Eat Less Protein to Grow More


How much protein should you eat? This is one of the oldest and most-contested questions in fitness. Classical bodybuilding advice suggests we should eat at least a gram of protein per pound of bodyweight a day. This makes sense at first, seeing as you need protein to build muscle, but the reality is a little more complicated.

Let’s start with a crude analogy. Let’s say you’re building a house and want to get it finished faster. You have enough materials on-site to keep you going for a while, though not necessarily to finish. Which will let you get it done sooner – getting more materials in now or getting more guys to come and work and buying the rest of the materials later?

Your body tissues are composed of proteins – we all know this. You can’t build body tissues with carbohydrate and fat because neither of those contain nitrogen atoms. We need nitrogen atoms to build complex, stable structures. Proteins are made of chains of amino acids, small molecules with a carboxyl (carbohydrate-like) group and a nitrogen atom.

Back at university I remember one of the PhD students in the physiology lab remark that net muscle protein synthesis in healthy men tops out at around 10 grams per day. I’ve since tried to find the source he was referring to, with no luck. However it stands to reason: if you take out fat gain, a typical rate of muscle gain for an unassisted man is a few (1-5) kilos a year. Anything more than 5 is highly unusual, and 5 itself is very high. Five kilos per year represents 13-14 grams per day.

My point here is that the excess protein mass you need to take on board – because you can’t create matter from nothing and you can’t make amino acids from carbs or fat (not without other amino acids, anyway) – isn’t huge. Certainly the difference between eating 200 g of protein a day and 300 g seems insignificant when the net protein mass needed is on the order of 10 g. Now obviously, this doesn’t account for the fact that protein is being shuttled in and out of body tissues all the time. This is why the RDA of protein for a person not gaining muscle is more than zero grams (!).

This isn’t just theoretical either – by the end of the 90s we had good data on how much protein is needed by different athletes. The best-known work (to anyone who, like me, has studied sport science) was done by Tarnopolsky (famously in 1992 in JAP), using nitrogen balance, and Lemon’s later review of Tarnopolsky’s and other papers. The upshot of these was that although protein requirements to maintain positive nitrogen balance (more nitrogen staying in the body than leaving) increase with hard exercise, it’s not by as much as people on the internet might think. It’s worth noting there has never been a dose-response relationship shown between nitrogen balance and muscle protein synthesis: i.e. more intake above the requirement for positive balance doesn’t increase rate of muscle gain. Interestingly, hard endurance exercise increases protein needs by nearly as much as bodybuilding does. For both, the maximum needs reported are under 1.6-1.7 g/kg per day. The old recommendation of 1 g/lb per day isn’t far off, as that would be 2.2 g/kg per day.

There are problems with nitrogen balance as a measure, but it serves our purpose well enough if we add a safety margin on. If we recommend 1.8 g/kg per day for anyone who lifts weights, we’re recommending plenty. This is especially generous when you consider that whenever needs as high as 1.6-1.7 g/kg per day have been reported, it’s with huge training loads – 12+ hours of hard endurance or resistance training per week by trained athletes. These loads are definitely higher than those performed by recreational bodybuilders or gym rats, who would therefore need even less.

Another aspect to protein that’s overlooked is its inefficiency as a fuel. This is a double-edged sword. Briefly, the uric acid cycle is a process that runs in tandem with the Krebs cycle, the cycle that makes most of the energy in muscle: products from one enter the other and vice-versa, although they occur in different tissues. Nitrogen is unreactive, which makes it hard to remove from wherever it is. It’s therefore difficult to turn an amino acid molecule into a carbohydrate/fat-like molecule (acetyl coenzyme A, for use in the Krebs cycle) that’s useful for fuel. This is why dietary protein contains 6-8 kcal/g but we can only extract 4 kcal/g at best. If you eat large amounts of protein, the body has to get rid of lots of nitrogen – this is the basis of the pervasive bad-for-your-kidneys myth. This isn’t true, but it is true that you’re wasting calories from other food you eat in order to process any protein over your structural requirements.

Protein is also filling, and difficult to eat lots of. For this reason it’s great to eat lots of protein on a caloric deficit – especially because the increased protein helps you hang on to muscle as you lose fat – and a bad idea to eat lots during a surplus. To return to our worker/materials analogy, building new tissue requires raw materials and lots of energy. It’s more efficient to get this energy from other nutrients: namely carbs and fat. It’s easy to eat loads of calories in carbs and fat, and no more effective to eat them in extra protein instead, so make it easy for yourself. It also makes sense with our 1.8 g/kg figure: as you increase your intake of calories, your protein intake stays the same, because it’s scaled to bodyweight. If you weigh 100 kg, you’ll eat 180 g of protein a day whether you’re eating 2800 calories, to lose fat, or 4000, to gain muscle (numbers are approximate). All of those 1200 extra calories therefore come from carbs and fat.

A final word on protein supplements – it is true that research has found the existence of an “anabolic window” after resistance training, during which protein consumption has a strong effect on muscle protein synthesis. However this window is 48 hours long, not 30-90 minutes, and nobody who goes to the gym has more than two days’ gap between meals. Particular benefits of protein shakes, rather than foods containing protein, haven’t been established, other than being convenient. Convenience is enough reason for me to use them – it’s hard to cook a steak at the gym, and if you’re on a surplus you need all the chances you can to cram in more food.

Practical Message

Ultimately my point is that it’s difficult to eat enough to grow consistently. It’s especially hard if you stick to a dogmatic view of protein. If by reducing your relative protein intake (to ~1.8 g/kg/day) you can eat more total calories, you lose nothing and make more gains. And if I care most about two things, they’re getting more for your effort and making more gains.