Is this an argument that you cannot build muscle at all (or even maintain it) without being in calorie surplus.
I accept that protein is necessary, perhaps exercise is the most important, but I am not persuaded that calorie surplus is essential and otherwise there cannot be any building of muscle.
I thought I would ask chatGPT. Sadly for some reason it would not produce a share so I have to copy all of the response:
chatGPT said:
The research answer is: no, a calorie surplus is not strictly required to increase muscle mass, but it often makes muscle gain easier and may help maximize it in some people. The strongest overall reading of the literature is:
- Muscle gain is possible at maintenance calories or even in a deficit
- this is more likely in beginners, people with higher body fat, and people eating plenty of protein
- larger or prolonged deficits reduce lean-mass gains on average
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large surpluses tend to add more fat, and the muscle advantage is often smaller than people expect (PubMed)
A useful distinction is possible versus optimal. A 2019 review on this exact question concluded that the specific surplus needed to optimize hypertrophy is still unknown, and textbook surplus recommendations have not really been validated well in resistance-trained people. The same review also noted that an energy surplus is anabolic, but the evidence does not show a clear, universally required surplus for hypertrophy in all situations. (PubMed)
There is also direct evidence for body recomposition. In a randomized trial, young men doing hard training while eating a marked energy deficit still gained lean body mass when protein was high: the high-protein group gained about 1.2 kg LBM over 4 weeks despite the deficit, while also losing more fat. That shows muscle gain can occur without a surplus under the right conditions. (PubMed)
That said, deficits do seem to hurt gains on average. A meta-analysis by Murphy and Koehler found that energy deficiency impairs lean-mass gains but not strength gains, and their meta-regression suggested that deficits of roughly 500 kcal/day were enough to prevent lean-mass gains on average in the included studies. Their practical conclusion was that people trying to build lean mass should avoid prolonged energy deficiency, and those dieting should try to avoid deficits larger than about 500 kcal/day if preserving or gaining muscle is a priority. (PubMed)
The people most likely to gain muscle without a surplus are the groups repeatedly highlighted in the literature: resistance-training novices, and overweight or obese individuals. The 2019 review explicitly states that hypertrophy in an energy deficit seems more likely in these groups. A separate systematic review in people with overweight/obesity found that resistance training plus caloric restriction was generally good for fat loss and tended to maintain lean mass rather than increase it, whereas resistance training alone was better for increasing lean mass. So recomposition is real, but in larger populations it often looks more like fat loss with muscle preservation, not massive muscle gain. (PMC)
Studies in trained lifters suggest the benefit of “bulking harder” is limited. In a 2023 trial of resistance-trained individuals, people consuming larger surpluses gained similar increases in strength and most measured muscle thicknesses, but gained more skinfold thickness/body fat. The authors’ summary was that the clearest and strongest effect of a larger surplus was more body fat, with only weak evidence of extra hypertrophy in one heavily trained muscle group. (PMC)
There is also a small pilot study in competitive bodybuilders showing that the higher-energy group gained more muscle than the moderate-energy group over 4 weeks, but they also gained more body fat. So a surplus may help in trained people pushing for maximum mass, but the trade-off is usually extra fat gain, and the evidence base is still fairly thin. (PMC)
Protein matters a lot here. The ISSN position stand says 1.4–2.0 g/kg/day is sufficient for most exercising individuals for building or maintaining muscle, and higher intakes may be especially useful during calorie restriction. In practice, many sports-nutrition reviews now place hypertrophy-focused intakes around 1.6–2.2 g/kg/day, especially when calories are not generous. (Scholar Commons)
So the best plain-English conclusion is:
You do not need a calorie surplus to gain some muscle.
But if your goal is maximal muscle gain, especially if you are already fairly lean and well trained, a small surplus is usually the safer bet than maintenance or a deficit.
If you are newer to training, carrying more body fat, and eating enough protein, you can often gain muscle without a surplus and sometimes even while losing fat.
What the literature does not support well is the idea that a large surplus is necessary; that mostly seems to raise fat gain. (PubMed)
A practical evidence-based summary would be:
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Beginner / higher body fat: muscle gain at maintenance or modest deficit is realistic. (PMC)
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Intermediate / advanced / lean: a small surplus is more likely to maximize gains. (PubMed)
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Large surplus: usually more fat, unclear extra muscle benefit. (PMC)
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Aggressive deficit: tends to blunt lean-mass gains. (mediaTUM)
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High protein + resistance training: essential either way. (PubMed)
If you want, I can turn this into a table of the main studies with their findings and limitations.