The Science of Muscle Growth: What Comes After Fat Loss?
If you’ve spent the past few months getting leaner, building healthier habits, and improving your body composition—congrats! That’s a huge milestone. But what comes next?
For many people, the next step is shifting focus from fat loss to muscle growth. This phase, often referred to as “bulking” (though we prefer to call it lean muscle building), is where the real transformation begins—not just looking fit, but feeling strong, athletic, and powerful.
So, let’s break down the two key pillars of building muscle:
✅ A caloric surplus
✅ Progressive overload
1. Why You Need a Caloric Surplus
Muscle is expensive tissue. Your body won’t build it unless it knows you’ve got enough energy coming in to support recovery and growth. This means you need to be eating more calories than you burn—but not by much. Think of it like fuelling a construction site: too little, and the work can’t happen. Too much, and you’ve got materials spilling everywhere (aka unwanted fat gain).
💡 A good rule of thumb? Aim for a small surplus—around 5 - 15% above maintenance per day. Monitor your weight and adjust based on how your body responds.
2. What Is Progressive Overload?
Progressive overload is a fancy term for doing more over time.
That might mean:
Lifting heavier weights
Doing more reps
Increasing sets
Shortening rest periods
Improving form or range of motion
The idea is simple: if your training looks the same week after week, your body has no reason to adapt. To grow, you’ve got to challenge your muscles consistently—but smartly.
🙅♂️ It’s not about maxing out every session or chasing soreness.
✅ It’s about making small, intentional improvements over time.
3. When Should You Start Focusing on Muscle Growth?
We usually recommend switching to a muscle-building phase once you’ve reached a body composition you’re happy with and feel confident maintaining it.
This transition is perfect for clients who:
Have established strong training habits
Have a good understanding of nutrition
Are no longer trying to drop body fat
Want to feel stronger, more athletic, and perform better
4. What to Expect
Expect the scale to go up—and that’s a good thing.
Done right, most of that weight will be lean mass. Clothes might feel different (in a good way). You’ll likely have more energy, better performance in the gym, and notice increased muscle definition over time.
This is also a great time to dial in:
Sleep quality
Recovery days
Protein intake (aim for 1.6–2.2g per kg of bodyweight)
Consistency in your training program
Final Thoughts
If fat loss was your first chapter, muscle growth comes next—and it’s one where you get to eat more and lift heavier.
To be clear - this does not mean you can’t do both at the same time (drop body fat and build muscle). BUT - you can’t optimise both at the same time. If that doesn’t make complete sense to you, click here to read our previous blog: “can you build muscle and drop body fat at the same time”
Need help structuring your muscle-building phase? Book a free intro to see if/how we can help.
