Dr Jose Antonio is CEO and co-founder of the International Society Of Sports Nutrition and assistant professor of exercise and sports science at Nova Southeastern University in south Florida.
When we talk about ‘high-protein’ diets the first thing we have to do is actually define what such a diet is. If you look at the existing scientific literature it can be very misleading because if someone’s daily intake of dietary protein is higher than the recommended daily amount, then it’s instantly classed as a ‘high-protein’ diet.
In the US the recommended daily allowance (RDA) of protein is 56g. The UK’s NHS recommends an RDA of 50g, while the British Nutrition Foundation makes it more individualised by recommending 0.75g of protein per kilogram of bodyweight per day, which works out at 60g for an 80kg man.
I’ve heard claims that eating 1.2g of protein per kilo constitutes a high-protein diet or that if protein makes up 35% of your daily calorie intake then that’s a high-protein diet too. The problem with using a percentage is that if you are on a very low-calorie diet then it doesn’t matter whether protein intake is 35% or 75% – you won’t be eating very much protein at all.
I was a co-author on the International Society Of Sports Nutrition (ISSN) position stand on protein and after combing the literature the majority of recommendations for daily protein intake falls within the range of 1.5g to 2g per kilo. I don’t think that’s an especially high daily intake. And I guarantee that if you ask anyone who worked on that position paper whether that’s enough they’ll say you need more than that too.
Based on the data I’ve collected – primarily from 18 to 30 year old young men and women who regularly weight train – most have an average intake of at least 2g per kilo. So for me to view a diet as high-protein it must exceed this 2g threshold. We just finished a study where we gave subjects a high-protein diet of up to 3.5g per kilo. We have redefine what ‘high’ is, because the way it’s defined right now is absolutely wrong.
The low recommendations in the literature inspired some recent research projects I’ve conducted at Nova Southeastern University in South Florida. I got thinking about what happens if we give people a lot of protein to eat per day. I didn’t know the answer and I wanted to find out. If 2g per kilo is the ceiling and that’s all you need, then nothing should happen if you go over and above this amount and give them 3g or even 4g per kilo.
There must be hundreds and thousands of studies on every conceivable form of low-calorie diet. Every single variation must have been examined at some point. I want to know what happens when you overfeed subjects. That’s what happens regularly for professional athletes and sportsmen who eat a huge amount of calories per day.
Protein and body fat
It turns out something very significant does happen when you give people more protein and we recently presented our findings at the 12th annual ISSN Conference in Austin, Texas.
In the study we took trained subjects and put them on a periodised, bodybuilding-style body-part split training programme of four to five sessions per week for two months. One group consumed roughly 2g of protein per kilo, and the other group consumed around 3.4g per kilo. Both carb and fat intake was the same for both groups: 1g per kilo and 3g per kilo respectively.
Some people might say we actually therefore had two high-protein groups, according to the widely accepted historic RDAs. But in my mind we had a normal group and a high-protein group. After eight weeks we got some very interesting data. First up, both groups got stronger. Their one-rep maximums on the squat and the bench went up significantly. That wasn’t surprising. But what did come as a very pleasant surprise was the body composition data.
This showed that both groups gained the same amount of lean body mass, about 1.5kg on average. But when we measured fat loss the high-protein group – which ate roughly 400 calories more per day than the normal group, because of the higher protein intake – actually lost significantly more body fat than the group that consumed fewer calories.
So, the high-protein group, which consumed more calories in the form of protein, gained the same amount of lean muscle mass but with the added bonus that they also got significantly leaner, averaging around a 2-3% drop in body-fat percentage.
For most people it’s totally counter-intuitive that eating more total calories per day leads to a reduction in body fat. They can’t get their heads around it because they are so used to hearing and thinking that you need to reduce calories to lose fat. Our results clearly contradict this. To lose body fat do you have to be in a calorie deficit? Well, these subjects were not in a calorie deficit and they did lose weight.
A lot of the subjects found eating that much protein difficult. In fact, I tell people when they volunteer for studies such as this that they better be prepared to work. Eating that much protein is a real effort and it requires a lot of focus and planning. It’s almost like taking on a part-time job.
These aren’t studies where you get to kick back and have a lot of fun eating a lot of food. I had several subjects that complained about being hot. It was like their bodies became a furnace from constantly digesting all the protein.
We set each subject a goal and told them that they needed to hit that number of grams of protein per day. And that’s all we told them. We didn’t care how they reached that target, we only cared that they hit it. They had to figure it out for themselves the best way, or the most sustainable way, for them to eat what they needed to.
Some people would eat real food during then day do a couple of big protein shakes before bed, while others would be eating 40g of protein on the hour, every hour, so they all had different strategies based on what would work best for them. The caveat is that you can’t consume that much protein through just breakfast, lunch and dinner. Everybody had to put shakes in somewhere during their day and had them at the most convenient time.
Eating protein is different to eating carbs and fat because of the thermic effect of protein, meaning your body burns more calories digesting it than it does with the other two macronutrients. What also seems to be the case is that combining higher protein consumption with training then increases the thermic effect of exercise. What’s more, eating a high-protein diet appears to also increase the thermic effect of all non-exercise activity during the day. What this means is that your body is simply burning more calories – and seemingly these calories are coming from existing fat stores – all day long when you eat a high-protein diet.
When you think about it, most of your day is not spent lifting weights. It’s maybe an hour or 90 minutes out of 24 hours, so it’s a small percentage. It’s what you do the rest of the day that has a really big impact on body-fat regulation but a lot of people don’t fully understand or appreciate this.
I also think that there’s something about eating more protein that makes people more active throughout the course of the day. Why that is, I have no idea, but it seems to me that it could be a valid theory for why eating more protein makes you leaner because you move more throughout the day.
The two things I want to prove is that eating a high-protein diet won’t make you fat, and that eating a high-protein diet is safe. We are currently in the middle of a one-year study of trained subjects where we periodise their eating when they go on a high-protein block for eight weeks then a more moderate intake for eight weeks and rotate these two-month blocks for a year. We’re doing it because people don’t eat exactly the same way all year round and there are seasonal differences, vacations, and many other factors that will change how the typical diet looks from one season to the next. By periodising their diet it mimics what happens in real life.
Over the course of the year all of the subjects will be on a high-protein diet when you average it out, and one of our goals is to see whether we can put to rest the notion that eating a lot of protein is bad for you. Does it harm your kidneys or liver? The study we’ve just published found via blood tests that there was absolutely no impact on kidney or liver function from eating more protein – everything stayed exactly the same.
Where did people get this idea that protein is bad for the kidneys? Nutty clinicians saying so doesn’t make it so. There’s no substance to these claims and we’re setting out to prove it.