How does protein give you energy?

Egg, salmon and avocado on toast
(Image credit: Getty)

How does protein give you energy? If you've ever finished a tough workout and felt completely drained, like your muscles have turned to jelly and the steps leading to your front door look like Mount Everest, it's an important question to know the answer to. If this sounds like you, you may benefit from adding protein to your routine. Protein is wonderful fuel for the body and it can help you to repair muscle and feel your best after working out. 

Protein can thus be hugely beneficial, especially if you have a very active lifestyle. If you prefer to take a supplement, rather than relying on getting extra in your diet, check out our guide to the best protein powder (or the best vegan protein powder if you're plant-based), as well as the best protein bars to snack on-the-go.

So, how does protein give you energy? Protein doesn’t actually give us an immediate boost but it’s important in the long-term prevention of fatigue, helping the body to repair and build tissue. Read on to find out more.

Why do we need protein?

What is protein? Protein is what is known as a macronutrient. This means it's a nutrient that the body needs in large quantities for energy and as an essential part of any diet. It's most often found in animal products, but it can also be found in plentiful supply in plant-based sources such as nuts and legumes. 

We all know that the body requires food for energy. But you may not have realized that protein is responsible for a large portion of the body's energy supplies.

Protein can also help you feel full, so it's essential for regulating the appetite. As one 2014 Nutritional Journal study showed, eating protein rather than sugar leads to lower levels of hunger later in the day. 

It keeps the body functioning optimally, contributing to normal energy levels, a healthy appetite and even brain function.

Steak and chicken breast with garlic and herbs

(Image credit: Getty Images)

How does protein give you energy?

So, what exactly happens in the body when we consume protein, and how is it converted into energy? 

As Dr Benji Dhillon, Cosmetic Surgeon at Define Clinic and skincare expert at Innermost, explains, protein isn't actually the body's preferred method of directly generating energy. 

Usually, the body prefers to use carbohydrates for its energy supplies first and foremost, because they are easier to break down into glucose. After using any stored carbs in the body, the second preferred method of generating energy is through fats, which are harder to break down.

Only a small amount of protein is directly converted into energy, because it isn't stored away in the body like carbohydrates and fats. When the body has run out of carbohydrates and fats to convert into energy, it does start to use protein. However, because protein supports the muscle-makeup of the body, this usually means that the body starts to break down your physical muscles. 

a balanced plate

(Image credit: Getty Images)

While protein isn't the ideal source for energy, including it in your diet is crucial if you want to maintain high energy levels. By consuming both carbohydrates and protein, for instance, you'll maintain steady blood sugar levels, which means you'll be less likely to experience that energy crash mid-way through a workout. Protein also helps you maintain muscle mass, which in turn supports a healthy metabolism rate. 

Protein is also essential for storing iron in the body, which in turn helps to keep energy levels up.

"Protein is a long term energy source and good for endurance," Dhillon says. "However it also helps muscles to repair and build – the stronger our muscles, the more likely we are able to go harder and faster in exercise and life in general." 

So, while protein may not directly give us energy, it's a crucial part of any active lifestyle and without it, you may find your energy levels aren't as high as they could be.

How much protein should be integrated into a balanced diet?

According to Harvard Health, the Recommended Dietary Allowance (RDA) is 0.8 grams of protein per kilogram of body weight. However, if you lead a very active lifestyle, you may wish to increase your protein intake from the minimum recommended amount to ward off fatigue and support muscle growth. Try using the USDA DRI calculator to accurately determine your recommended nutrient intake based on your body type and lifestyle. 

We recommend speaking with your doctor or nutritionist if you're considering changing the amount of protein you include in your diet. While high protein diets are popular, they aren't always the best option for a balanced, healthy lifestyle.

Eating too much protein can come with some bad side effects, including: 

  • Weight gain. A 2016 study published in the journal Clinical Nutrition showed that too much protein can lead to weight gain and cardiovascular issues.
  • Digestive problems. Too much protein can result in cramps, constipation, diarrhoea, or bloating, according to an ISRN Nutrition study.
  • Kidney disease. One 2020 PubMed study found that excessive protein could lead to kidney hyperfiltration. 
  • Risk of cancer. A 2014 Cell Metabolism study showed that high-protein diets could be linked to a heightened risk of dying from cancer.

To sum up, while protein isn't the key nutrient the body needs for energy, without it you can easily become fatigued while working out. Plus, protein helps to support muscle growth and muscle repair. So, if you want to fend off fatigue and to feel your best during and after your workouts, including protein in your diet is essential. Just be careful to always eat protein in relative moderation and as part of a full and balanced diet. 

Meg Walters
Freelance Writer

Meg Walters is a freelance journalist and features writer. Raised in Canada and based in South East London, Meg covers culture, entertainment, lifestyle, and health. Her work has appeared in Cosmopolitan, i-D, Refinery29, Stylist, GQ, Shondaland, Healthline, HelloGiggles and other publications. When she's not writing, Meg is probably daydreaming about traveling the world, re-watching an old rom-com with a glass of wine, or wasting time on Twitter, where you can follow her @wordsbymeg.