Start with a modest surplus: reviews suggest about 10–20% above maintenance#
If your goal is to build muscle, a sensible start is a modest surplus, smaller than bulking culture suggests; the ideal amount is uncertain. A review of nutrition for natural bodybuilders recommends a surplus of about 10–20% above maintenance, aiming for 0.25–0.5% of body weight gained per week for novice and intermediate lifters, and less for advanced ones1. A second review, reasoning from a different starting point, suggests a conservative 1,500–2,000 kJ a day, or roughly 360–480 kcal by our conversion; the two figures are framed differently and aren't strictly equivalent2.
The reason for a small surplus is simple. Muscle grows slowly, at a pace set mainly by training and training age. Food eaten well beyond what that growth can use is likely to be stored largely as fat. Both reviews are also clear that nobody has pinned down a single "optimal" surplus. There isn't one number that fits everyone, and anyone quoting one is going beyond the evidence.
Most of this blog is about deficits; our guide to calorie deficits covers that side. This piece runs the same arithmetic in reverse.
What the two reviews recommend, and what the ranges mean in practice#
The two reviews reach broadly overlapping advice by different reasoning.
Iraki and colleagues (2019) reviewed off-season bodybuilding nutrition, the phase when lifters try to add muscle without adding "unnecessary body fat." They recommend a 10–20% surplus, weekly gain of 0.25–0.5% of body weight for novice and intermediate lifters, a more conservative surplus for advanced lifters, and protein of 1.6–2.2 g per kg per day1. It is a narrative review, meaning expert synthesis rather than a pooled statistical analysis.
Slater and colleagues (2019) asked whether a surplus is needed at all, and how big it should be. They note that textbook figures range from about 1,500–2,000 kJ a day up to 4,000 kJ for people who struggle to gain. They also note that these figures rest on assumed energy content of new tissue and ignore the body's own adjustments: in one overfeeding study they cite, spontaneous daily movement rose by about 1,380 kJ a day when people were overfed 4,200 kJ a day. Their conclusion is that practitioners should take "a conservative approach" of about 1,500–2,000 kJ a day, with regular checks on body composition and strength, because the ideal surplus "has never been validated" in people who lift2.
Here is what those ranges mean for a few example lifters. The calculations are ours, applying the reviews' percentages:
| Maintenance intake | 10–20% surplus | Target weekly gain at 0.25–0.5% of body weight |
|---|---|---|
| 2,000 kcal (60 kg lifter) | +200 to +400 kcal | 0.15–0.3 kg |
| 2,500 kcal (75 kg lifter) | +250 to +500 kcal | 0.19–0.38 kg |
| 3,000 kcal (90 kg lifter) | +300 to +600 kcal | 0.23–0.45 kg |
Treat the surplus figure as a starting point and let the weekly trend inform adjustments. If your trend stays well above the target rate for several weeks, the surplus may be bigger than you need. The weekly-gain column applies the novice and intermediate range; advanced lifters were advised to aim lower. Our guide to finding your maintenance calories covers the starting point itself, which is the harder number to get right.
Bigger surplus, more fat: the elite-athlete trial#
The clearest test of "eat more, grow more" came from Norway. Thirty-nine elite athletes added four strength sessions a week to their normal training for 8 to 12 weeks. They were randomized either to a nutrition-counseling group that followed a meal plan designed to create a surplus, or to an ad libitum group that ate as they liked3.
The counseling group ate more, about 3,585 kcal a day against 2,964 (a gap of roughly 620 kcal between groups), and gained more weight: 3.9% of body weight against 1.5%. Fat mass rose about 15% in the counseling group against 3% in the ad libitum group, and the difference in lean-mass gain between groups was not statistically significant. Strength rose similarly in both, and the counseling group's 40 m sprint times got worse.
The trial measured a planned surplus against free eating, not two fixed surplus sizes, and its subjects were young elite athletes. In this trial, eating roughly 600 kcal a day more than the comparison group went with more fat gain and no significant extra lean mass.
Muscle is added at the pace training allows. In these trials, a larger surplus added more fat than muscle.
Lean bulk vs dirty bulk: the small study that found both more muscle and more fat#
One small study compared two surplus sizes directly. In a Brazilian pilot study, 11 male competitive bodybuilders trained six days a week for four weeks. Six ate a high intake (about 67.5 kcal per kg per day) and five a moderate one (about 50.1 kcal/kg/day). For a 90 kg lifter, that is roughly 6,080 against 4,510 kcal a day, by our arithmetic4.
| Outcome over 4 weeks | High intake (n=6) | Moderate intake (n=5) |
|---|---|---|
| Muscle mass (estimated from an equation) | +2.7% | +1.1% |
| Body fat percentage | 16.2% to 17.4% | 13.3% to 13.4% |
This result partly disagrees with the Norwegian trial, since the bigger surplus went with more estimated muscle here. Muscle mass was predicted from an equation that uses body weight, not measured directly, which matters when one group gained more weight. These were competitive bodybuilders on a heavy training volume, in a four-week study with 11 people, published as a pilot in the Journal of Human Kinetics. Slater's review cites it as supporting greater gains with aggressive intake while noting that inferences are "difficult due to methodological concerns"2.
The practical reading: a big surplus may add a little more muscle for lifters with very high training volumes, with more fat gained alongside it.
Slater's review also describes an older overfeeding study in which 12 pairs of identical twins were overfed 4,200 kJ a day (about 1,000 kcal) over a 100-day period while mostly sedentary. They gained an average of 5.4 kg of fat and 2.7 kg of fat-free mass2. A surplus alone does add some lean tissue even without training, but about two-thirds of what they gained was fat.
Protein: the number that matters more than the surplus#
If you are training hard and eating enough protein, the surplus is fine-tuning. The best data on protein is a 49-trial meta-analysis, which found that supplementing protein increased resistance-training gains in muscle mass and strength. Above a total intake of about 1.62 g/kg a day, it found no further gain in fat-free mass, though that breakpoint carries substantial uncertainty5. The details of that threshold and its error bars are in our article on how much protein to build muscle.
Protein also affects what a surplus becomes. In one controlled overfeeding study that Slater's review describes, all groups gained similar fat (about 3.5 kg), but only the two higher-protein groups gained lean mass, about 3 kg. That suggests a surplus without enough protein mostly adds fat2.
When you don't need a surplus at all#
Slater's review notes that younger, less experienced lifters have more potential for muscle growth than experienced ones. That is also why beginners, people returning after a layoff, and people with more body fat can often build muscle while eating at maintenance or even slightly below it. Our explainer on body recomposition covers who can do that and why the scale hides it.
A rough guide to choosing a phase:
- New to lifting, or carrying a lot of body fat: maintenance or a slight deficit can work. Recomposition is realistic.
- Trained for a year or more and fairly lean: a small surplus at the low end of the ranges above, adjusted from your weekly trend.
- Advanced and prioritizing muscle over leanness: a larger surplus may add a little more muscle, with clearly more fat. That's a trade-off, not a free gain.
One more thing: a gaining phase makes the scale go up on purpose. If the fat side of a bulk grows faster than planned, a reasonable adjustment is to trim the surplus and keep training. Our piece on muscle gain masking fat loss explains why scale weight alone can mislead in either direction.
FAQ#
How many extra calories a day should I eat for a lean bulk?#
Reviews suggest a modest surplus: about 10–20% above maintenance in one, roughly 360–480 kcal a day in another (Iraki et al., 2019; Slater et al., 2019), with a target of about 0.25–0.5% of body weight per week for novice and intermediate lifters. Advanced lifters are advised to aim lower.
Does eating more calories build more muscle?#
Only up to a point. In elite athletes, a planned higher intake (about 600 kcal a day more than the comparison group) went with a 15% vs 3% rise in fat mass and no significant difference in lean-mass gain3. A tiny four-week study in bodybuilders found more estimated muscle with a much larger surplus, alongside more fat gain.
Can I build muscle without a calorie surplus?#
Often, yes, especially if you are new to lifting or have more body fat to draw on. Training experience strongly shapes how much muscle you can add, and beginners have the most room to grow2.
Sources#
- Iraki J, Fitschen P, Espinar S, Helms E. Nutrition recommendations for bodybuilders in the off-season: a narrative review. Sports (Basel). 2019. doi:10.3390/sports7070154
- Slater GJ, Dieter BP, Marsh DJ, Helms ER, et al. Is an energy surplus required to maximize skeletal muscle hypertrophy associated with resistance training. Front Nutr. 2019. doi:10.3389/fnut.2019.00131
- Garthe I, Raastad T, Refsnes PE, Sundgot-Borgen J. Effect of nutritional intervention on body composition and performance in elite athletes. Eur J Sport Sci. 2013. doi:10.1080/17461391.2011.643923
- Ribeiro AS, Nunes JP, Schoenfeld BJ, Aguiar AF, et al. Effects of different dietary energy intake following resistance training on muscle mass and body fat in bodybuilders: a pilot study. J Hum Kinet. 2019. doi:10.2478/hukin-2019-0038
- Morton RW, Murphy KT, McKellar SR, Schoenfeld BJ, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018. doi:10.1136/bjsports-2017-097608
Source: BurnWeek — "How big a calorie surplus do you need to build muscle?", https://burnweek.fit/blog/calorie-surplus-for-muscle-gain/. Licensed CC BY 4.0: free to quote or reuse with a link to this page.
