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High-protein or high-carb: Will either boost your fitness?

A man makes a protein shake in a kitchen

Whether you鈥檙e an occasional gym goer, exercise enthusiast or professional athlete, you鈥檝e probably received tips on how changing your diet could boost your fitness. You might be tempted by high-protein products to build strength, or to reduce your carb intake in order to improve performance. Or the opposite, you might consider 鈥榗arb loading鈥 before a sporting event and consuming further carbs during the event in the hope they鈥檒l fuel and power you through.

Advice for diets aimed at supporting exercise often falls into one of these two camps:

  • Low carb + fat + protein 鈥 to help build and repair muscle while burning fat
  • Carb-led + low fat 鈥 to give you the energy to perform well without taking on extra fat.

But is one really better than the other?

How much protein and carbohydrate should we consume?

A fitness time table for diet

鈥淒ietary guidelines recommend around (one-third of the food you eat) should come from carbohydrates 鈥 these are found in starchy foods, such as bread, pasta, rice, couscous, potatoes, breakfast cereals, oats and other grains like rye and barley. Wholegrain or higher-fibre varieties should be chosen where possible鈥, says nutrition scientist and British Nutrition Foundation spokesperson, Sarah Coe.

As for protein? 鈥淎dults need around 0.75g protein per kilogram of body weight per day. If you are regularly active, you may need slightly more protein to help with muscle growth and repair鈥, says Coe.

However, as you鈥檇 imagine, things start to change when you鈥檙e a sports professional. 鈥淭he exact amount of carbohydrate or protein an athlete needs varies individually, depending on their sport, training programme, and intensity and duration of exercise sessions. An athlete training for three to five hours per week is recommended to have 4鈥5g carbohydrate per kilogram of body weight per day, whereas an athlete who trains much more intensively for at least two hours a day will need double this amount.

鈥淭he protein requirements of strength and endurance athletes are higher than those of the general population. Strength athletes typically require 1.2鈥1.7g protein per kilogram of body weight per day, whereas endurance athletes need 1.2鈥1.4g protein per kilogram of body weight per day鈥, she says. This is because protein contains amino acids, which are the building blocks for muscle growth.

Professional athletes versus the rest of us

Eliud Kipchoge after running a sub-two hour marathon
Image caption,
Kenyan long-distance runner, Eliud Kipchoge, after running a sub-two hour marathon.

The recommended dietary differences between athletes and well, everyone else, is something Dr Michael Newell, Sport and exercise nutrition lecturer at University of Westminster, discusses.

鈥淭hey鈥檙e the physiological weirdos of this world鈥, says the School of Life Sciences professor. He isn鈥檛 being critical of the world鈥檚 leading endurance athletes, in fact the opposite. He鈥檚 explaining how, when it comes to elite performers and their diet, often their biological make-up is different from that of the rest of us.

鈥淓ndurance athletes have been selected for the sport because they鈥檙e very good at it and also because they are exceptionally good at consuming high rates of carbohydrates 鈥 those two things need to go together. You don鈥檛 get an elite marathon runner who can鈥檛 consume carbohydrates at a high rate鈥, he says.

Dr Michael highlights record-breaking marathon runner Eliud Kipchoge as an example of a person鈥檚 physiology being different from the grand majority of others. 鈥淗is aim was to consume around 90g of carbohydrate per hour (during a marathon). Most people would be violently sick if they tried to do that.鈥

As Coe says, prescribed amounts of protein and carbohydrate can differ depending on the person鈥檚 sport and weight. This inevitably means diets differ, even within the .

While professional athletes have nutritional advice prescribed to them and their physiological make-up examined in great detail, this probably isn鈥檛 something the average gym-goer will have access to. Which can lead to problems鈥

Choosing the right diet

Competitive endurance runner and sports dietitian, Alexandra Cook.
Image caption,
Competitive endurance runner and sports dietitian, Alexandra Cook.

Alexandra Cook is a competitive endurance runner and sports dietitian. Rather than suggesting clients take on extreme diets that either focus on carbs or protein, she prefers a more balanced approach. 鈥淭here鈥檚 a huge amount of misinformation out there. We鈥檙e in a world where there are a lot of influencers and people tend to look at what other people are doing and think, 鈥榠f it鈥檚 worked for you, it鈥檚 going to work for me鈥欌, she says.

Cook finds herself having to battle misinformation about certain diets 鈥 especially ones that are restrictive. 鈥淪ome athletes 鈥 especially in the ultra-endurance world 鈥 do tend to go for this low-carb approach and it works for them, which is great. But then they say 鈥榳hen I鈥檓 up and running, I鈥檝e never felt fitter鈥. That doesn鈥檛 mean it鈥檚 going to work for everybody else. I know for sure if I cut out carbohydrates, I probably wouldn鈥檛 be able to get out of bed, let alone run a 50-mile race.鈥

So Cook鈥檚 approach is to instead tweak the guidelines to the individual she鈥檚 working with, 鈥渟o that it accounts for their sport or for personal reasons such as different tastes and requirements.鈥

This means no extremes of either protein or carbs.

This balanced approach is something Dr Newell agrees with. 鈥淚f you want to be able to train consistently, it would be ridiculous to exclude any macro-nutrient, in my opinion. To put it simply, you need carbohydrates to sustain longer, high-intensity training, and you need protein to help recover from that and to replace amino acids you鈥檝e lost. On top of that, you need a bit of fat in order to ensure you get an adequate number of calories in your diet.

鈥淭his isn鈥檛 particularly exciting or novel, it鈥檚 the advice. There鈥檚 a tendency for the newest-best-thing to be the diet you should be doing. But actually, there鈥檚 usually limited evidence behind whether they are attainable and have the results people think they do鈥, he concludes.

Do we really need lots of protein?

A woman who's just done exercise eats a banana and drinks water in a kitchen

鈥淧rotein is a big sports nutrition product at the moment, so I encourage people to look at who鈥檚 pushing it and why. Of course, protein is a very important nutrient, it鈥檚 vital for helping us perform and get the best out of ourselves鈥, says Cook.

鈥淚t also helps us repair and recover. But currently people are being led to think they need an extortionate amount. The reality is, if we take on more protein than our body needs, we鈥檒l just excrete it out.

The sports dietitian continues: 鈥淩ecently I kept a food diary, just out of interest, to see how much I was consuming. Without thinking, I was eating enough protein. This is simply because most people who train regularly eat a greater volume of food overall, so most reach their protein requirements and more without even trying.

鈥淚f you have a portion of protein at each meal, and if you鈥檙e doing slightly higher training loads you get protein from snacks like nuts, peanut butter and milk, you鈥檒l easily meet your protein requirements.鈥

Coe also emphasises this point: 鈥淚t鈥檚 a myth that eating lots of extra protein equals bigger muscles. While protein supplements are popular among some gym-goers for muscle building, they are generally unnecessary as most active people can easily get enough protein from a healthy, varied diet, including high-quality, lean protein foods.鈥

What about if you鈥檙e following a vegan diet?

Forest Green Rovers players celebrate a goal

Anyone who watched the documentary The Game Changers will have seen vegan athletes and experts talking about how following a vegan diet and performing to a high standard go hand in hand. They advocate taking on both plant-based .

While the documentary has faced , it does highlight that there鈥檚 a seemingly growing community of professional . How does this work in practice?

Tom Huelin is the fitness coach for League Two鈥檚 Forest Green Rovers 鈥 the 鈥榳orld鈥檚 first 100 percent鈥. As part of his responsibilities, he gives nutrition advice to the team.

While the players are in control of their own meals at home, at work they follow a vegan diet and there are 鈥渁 lot of vegetarians and a couple of vegans鈥 in the squad.

However, being a vegan club doesn鈥檛 make the nutritional requirements different from those of any other team. Tom explains that both protein and carbs in particular are a big focus for the footballers鈥 requirements. And the amounts prescribed depend on the football schedule.

鈥淔ootball鈥檚 a results business, and the most important time to be nutritionally prepared is on match day. So you just start with that and work backwards into the training days to make sure you鈥檙e at your optimum on match day鈥, Huelin says, before explaining what each day needs to include.

The basics are: on the days they鈥檙e going to be working harder they consume more carbs, and they make sure after intensive sessions they receive a top-up of protein to help with muscular fatigue. To help encourage the team to receive the correct nutrition when they鈥檙e off the clock, they have access to an online resource which includes recipes for vegan meals.

鈥淭he vegan element of it is key. We can attribute lots of positive things to it 鈥 physically and in terms of the levels of recovery. Players are feeling less fatigued. These are anecdotal of course, so while it might be they get these effects from following (at least) a semi-plan-based diet, we don鈥檛 know for sure鈥, the fitness coach says.

Is it a challenge to get all the right nutrients into the players on a vegan diet? 鈥淣o, and that鈥檚 because there are now good vegan plant protein supplements. It wasn鈥檛 always the case. When I first joined the club, I found it really tricky to get something that had a sufficient amount 鈥 and the right type 鈥 of protein. In the last four years though, as veganism has become fashionable, more and more sports nutrition brands are developing vegan protein products. And we use things like soy milk, which is really high in protein.鈥

So will one diet improve your fitness levels?

Kind of. While there鈥檚 research to support the view that could help athletes, there鈥檚 also plenty pointing to the opposite, that low-carb diets will .Does that mean carbs win the race? They鈥檒l definitely give you the fuel you need to compete, but you do need protein with comprehensive amino acids to repair and help build your lean muscle mass.

The experts we spoke to all advocate that it鈥檚 preferable to not cut any macro-nutrients out of your diet and to follow healthy eating guidelines 鈥 adapting them depending on your individual demands rather than re-writing them entirely. So, combined protein, carbohydrate and even fat should all help you cross that finish line 鈥 but unless you鈥檙e an elite athlete, you鈥檒l almost certainly get enough of these from a healthy diet.