From protein powders to high-protein breakfast cereals, it seems like protein is everywhere these days. Plus, a lot of popular high-protein diets have been making waves — the macronutrient is central in both keto and paleo plans. It’s also not uncommon for legions of runners to whirl up protein shakes after hard runs. So, are carbs no longer king?

In general, protein is a crucial element of good nutrition. One of the three macronutrients, along with carbohydrates and fat, protein is incredibly important for our health. It’s responsible for several vital functions in the body, including building muscles and bone, regulating acid-base balance, increasing immunity, and it’s involved in the production of essential hormones, antibodies, and enzymes.

The amino acids that make up protein are part of every cell in the body, so it’s no wonder that protein is a part of our daily diet, and it’s a nutrient we can’t live without.

This article takes a deep dive into the advantages and disadvantages of going bigger on protein and helps you determine the right amount of the mighty macro for you.

What It Means to Eat a High-Protein Diet
In general, a high-protein diet is individual but it’s one in which you’re making an effort to eat more protein each day than you normally might and more than what is typically in the standard American diet.

Overall, though, it means making sure to get no less than 30 percent of your total calories from protein. That typically means eating fewer calories from carbohydrates or fats to keep your calorie total in balance. Some diets will encourage an even bigger allotment of daily calories to protein — up to 40 percent of total caloric intake hailing from this macronutrient.

It’s important to know that each gram of protein supplies 4 calories; carbs also have 4 calories, while a gram of fat has 9 calories. So if a runner or other endurance athlete is consuming 2,800 calories a day, then a higher protein eating plan with 30 percent of calories coming from this macro means an intake of 840 calories of protein, or 210 grams.

Following a high-protein diet requires:

• Including eating enough protein at every meal
• Moderating your intake of carbs and fat to allow for the extra calories from protein
• Snacking on protein between meals
• Using protein powders to get enough if you can’t consume the required amounts from whole foods

Some of the best choices for high-protein diets are foods with a higher percentage of their calories hailing from protein. The protein percentage of a food tells you how much protein per calorie it contains. Here are some examples:

• Chicken breast: 75% protein
• Egg: 35% protein
• Greek Yoghurt: 55% protein
• Ground beef, extra lean: 72% protein
• Salmon: 40% protein
• Tofu: 46% protein

1. More Muscle
Many endurance-focused athletes neglect their protein intake, but that can be bad news for their muscles. “Since many endurance sports like running are very catabolic, higher amounts of dietary protein can be beneficial in the maintenance of muscle mass,” says endurance sports dietitian Kyle Van Horn, RDN, owner of FlyNutrition. “So if athletes don’t prioritise eating sufficient amounts of protein then they could be sacrificing some of their muscle, which increases the risk for sports-related injuries.”

In fact, according to research, higher protein intake is considered one of the nutritional strategies for reducing injury occurrence in endurance athletes.

Over the years, studies have shown a higher protein intake can increase muscle size and strength, especially when combined with some form of resistance training. One investigation, published in The American Journal of Clinical Nutrition in 2019, also showed that when people consumed higher amounts of protein when they were performing endurance exercise sessions three times a week, they experienced an increase in lean body mass, as well as a boost to VO2 max.

“Carbs might be what give your muscles the fuel they need to keep you running strong, but it’s the protein that gives your muscles what they need to repair, grow, and get stronger,” Van Horn explains.

2. Stronger Bones
Your bones aren’t built on calcium alone. “You also need sufficient amounts of protein in your diet to help keep your bones strong and break resistant,” Van Horn tells Runner’s World. The protein you eat provides the amino acids necessary for building and maintaining bone tissue.

If you skimp too much on protein in favour of carb-loading, Van Horn suggests that you could be weakening your bones over time, which may set the stage for stress fractures. (Note: Up to this point, there appears to be more research on the importance of eating extra amounts of protein to reduce bone fractures in older adults, rather than athletes, as the former typically eat insufficient amounts of the macronutrient and suffer more bone breaks.)

With this said, there is no proof that very high-protein diets are more beneficial to bone health than more modest intakes that still provide sufficient amounts of amino acids. The most important thing to remember, Van Horn says, is that a combination of a low intake of calories, calcium, and protein is particularly detrimental to bone health in endurance athletes.

3. Better Nutrition
Protein-rich foods include seafood, eggs, meat, legumes, and dairy products. These foods are not only high in protein but high in a range of important nutrients in general. “That means a high-protein diet can also be a high-nutrition diet overall for athletes,” says Van Horn. For example, Van Horn notes that with dairy, you gain a calcium and vitamin D advantage and with meats, there are bioavailable iron and B vitamins.

Certain protein-rich seafood, like salmon and sardines, will also deliver a dose of heart-benefiting omega-3 fats. Plant proteins like tempeh, tofu, and lentils will give you a lift in fibre, vitamins, minerals, and various antioxidants.

People on higher protein diet plans will often not just choose to reduce their overall carbohydrate intake but also limit their consumption of highly processed carby foods like white bread, baked goods, and sugary drinks. While there is a place for these foods in an athletic diet, for the most part, we are better served by eating fewer of them and eating more protein can help accomplish this goal.

A large 2023 study in BMC Medicine shows that greater intakes of more highly processed carbs, like refined grains, can drive up the risk for cardiovascular disease but increased consumption of lesser processed versions, like whole grains, offer protection against the condition.

4. Improved Body Composition
There is a fair bit of scientific evidence that if you need to shed a few pounds or maintain previous weight loss, prioritising protein in your diet can help in this pursuit. There are a few ways eating a greater percentage of your daily calories from protein can lend assist with this goal.

One is the influence the macro has on reducing hunger. “Protein does digest more slowly in the body than carbohydrate, which can modulate blood sugar and keep people fuller longer,” Van Horn explains. “And with more satiety, you have fewer cravings, and are less likely to overeat.”

Protein can increase production of appetite-regulating gut hormones, like peptide YY and GLP-1, both of which help you feel full and satisfied. For some people, this can help better manage overall calorie intake. However, there is some research that suggests that different types of protein can have different effects on satiety.

What’s more: Higher protein eating may also raise a person’s metabolic rate, which can increase the daily caloric burn to make weight loss and maintenance easier. Protein has a higher diet-induced thermogenesis — the production of heat that occurs after eating, which contributes to the body’s resting metabolic rate — than carbs and fat. The increase in protein synthesis in the body that occurs after eating sufficient amounts of protein will also contribute to torching more calories.

Helping to preserve muscle mass, which is more metabolically active than fat mass, during periods of lower-calorie dieting and weight loss makes eating more protein important for keeping up the calorie burn. With this said, it’s still a bit controversial as to what degree of an impact the bump in metabolic rate can have on short- and long-term weight loss.

For runners who don’t need to or should not be looking to lose body weight, it’s important to focus on the other benefits of eating a higher protein diet like building muscle. And always remember that weight loss is certainly not a given if you simply toss a bunch more protein into your diet.

The Downsides of a High-Protein Diet

High-protein diets are not without some risks for athletes:

1. Fewer Carbs
Increasing your intake of protein means that overall calorie intake must increase or consumption of either carbohydrates or fat must decrease. In many cases, high-protein diets restrict carb-rich foods, like grains and potatoes, to varying degrees. “And eating lots more protein may leave an athlete feeling too full to consume adequate amounts of carbohydrates,” Van Horn adds. That means a high-protein diet could crowd out carbohydrates, which can have a detrimental impact on both health and performance, particularly for runners.

Over the years, numerous studies have demonstrated that skimping too much on carbs can negatively impact various performance metrics in active people, including power output. And you would be hard-pressed to find any research showing that reducing carbs can be helpful to PB pursuits. “Too much protein and too little carbs can lead to lower glycogen stores that will result in insufficient energy available to adequately support exercise,” Van Horn says.

A 2022 study in Medicine and Science in Sports and Exercise involving elite male endurance athletes discovered that the negative effects of training on athletes’ iron levels and immune system were more pronounced when they consumed insufficient carbs, compared to when they ate a diet with insufficient calories but higher amounts of carbs. Some of the most common symptoms of low energy availability (a marker of RED-S) in athletes are driven by low carbohydrate intake, rather than just a low caloric intake overall.

2. Poor Gut Health
Here’s another reason why you may not want to go huge on protein at the expense of carbs: It could alter the make-up of the gut microbiome and this may be one of the mechanisms why low-carb eating can hinder endurance performance.

In a randomised control trial published in the journal mSystems, researchers assigned well-trained runners with similar dietary and physical activity habits to one of two highly controlled calorie-matched diets: higher protein (40 per cent protein, 30 per cent carbohydrate, and 30 per cent fat) or higher carb (10 per cent protein, 60 per cent carbohydrate, and 30 per cent fat), while measuring any changes in gut microorganism composition.

Perhaps somewhat predictable, the short-term higher carb diet resulted in greater performance on the endurance tests than did the lower carb, higher protein diet — eating more carbs improved time-trial performance by 6.5 per cent, whereas going bigger on protein led to a reduction in performance by about 23 per cent. The drop in performance on the lower-carb diet was accompanied by a significantly reduced diversity and altered composition of the gut microbiome among the study participants.

Researchers also found that the greatest athletic performance during dietary modification in participants with more gut microbial stability and less substantial shifts in community composition. In other words, going too low on carbs in favour of protein may stress the microbiome of calorie-burning endurance athletes and this potentially may contribute to drops in performance.

3. Health Complications
There is potential for some health repercussions if a significant amount of the protein comes from meat, especially red meat and cured meats. For example, higher intakes of red meats have been linked to an increased risk of death from cardiovascular disease, which may, in part, be explained by unfavourable changes in cholesterol numbers.

There appears to be less worry if people source more of their protein from other animal sources including fish, lean poultry, and yoghurt, instead of fatty cuts of steak, deli meat, sausage, and bacon. “I think we can all agree that too much of anything can warrant health risks,” says Van Horn.

Contrary to popular belief, research has found that higher protein intake doesn’t cause kidney problems in people with normal kidney function. However, clinical evidence does suggest that people with poor kidney functioning should not eat a high-protein diet.

4. Low Fibre
If one is not careful, a high-protein diet that is heavy in animal-based foods can come up short in fibre, which can cause constipation and other health concerns. But this is easily remedied by including enough higher-fibre foods like legumes, vegetables, and whole grains in a higher protein eating plan. For example, you can serve a big piece of chicken for dinner alongside some quinoa and steamed broccoli — a plate that will deliver both high amounts of protein and fibre. You certainly can still eat plenty of protein while also nailing your fibre needs, which is at least 14 grams per 1,000 calories of food you eat.

5. Higher Cost
You should also consider the cost of a protein-rich diet, more so if much of that protein in your diet hails from animals. Animal-based proteins like steak, Greek yoghurt, and fish are some of the most expensive purchases from the grocery store. And if you are using protein powders to get numbers up that won’t be cheap, either. This means a protein-rich diet can hit your food budget hard.

To keep expenses down, Van Horn recommends making sure to get some of your protein from less expensive sources like tofu, eggs, and beans.

So, Should You Follow a High Protein Diet?
Given the pros and cons, overall many runners should strive to consume a moderately high-protein diet to support training. But there is little evidence for the need to take it to extreme levels where you are getting 40 per cent or more of your calories from protein.

While the recommended dietary allowance for protein in the general population is 0.8 grams per kilogram of body weight daily, Van Horn stresses that athletes should consume more — at least 1.6 grams per kilogram of body weight. That means about 116 grams of protein for a 160-pound athlete. Most people would consider this amount a fairly high protein diet, most likely offering up at least 20 per cent of calories coming from protein, and also an amount is shown in research to bring on favourable muscular adaptations to training.

This is also a quantity of protein that Van Horn says should allow sufficient calories to also come from carbohydrates and fat. Remember, the higher your training load the more calories you should get from all of these macronutrients. Add a bunch of resistance training to your running and you may benefit from getting up to 2 grams of protein per kilogram of body weight.

The bottom line: There is no magic number here and it’s super individualised. Ideally, it helps to work with a sports dietitian so you can understand where your macro numbers should land, based on your age, weight, gender, level of activity, muscle mass, and general energy expenditure.

Easy Ways to Eat More Protein
Track your eating for a few days and see where you land in terms of protein intake. You might be surprised that you’re not hitting your protein goal. If you struggle to take in enough of the macro, here are some sneaky ways to work more into your diet:

• Make creamy dressings with Greek yoghurt
• Stir a scoop of protein powder into oatmeal
• At meals, serve an extra ounce of meat, like chicken breast
• Toss edamame onto salads
• Sprinkle hemp seeds on yoghurt and cereal
• Use hummus as a sandwich spread
• Include a hard-boiled egg with breakfast
• Blend cottage cheese into post-run smoothies

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