORE: Lost 50kg! Here’s How Our Reader Used Quick-Fire Workouts to Lose Weight Fast
How to protect your muscle while losing weight
- Eat enough protein: Lean meats, eggs, dairy, and plant-based sources help preserve muscle.
- Don’t cut calories too drastically: A moderate deficit of 200–500 calories per day works best for most men.
- Strength train consistently: Resistance exercises signal your body to keep muscle.
- Track your progress: Use measurements, strength gains, and body composition rather than relying only on the scale.
This article by Emily Shiffer, Melissa Matthews and Cori Ritchey, C.S.C.S. was originally published on Men’s Health US – additional reporting and products added by the Men’s Health SA team.
