Muscle growth potential is primarily determined by genetic factors, varying between individuals. From January 2024 to March 2025, natural bodybuilder Jeff Nippard set out to challenge the limits of natural muscle growth with a meticulous, year-long experiment.
Had the science-based hypertrophy expert maxed out his drug-free gains after 15 years of lifting? Over his 14-month physique transformation, Nippard bulked for six months, followed by recomposition and cutting phases. He never skipped a workout, trained intentionally, and tracked calories daily. Nippard’s untrained biological brother, Brad, also participated in the challenge.
Baseline Testing and Hypothesis
For accuracy, Nippard measured his body composition using DEXA scan and ultrasound for muscle thickness—the gold-standard tests. He set an ambitious goal: Gain four pounds of muscle. Brad Nippard aimed for approximately nine pounds.
I think if I give it my all for a year, I’ll see some new growth.
—Jeff Nippard
The before-and-after photos were taken using the same variables (e.g., lighting, clothing, angles, etc.).
[Related: The 7 Ways Genetics Impact Bodybuilders, From Pro Coach Joe Bennett]
Training Protocol and Methodology
The Nippard brothers followed the same workout program, consisting of two strength sessions (upper-lower) and three weekly push-pull-legs (hypertrophy workouts) with two rest days. The protocol included three key strategies:
- Training to failure on the last set of every exercise.
- Focusing only on proven exercises.
- Strict progressive overloading.
Even on heavy compound lifts like presses and squats, I’m pushing that last set until I cannot get the weight up.
—Jeff Nippard
While it’s unclear how crucial failure training is for hypertrophy, research has shown increased progress the closer sets are to failure. (1)
Nutrition and Supplements
The Nippard brothers bulked on 3,000 calories daily: 150 grams (g) of protein, 410g of carbs, and 85g of fat. That’s 15% above Jeff’s maintenance calories, aiming for a two-pound monthly weight gain. While Brad, starting at 33% body fat, would usually be prescribed a lower-calorie, fat-loss diet, all variables had to be equal for the experiment.
The Nippard brothers prioritized consistent sleep schedules, tracking shuteye quality via Aura Rings, as sleep regularity impacts body composition. (2) These are the supplements used:
Progress and Checkpoints
The Nippard brothers retested body composition and weight one month after starting the program. The results were:
1-Month Check-In
Brad gained 12.7 pounds of lean mass (muscle and water) and lost nearly 3% body fat. Surprisingly, Jeff gained three pounds of lean mass, with a little fat gain.
Jeff posited that Brad’s initial gains were water weight due to creatine and high-volume training.
6-Month Bulk Results
Both Nippards gained 15 pounds. Brad retained 13 lean pounds while losing 1.2% body fat. Jeff added 4.5 pounds of lean mass but gained 11 pounds of fat.
This shows the power of building muscle. My body fat went from 15% to just over 20%. That’s a bit much.
—Jeff Nippard
Recomp and Cut Phases
Could Jeff continue gaining muscle while losing body fat? To test it, he consumed 2,800 calories daily (160g protein, 335g carbs, and 85g fat) for three months. While his strength gains plateaued a few weeks in, Jeff felt and looked better than he expected thanks to his newfound gains. After the recomp phase, Jeff lost 0.8 lbs of lean mass, within DEXA’s error margin, and 0.5 lbs of fat.
It’s disappointing but expected. At my level of advancement, you need a caloric surplus to keep gaining muscle. Maintenance calories probably won’t cut it.
—Jeff Nippard
Briefly switching to a full-body split could have thrown off Jeff’s progress. A knee injury during a max effort test slightly hindered his performance.
Final Results
After a fat loss phase, 14 months later, the Nippards retested at the same body weights:
- Brad gained 10 pounds of lean mass and lost 10 pounds of fat.
- Jeff retained 2.7 pounds of lean mass, dropping from 15.8% to 14.5% body fat.
You can push your natural ceiling up with optimized training and diet.
—Jeff Nippard
Despite being an advanced lifter, Nippard proved that gains are achievable with strategy and consistency. While he believes a natural ceiling exists, it seems still undetermined how high it is.
More In Research
- Build Muscle, Lose Fat — Intermittent Fasting, Resistance Training, or Both?
- Train Past Failure for the Thickest Calves
- Is the Overhead Press Worth It for Hypertrophy?
References
- Robinson ZP, Pelland JC, Remmert JF, Refalo MC, Jukic I, Steele J, Zourdos MC. Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions. Sports Med. 2024 Sep;54(9):2209-2231. doi: 10.1007/s40279-024-02069-2. Epub 2024 Jul 6. PMID: 38970765.
- Baron KG, Reid KJ, Kern AS, Zee PC. Role of sleep timing in caloric intake and BMI. Obesity (Silver Spring). 2011 Jul;19(7):1374-81. doi: 10.1038/oby.2011.100. Epub 2011 Apr 28. PMID: 21527892.
Featured image: @jeffnippard on Instagram
