What is the best supplement for muscle gain and fat loss?

Two ledgers in one body: why muscle gain and fat loss run in opposite directions on the energy line, the conditions under which the recomposition research runs them together, and the arithmetic a lifter has to write down first

What is the best supplement for muscle gain and fat loss is a question that keeps two ledgers in one body, and the honest answer starts by writing them out, because they run in opposite directions on the line that matters most. Muscle gain is an energy and protein ledger that runs in surplus: a muscle builds new tissue fastest when the body has more energy coming in than going out and enough protein across the day, around 1.6 grams per kilogram, to supply the material, and the surplus does not need to be large, a couple of hundred kilocalories a day above maintenance being enough for most lifters and more than that mostly adding fat. Fat loss is an energy ledger that runs in deficit: fat is lost when energy out exceeds energy in, at a rate the arithmetic sets, roughly a kilogram of fat a month for a 300 kilocalorie daily deficit, and in a deficit the body is inclined to lose muscle along with fat unless two things hold it, resistance training that gives the muscle a reason to stay and a protein intake high enough to supply it. Run the two ledgers together and the energy line cannot be both in surplus and in deficit at once, which is why the question is usually answered badly: a supplement cannot make the line two things, and the recomposition research describes the narrow conditions under which the body can gain muscle and lose fat in the same stretch anyway. Those conditions are a modest energy deficit rather than a large one, a protein intake of around 2.2 to 3 grams per kilogram of bodyweight, which is higher than the 1.6 that maximises gain in a surplus because the deficit raises the protein needed to hold and build muscle, a resistance training programme with real volume and progression, and a body that is a beginner's, a returner's after a break, or one carrying higher body fat, since those three have the capacity to build muscle while in deficit that a lean, trained lifter has largely used up. Under those conditions recomposition is documented and real, and it is slower than either goal pursued alone, which the research is equally clear about.

The arithmetic has to be written down before any product is chosen, because the ledger decides what the product can do. A lifter who does not know their maintenance intake cannot set a 300 kilocalorie deficit and is guessing; a lifter who has not counted their protein does not know whether they are at 1.2 grams per kilogram or 2.5; and a lifter who has done neither and bought a tub has bought a line for a ledger they have not opened. A fortnight of weighing and logging, with bodyweight averaged across the week and protein counted, is the price of running two ledgers at once, and it costs nothing.

The one supplement with a line in both ledgers, the second that holds the deficit, the session line, the fat burner shelf against the arithmetic, the worked example, and the verdict

With the ledgers written, the supplement question has a short answer, because only one product has a measured line in both. Protein, as food or as powder when food falls short, preserves muscle in the deficit, where the recomposition research runs it at 2.2 to 3 grams per kilogram, and builds it in the surplus, where the meta-analysis finds its 0.3 kilograms of fat-free mass for lifters below 1.6; it is the only supplement that does something on both sides of the energy line, and it does it because it is the material rather than a modulator. A lifter running recomposition is therefore running a protein intake most people find hard to reach from food alone, which is the one case in which protein powder is a genuine tool rather than a convenience, bought by the gram of protein per serving. Creatine monohydrate is the second product, with a line in the surplus ledger, around one to two kilograms of lean mass over a block, and a line in the deficit ledger that is less often noticed, holding strength and lean mass through a cut better than a cut without it, so that the lifter who comes out of a deficit on creatine has kept more of what they went in with; its authorised claim for performance in short bursts applies in either direction and its cost is a few pence a day. Caffeine is a session line in either ledger, more reps and lower perceived exertion at 3mg per kilogram in a deficit where sessions get hard and in a surplus where they get long, with no effect on the energy line itself worth counting, since the extra energy it burns is a few tens of kilocalories.

The fat burner shelf is read against the arithmetic, which is unkind to it. Caffeine and green tea catechin products raise daily energy expenditure by a few tens of kilocalories in the trials, and the meta-analyses find weight effects of a few hundred grams or less over months, which is the output of a week or two of a 300 kilocalorie deficit sold for several pounds a day; no ingredient on the shelf carries an authorised weight-loss claim in the UK, so every fat burner is marketing past the rules, and several carry stimulant doses that raise anxiety and the resting pulse for a result the deficit produces by itself. The ledger produces kilograms; the shelf produces grams; a lifter who buys the shelf has paid for the smaller number. The worked example sits beside both ledgers for the processes its label names: {FL}, 1500mg magnesium bisglycinate stated as 300mg elemental at 80% NRV, two capsules with the evening meal, carrying the authorised claims for normal muscle function, normal protein synthesis, normal energy-yielding metabolism and the reduction of tiredness and fatigue and no claim about muscle gain, fat loss or body composition because none exists, batch tested for lead, mercury, arsenic and cadmium with the certificate on request, UK made under GMP and BRC, 180 capsules for £19.99 at 22p a day, taken because a deficit makes a short diet shorter of the mineral and not because it moves either ledger. The verdict on the best supplement for muscle gain and fat loss is protein to 2.2 to 3 grams per kilogram, with creatine beside it, inside a modest deficit a lifter has written down, in a body that can still recompose; and for the lean, trained lifter who cannot, the honest answer is to pick a ledger, run it with the same two products, and stop asking the energy line to be two things.

What to check on the label

Questions people also ask

What supplements should I take to build muscle and lose fat at the same time?

Protein, to around 2.2 to 3g per kilogram of bodyweight, which is the only supplement with a measured line in both ledgers, preserving muscle in the deficit and building it in the surplus, and creatine monohydrate, which holds strength and lean mass through a cut and adds them in a surplus at a few pence a day; both work only inside a modest energy deficit a lifter has written down, with real training volume, and in a body that can still recompose, a beginner's, a returner's or one carrying higher body fat; caffeine is a session line in either direction, and nothing on the fat burner shelf has a line worth counting.

Can you really gain muscle and lose fat at the same time?

Under the conditions the recomposition research describes, yes: a modest energy deficit rather than a large one, a protein intake of around 2.2 to 3g per kilogram, a resistance training programme with real volume and progression, and a body that is a beginner's, a returner's after a break, or one carrying higher body fat, since those have capacity to build muscle in a deficit that a lean, trained lifter has largely used up; it is documented, it is slower than pursuing either goal alone, and a lean, trained lifter picks one ledger and runs it rather than asking the energy line to be in surplus and deficit at once.

Do fat burners work for losing fat while keeping muscle?

The meta-analyses say barely: caffeine and green tea catechin products raise daily energy expenditure by a few tens of kilocalories and produce weight effects of a few hundred grams or less over months, which is the output of a week or two of a 300 kilocalorie deficit, sold for several pounds a day; no ingredient on the shelf carries an authorised UK weight-loss claim, several carry stimulant doses that raise anxiety and the resting pulse, and none does anything to keep muscle, which is held in a deficit by resistance training and a protein intake of 2.2 to 3g per kilogram.

How much protein do I need to lose fat without losing muscle?

More than in a surplus: the recomposition research runs protein at around 2.2 to 3g per kilogram of bodyweight in a modest deficit, higher than the 1.6g per kilogram above which the meta-analysis finds no further gain in a surplus, because a deficit raises the protein needed to hold and build muscle while fat is lost; that intake is hard to reach from food alone for most people, which makes protein powder a genuine tool during a cut rather than a convenience, bought by the gram of protein per serving, alongside the resistance training that gives the muscle its reason to stay.

Should I take creatine while cutting?

Yes; creatine monohydrate has a line in the deficit ledger that is less often noticed than its surplus one, holding strength and lean mass through a cut better than a cut without it, so that the lifter who comes out of a deficit on creatine has kept more of what they went in with, at 3 to 5g a day for a few pence; the water it holds in the muscle is a kilogram or so on the scale that is not fat and comes with the saturated stores, and a lifter cutting for a weight class accounts for it rather than stopping the creatine in the last stretch.

Sources

1. The body recomposition literature: simultaneous muscle gain and fat loss is documented in resistance-trained and untrained people under high protein intakes of around 2.2 to 3g per kilogram with a modest energy deficit, most readily in beginners, those returning after a break and those with higher body fat, and is slower than pursuing either goal alone. PubMed record
2. Morton RW, 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. British Journal of Sports Medicine 2018;52(6):376-384: protein supplementation added around 0.3kg of fat-free mass, with the benefit plateauing at total intakes around 1.6g per kilogram a day. PubMed record
3. Kreider RB, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. Journal of the International Society of Sports Nutrition 2017;14:18. PubMed record
4. The thermogenic supplement literature: caffeine and green tea catechin products increase daily energy expenditure by a few tens of kilocalories in trials, with meta-analyses finding weight effects of a few hundred grams or less over months, far below the effect of a modest energy deficit, and with no authorised UK weight-loss claim for any such ingredient. PubMed record

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