When clients come to us, they start out wanting it all. They want more muscle, less fat, better energy and maybe even a few visible abs. And they want it in the shortest possible time. And while resistance training has always been the go-to for body recomposition, there’s growing interest in combining it with time-restricted eating (TRE) such as the 16:8 protocol, where you fast for 16 hours and eat all your calories in just 8.
But does it actually work when you’re not dieting? What if you’re eating more to build muscle. Can TRE still give you that lean, muscular look without piling on fat?
A 2025 study by Blake and colleagues may finally give us the answer. And the results might surprise you.
What Is 16:8 Time-Restricted Eating (TRE)?
First, a quick refresher. Time-restricted eating isn’t about cutting calories, at least not on purpose. It simply means you eat all your food within a set window each day. The 16:8 version is one of the most popular, where you fast for 16 hours (including sleep) and eat during the remaining 8.
This usually means skipping breakfast and starting your first meal around midday, then wrapping up dinner by 8 p.m. It appeals to busy clients, those who aren’t hungry in the morning, or anyone who likes a bit of structure without full-blown meal plans.
It’s well-known for helping with fat loss, insulin sensitivity and appetite control. But can it build muscle as effectively as traditional eating patterns?
The Study That Put TRE to the Test During a Bulk
Researchers at California State University, including Menno Henselmans and Grant Tinsley, ran an 8-week experiment with well-trained men and women. Both groups lifted weights four times a week, ate a high-protein diet with a 10% calorie surplus and received whey protein after training. The only difference? One group followed a typical “eat throughout the day” pattern (the FED group), while the other ate everything within an 8-hour window, starting at least one hour after training (the TRE group).
So, what happened?
Both groups gained lean mass. That’s already a big win for TRE. In fact, the TRE group actually gained slightly more fat-free mass on average (+2.67 kg vs. +1.82 kg), though the difference wasn’t statistically massive. But what’s interesting is the FED group also gained 1.4 kg more fat. That’s a lot in just two months.
On the downside, the TRE group saw a bit less improvement in lower-body strength, particularly in squat 1RM, and reported lower energy levels midway through the study. They also performed fewer total reps across the training period. However, upper-body strength and muscular endurance were similar in both groups.
In summary:
| Outcome | TRE Group | FED Group |
|---|---|---|
| Fat-Free Mass (kg) | +2.67 | +1.82 |
| Fat Mass (kg) | +0.26 | +1.67 |
| Squat Strength Gain | Slightly lower | Higher |
| Subjective Energy | Lower | Higher |
| Overall Volume | Lower | Higher |
What Do Other Studies Say?
Blake et al. aren’t alone. A 2025 meta-analysis in the International Journal of Obesity looked at 15 randomised trials combining TRE with exercise. They concluded that TRE consistently reduced fat mass and body fat percentage while preserving muscle mass. Similarly, a 2024 review in Nutrients found that TRE with resistance training led to lower body weight, less fat and no reduction in muscle or strength.
Another interesting twist comes from a study on active women in 2025. It compared early TRE (e.g. eating from 8am–2pm) to delayed TRE (12pm–8pm). Both groups improved muscular endurance and maintained muscle thickness, but the earlier eaters lost more fat. So timing within the window might also matter.
Why Might TRE Work So Well for Recomposition?
There are a few theories. First, when you fast, your body naturally produces more growth hormone and reduces insulin. These are two changes that might support fat burning and lean mass retention. There’s also something to be said for reduced appetite and more structured eating. Even in a planned calorie surplus, the TRE group may have had fewer opportunities for snacking or underreported slight intake drops.
Another factor is energy availability. The TRE group trained in the morning but couldn’t eat for at least an hour afterward, which may have slightly hindered lower-body strength recovery, especially given the high training volume. Still, they built muscle and didn’t balloon in fat, which is a big win for many clients.
Also, when we fast, insulin levels drop and growth hormone rises, creating a hormonal environment that may favour fat use for fuel while preserving lean tissue. Once we eat (protein and carbs), insulin spikes, driving nutrients into muscle cells. This oscillation might create an efficient anabolic/anti-catabolic rhythm over time.
What This Means for Us
So what’s the takeaway here? If you’re designing hypertrophy programmes with a nutrition coach course mindset, TRE could be a useful tool for clients who want lean gains without feeling like they’re constantly stuffed or soft.
That said, it’s not for everyone. Athletes doing two-a-days, clients with demanding physical jobs, or those struggling with energy levels may need more evenly spaced meals. And if maximal strength is the main goal, like for someone on a strength & conditioning coach course, it might make sense to avoid long fasts that delay post-training nutrition.
But for a lot of everyday lifters trying to get bigger and leaner, TRE paired with solid resistance training might be the middle ground we’ve been looking for.
Final Thoughts
The idea that you must eat six times a day to build muscle is losing its grip. TRE shows promise not just for weight loss, but for smarter bulking. It helps clients gain more of what they want i.e. muscle, and less of what they don’t; fat.
As always, context matters. But if you’re looking to build lean mass in a sustainable, structured way and you’re open to a different approach, combining TRE with resistance training might be the smartest body recomposition strategy yet.
Reference:
- Blake, D. T., Hamane, C., Pacheco, C., Henselmans, M., Tinsley, G. M., Costa, P., Coburn, J. W., Campidell, T., & Galpin, A. J. (2025). Hypercaloric 16:8 time-restricted eating during 8 weeks of resistance exercise in well-trained men and women. Journal of the International Society of Sports Nutrition, 22(1), 2492184. Click here to review the full research article.
- Khalafi M, Maleki AH, Ehsanifar M, Symonds ME, Rosenkranz SK. Longer-term effects of intermittent fasting on body composition and cardiometabolic health in adults with overweight and obesity: A systematic review and meta-analysis. Obes Rev. 2025 Feb;26(2):e13855. Click here to review the full research article.
- Ho, Y.; Hou, X.; Sun, F.; Wong, S.H.S.; Zhang, X. Synergistic Effects of Time-Restricted Feeding and Resistance Training on Body Composition and Metabolic Health: A Systematic Review and Meta-Analysis. Nutrients 2024, Click here to review the full research article.
- Yu, Z.; Ueda, T. Early Time-Restricted Eating Improves Weight Loss While Preserving Muscle: An 8-Week Trial in Young Women. Nutrients 2025. Click here to review the full research article.
Build Muscle, Not Fat. Train Smarter with Nutrition & Exercise
Want to help clients build lean muscle without piling on fat? Our Nutrition & Exercise Specialist & Master Diplomas™ course give you the tools to design smarter training and nutrition plans. A 2025 study found that individuals following a high-protein diet with resistance training gained over 2.6kg of fat-free mass in just 8 weeks, while those combining it with time-restricted eating gained the same muscle but 1.4kg less fat. Another 2025 meta-analysis showed that pairing TRE with exercise significantly reduced body fat without sacrificing muscle. On this course, you’ll explore how to apply evidence-based strategies like these to real-world coaching, giving your clients the structure they need to train harder, recover better and see real results.
Nutrition & Exercise Specialist/Master – Distance Study, In-Person & Live-Virtual
Go From Personal Trainer to Nutrition Coach
If you’re already working as a personal trainer and want to support your clients beyond the gym floor, our Level 4 Nutrition Coach course is the next step. You’ll gain the knowledge and tools to give structured, evidence-based nutrition advice that fits seamlessly into your training programmes. Recent research shows that combining resistance training with a tailored eating window can reduce fat mass by over 1.5kg while preserving muscle, proving that nutrition timing and structure matter. Another 2025 review found that time-restricted eating helped exercisers lower body fat percentage without compromising performance. On this course, you’ll learn to interpret findings like these and turn them into real-world strategies your clients can stick to, while earning a CIMSPA-recognised Level 4 qualification.
Nutrition Coach Course – Distance Study
