Calorie Surplus for Muscle Gain: How Much Is Enough?

Why nobody can tell you the right calorie surplus

Most surplus advice works backwards from the tissue. Decide how much muscle you hope to gain in a month, multiply by the energy stored in it, and divide by thirty. A 2019 review led from the University of the Sunshine Coast and the Australian Institute of Sport lists what that leaves out: the energy it costs to build the tissue in the first place, the way the body adjusts when you eat more, and differences in training experience and starting point. The authors write that these estimates have never been validated in people who do resistance training, and that the specific surplus needed to build muscle is unknown.¹

The same review also says there is clear evidence that a surplus is anabolic, even without training.¹ Eating more helps, then. The open question is how much more before the extra stops being muscle, and only a handful of trials have given people different amounts to find out. All of them are small.

Five percent against fifteen, in people who already lift

The closest test is a 2023 trial from Auckland University of Technology. Twenty-one lifters with at least a year of training behind them were randomised to eat at maintenance, 5% above it or 15% above it for eight weeks, while doing three supervised full-body sessions a week. COVID-19 delays and dropouts left 17 who finished.²

The groups did not eat what their labels say. In the intake figures the paper reports, daily calories went up by 169 in the maintenance group, 489 in the 5% group and 719 in the 15% group. Body weight rose by 0.4 kg at maintenance and by 3.3 kg in both surplus groups. The authors say plainly that, despite consistent monitoring, not every participant followed the surplus they were assigned.² I think that is the most useful number in the paper. People who logged every meal in a food tracking app and checked in with a researcher every week, told to eat a small surplus, gained weight as fast as the people told to eat a large one.

Compared as randomised, the results were mixed. There was no evidence the groups differed in muscle thickness or squat strength. The 15% group improved its bench press more than the other two, and there was moderate evidence that it gained more skinfold thickness than the maintenance group, with weak evidence that the 5% group did too.²

Because the groups had blurred into each other, the authors also looked at the actual weight change of all 17. Weight gained strongly predicted skinfold gain and only weakly predicted growth in the biceps, the muscle the programme worked hardest. Their conclusion is that faster weight gain, and by proxy a larger surplus, mainly raises the rate of fat gain rather than adding strength or muscle. They limit it to what they studied: lifters of mixed experience doing moderate volume three days a week for eight weeks.²

What the extra calories became in athletes and bodybuilders

A Norwegian trial gave 39 elite athletes, average age about 19, an 8 to 12 week weight-gain period with four extra strength sessions a week on top of their sport. About half followed a meal plan built to keep them in a surplus and the rest ate as they liked. The meal-plan group ate more, 3,585 calories a day against 2,964, and gained more weight, 3.9% against 1.5%. The difference was fat. Fat mass rose 15% in the meal-plan group and 3% in the other, and the gain in lean body mass was not different between them. One-rep maximums rose by 6 to 12% in both groups.³

A Brazilian pilot study found a muscle difference, in a group where you would least expect to see one. Eleven competitive male bodybuilders trained six days a week for four weeks, eating either about 67.5 or about 50.1 calories per kilogram of body weight a day. Muscle mass went up in both groups, by 2.7% on the higher intake and 1.1% on the lower one, and body fat went up by 7.4% against 0.8%.⁴ Eleven people over four weeks is a pilot, which is what the authors call it. It still shows the trade in its plainest form: the bigger surplus bought a little more muscle and a lot more fat.

Who might get more from a bigger surplus

One older trial reads like a counterexample. Seventy-three men on an eight-week programme of four training days a week were given a 2,010-calorie supplement on top of their normal diets, either carbohydrate with protein or carbohydrate alone, or no supplement. Both supplemented groups gained 3.1 kg, and nearly all of it was fat-free mass: 2.9 kg with the protein supplement and 3.4 kg with carbohydrate alone. Strength rose in all three groups and did not differ between them.⁵ The Auckland authors describe these men as untrained and treat the result as the starkest contrast to their own.²

I would not lean on it. The arithmetic does not close: 2,010 extra calories a day for eight weeks is over 100,000 calories, the paper reports no difference in what the groups ate apart from the supplement, and yet the men gained about 3 kg. Either a lot of the supplement was not drunk or the food records missed something. And fat-free mass counts everything that is not fat, including water and stored carbohydrate, which can move a reading by as much as weeks of real change, as the body recomposition post explains.

What the Auckland authors take from it, along with their own data, is a hypothesis: less-trained people may be able to use a bigger surplus, and experienced lifters should use a smaller one.² An off-season review by some of the same researchers turns that into a recommendation, which I come back to below.⁹ I could not find a trial that put beginners and experienced lifters on the same surplus and compared what they gained. It is the same gap the body recomposition post ran into from the deficit side.

The same 1,000 extra calories, very different gains

Even with the calories fixed by researchers, people do not gain the same. In a study at Laval University, 12 pairs of identical twins, all young men, were overfed by 1,000 calories a day, six days a week, for 84 days out of 100. That is 84,000 extra calories each. The average weight gain was 8.1 kg, and the range ran from 4.3 to 13.3 kg. Twins resembled each other, with about three times more variation between pairs than within them, which the authors read as genes influencing whether surplus energy is stored as fat or as lean tissue.⁶

A Mayo Clinic study found where some of that difference goes. Sixteen non-obese volunteers ate 1,000 calories a day over their maintenance needs for eight weeks. Two-thirds of the rise in their daily energy expenditure came from non-exercise activity, the fidgeting, standing and moving about of ordinary life, and changes in it accounted for the tenfold differences in how much fat people stored.⁷

Nobody in either study was lifting, so neither says anything about muscle. What they do show is that a surplus on paper is not the surplus your body ends up storing. Two people logging the same 300 extra calories can be gaining at quite different rates, which is why the plan further down sets the surplus from the scale and not from the calculator.

Protein decides what a surplus builds, not how much fat

A trial at Pennington Biomedical kept 25 healthy adults on a metabolic ward and overfed them by about 40%, around 954 calories a day, for eight weeks, on diets with 5%, 15% or 25% of calories from protein. Nobody was training. The low-protein group gained less weight, 3.16 kg against 6.05 and 6.51 kg. Body fat, though, rose by a similar amount in all three groups and made up 50% to more than 90% of the extra calories stored. The difference was lean body mass, which rose by 2.87 kg on the 15% diet and 3.18 kg on the 25% diet and did not rise on the 5% one. The authors conclude that calories alone accounted for the increase in fat, while protein affected energy expenditure and the storage of lean mass.⁸

For anyone tracking macros in a surplus, that splits the job in two. How big the surplus is decides how much fat you gain. Protein decides whether anything else comes with it. The off-season review recommends 1.6 to 2.2 g of protein per kilogram of body weight a day for natural bodybuilders.⁹ Why calculators disagree about the exact figure, and why the curve flattens out, is the subject of why macro calculator apps disagree about your protein target.

What the evidence does not settle

• The size of the surplus. The 2019 review calls it unknown, and the one trial that compared surplus sizes in trained lifters ended with 17 people whose intakes did not match their groups.¹²
• Whether training experience changes the answer. It is the basis of the current recommendations, but nobody has tested it head to head.²⁹
• Women. The bodybuilders, the men on the supplement and the twins were all male, so these studies say little about how women respond to a surplus.⁴⁵⁶
• Anything past three months. The training trials ran four to twelve weeks. Whether the extra fat from a larger surplus is a fair price over a year or more of training, they cannot say.
• How independent the sources are. Several of the same researchers wrote the 2019 review, the 2023 trial and the off-season review, so they agree with each other more than three unrelated sources would.¹²⁹

What a calorie counter app can see on a bulk, and what it cannot

MyPlate, the app I build, has a gain-weight goal. It estimates your maintenance from your age, height, weight, sex and activity level with the Mifflin-St Jeor equation, sets the calorie target 10% above that, and splits it 25% protein, 49% carbohydrate and 26% fat. Those shares sit inside the ranges the National Academies set for adults.¹⁰ The 10% is the bottom of the off-season review's 10 to 20% range, and inside the 5 to 20% the Auckland authors suggest.²⁹

It does not ask how long you have been training, so the 10% does not shrink for experienced lifters the way both of those sources suggest. It does not recompute the target when you log a weight, so if you gain faster or slower than you meant to, you change the target yourself. It does not know whether you lift. And the calories and macros it shows for a meal are an estimate from a photo or a sentence, with no food database or barcode scanner behind them. Protein is a share of calories rather than a figure per kilogram, which means that on the gain goal it can land above the review's range.

How to set a calorie surplus and check it with the scale

Take the profile the body recomposition post used: a 30-year-old man, 180 cm and 85 kg, moderately active. MyPlate estimates his maintenance at 2,836 calories, and the gain goal sets him at 3,120, a surplus of about 284 calories a day. Protein at 25% comes to 195 g, about 2.3 g per kilogram and a little over the top of the review's range. A 35-year-old woman, 165 cm and 68 kg, moderately active, gets an estimated maintenance of about 2,130 and a gain target of 2,344, around 213 calories over, with 146 g of protein, about 2.1 g/kg.

I am deliberately not turning those surpluses into a weekly weight gain with the 3,500-calorie rule. That rule misleads people losing weight, as the weight loss plateau post explains, and the twins and the Mayo volunteers show how widely real gains scatter around it in the other direction.⁶⁷ Use the scale for that part.

• Find your maintenance first, by watching it rather than calculating it if you can. Two or three weeks of steady eating, daily logging and morning weigh-ins is the method in how to find your maintenance calories.
• Add a modest surplus: 5 to 20% over maintenance, toward the low end the longer you have been lifting.²⁹
• Set the pace from the scale. The off-season review suggests about 0.25 to 0.5% of body weight a week for novice and intermediate lifters, and slower for advanced ones.⁹ For the man above, that is roughly 0.2 to 0.4 kg a week. Compare weekly averages, not single mornings.
• If you are gaining faster than that for three or four weeks running, take some calories out. The Auckland data suggest the extra speed is mostly fat.² If the average has not moved after a month, add a little and give it another few weeks.
• Check protein in grams against your weight, and aim for at least 1.6 g/kg.⁹
• Train, and add weight or repetitions over time. All four training trials above paired the surplus with a resistance programme. In the ward study, where nobody trained, half or more of the stored surplus was fat.²³⁴⁵⁸

If calorie tracking is making you anxious, or you are logging to punish a meal rather than to understand it, stop and talk to a doctor or a registered dietitian. What the research says about who that is most likely to be is in can calorie tracking cause an eating disorder.

Common questions

Gain slowly, and let the scale set the surplus

Whatever surplus you start with is a guess, whether it comes from a calorie counter app or from this page, and the trials say a guess on the high side gets paid for mostly in fat.²³ Start small, get the protein in, train, and adjust the calories from what your weekly average weight does.

Sources

1. Slater GJ, Dieter BP, Marsh DJ, Helms ER, Shaw G, Iraki J (2019). Is an energy surplus required to maximize skeletal muscle hypertrophy associated with resistance training. Frontiers in Nutrition, 6:131. Read on PubMed →
2. Helms ER, Spence AJ, Sousa C, et al. (2023). Effect of small and large energy surpluses on strength, muscle, and skinfold thickness in resistance-trained individuals: a parallel groups design. Sports Medicine - Open, 9(1):102. Read on PubMed →
3. Garthe I, Raastad T, Refsnes PE, Sundgot-Borgen J (2013). Effect of nutritional intervention on body composition and performance in elite athletes. European Journal of Sport Science, 13(3):295-303. Read on PubMed →
4. Ribeiro AS, Nunes JP, Schoenfeld BJ, Aguiar AF, Cyrino ES (2019). Effects of different dietary energy intake following resistance training on muscle mass and body fat in bodybuilders: a pilot study. Journal of Human Kinetics, 70:125-134. Read on PubMed →
5. Rozenek R, Ward P, Long S, Garhammer J (2002). Effects of high-calorie supplements on body composition and muscular strength following resistance training. Journal of Sports Medicine and Physical Fitness, 42(3):340-347. Read on PubMed →
6. Bouchard C, Tremblay A, Després JP, et al. (1990). The response to long-term overfeeding in identical twins. New England Journal of Medicine, 322(21):1477-1482. Read on PubMed →
7. Levine JA, Eberhardt NL, Jensen MD (1999). Role of nonexercise activity thermogenesis in resistance to fat gain in humans. Science, 283(5399):212-214. Read on PubMed →
8. Bray GA, Smith SR, de Jonge L, et al. (2012). Effect of dietary protein content on weight gain, energy expenditure, and body composition during overeating: a randomized controlled trial. JAMA, 307(1):47-55. Read on PubMed →
9. Iraki J, Fitschen P, Espinar S, Helms E (2019). Nutrition recommendations for bodybuilders in the off-season: a narrative review. Sports, 7(7):154. Read on PubMed →
10. Institute of Medicine (2005). Acceptable Macronutrient Distribution Ranges, in Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. The National Academies Press. Read the report →

The formulas and limits behind MyPlate's own numbers, with their citations, are on the health sources page.