Protein intake, and should it change during a caloric deficit?

Protein intake and should it change during a caloric deficit?

How much protein should you be consuming during a calorie deficit? Here we are going to have a look at the facts, myths and general guidelines around the subject, so we can informed decisions on what is right for us regarding our goals.

Nutrition Qualification for Personal Trainers

What are the guidelines for protein levels?

The current guidelines for protein intake (in grams of protein per kg of bodyweight) are as follows:

Protein GuidelinesProtein Levels Needed
Sedentary adult0.8g/kg
Recreational adult exerciser0.8-1.5g/kg
Adult endurance athlete1.2-1.6g/kg
Growing teenage athlete1.5-2g/kg
Adult building muscle mass:1.7g-2g/kg

These guidelines start with the most basic nutritional requirement for an adult, otherwise known as your RDA (recommended daily allowance). The exact levels of protein grams per kilogram of bodyweight will vary from individual to individual depending on a number of factors, including activity levels.

Nevertheless, for a sedentary adult: 0.8g/kg is the minimum factor you should incorporate into your diet.

Clearly Define your goals to determine your protein intake.

Like all aspects of nutrition and training, it needs to be specific and individual to you and your goals. If you are something who is an endurance athlete, then your protein requirements are going to be different from someone who is looking to build lean muscle tissue.

Likewise, if you are someone who is looking to be healthier and exercises infrequently, your protein requirement is going to very different from someone who is trying to change their body composition.

Can you eat ‘too much’ protein?

A common misconception is that too much protein can be damaging to kidney function. This has never been proven in any major studies.

However, a 2018 study on the effects of a high protein diet vs a lower/normal protein diet found that higher protein diet does not adversely affect kidney function in healthy adults.

It should be noted, however, this study was done on healthy adults with no kidney dysfunction. If you, or your client, suffers from kidney issues (or liver issues), then a lower protein diet would be recommended (seek advice from a medical professional).

Should protein intake change when you switch from a caloric maintenance or surplus into a caloric deficit?

The first question you need to ask yourself is how much of a calorie restriction you are going to enter in to. Calorie restriction is typically defined a reduction in calories totalling 20-50% below habitual levels (normal consumption or caloric maintenance).

The more severe the caloric deficit, the more heightened the physiological effects will be and the more difficult it will be to sustain in the long term. For those reasons, a calorie deficit of 20% is typically recommended. (The reason these recommendations are in % is so that it is individual to each person’s currently dietary intake.)

When you enter into a caloric deficit, studies have shown that your bodies metabolic rate (Basal Metabolic Rate) will reduce, thus reducing energy expenditure. Furthermore, as your BMR is calculated using your current weight as one of the key multipliers, are you progress through your calorie deficit and begin to lose weight, then your BMR will reduce too.

Effectively your BMR figures is the number of calories you burn at rest for normal bodily function, therefore this number will decrease as your mass decreases, your total weight as an entity.

This means over time, your degree of weight loss may plateau, with higher decreases in weight at the start of your journey.

A 2018 study showed that weight loss through a 20% caloric restriction leads to a decrease in lean muscle tissue. Losing some muscle mass during a cut is inevitable, but how can we minimise the risk of this and maintain as much of the muscle mass we’ve built and keep our metabolism firing as high as possible?

protein intake in a calorie deficit

This leads us to our final question:

Should we increase protein intake during a cutting phase?

As we saw above, a calorie deficit can result in a decrease in muscle mass and a decrease in energy expended. One of the proven ways to increase or maintain your metabolism, is to increase or maintain your lean muscle mass.

A study on female physique competitors compared a high protein diet (2.5g/kg) vs a lower protein diet (0.9g/kg), both in a calorie deficit, over an 8 week period. The results showed the higher protein group gained more muscle mass and lost more body fat than their lower protein group, which indicates eating a higher protein diet can enhance lean mass during a deficit and promote simultaneous fat loss.

In conclusion, we can say that increasing our protein intake during a cutting phase will help to maintain metabolic rate, maintain or increase muscle mass and help to reduce total fat loss.

So how much protein should we eat during a caloric deficit?

Looking back at the guidelines and at new research and what they have shown, optimal protein intake during caloric restriction may fall around 2-2.5g/kg, depending on the individual.

Sources of Protein

Beyond the measure of how much protein one should consume in a calorie deficit (or in a surplus), its also important for the individual to carefully consider the broader picture and the micro nutritional benefits of the protein choices.

All proteins are made of amino acids, there are 20 amino acids that make up protein, 11 of which your body can make on its own however 9 of the amino acids must be retrieved from diet.

10 Food Sources of Protein
Lean Meat
Greek Yogurt
Milk / Dairy


Interested in learning more about nutrition and diet?

Take a look at our personal training courses and our nutrition for sport and exercise course. With our years of experience and a rock-solid 100% money-back guarantee, we have helped thousands of students gain the skills and the confidence to make their fitness careers successful.


1.2018 Nov 1. doi: 10.1093/jn/nxy197 Changes in Kidney Function Do Not Differ between Healthy Adults Consuming Higher- Compared with Lower- or Normal-Protein Diets: A Systematic Review and Meta-Analysis Michaela C Devries,1 Arjun Sithamparapillai,2 K Scott Brimble,3 Laura Banfield,4 Robert W Morton,2 and Stuart M Phillips2

2.1988 Oct;37(10):930-6. doi: 10.1016/0026-0495(88)90149-7. Weight Loss Leads to a Marked Decrease in Nonresting Energy Expenditure in Ambulatory Human Subjects D S Weigle 1, K J Sande, P H Iverius, E R Monsen, J D Brunzell

3. Med Sci Sports Exerc. 2017 Jan; 49(1): 206–217. doi: 10.1249/MSS.0000000000001074 Effects of Weight Loss on Lean Mass, Strength, Bone, and Aerobic Capacity Edward P. Weiss,1,2 Richard C. Jordan,1 Ethel M. Frese,3 Stewart G. Albert,4 and Dennis T. Villareal2,5

4. 2013 Apr 1. doi: 10.4161/adip.22500 Increasing muscle mass to improve metabolism Alexandra C. McPherron, 1 ,* Tingqing Guo, 1 , † Nichole D. Bond, 1 , ‡ and Oksana Gavrilova 2

5.Int J Sport Nutr Exerc Metab. 2018 Nov 1;28(6):580-585. doi: 10.1123/ijsnem.2017-0389. Epub 2018 Jul 3.

6.Effects of High Versus Low Protein Intake on Body Composition and Maximal Strength in Aspiring Female Physique Athletes Engaging in an 8-Week Resistance Training Program

7.Bill I Campbell 1, Danielle Aguilar 1, Laurin Conlin 1, Andres Vargas 1, Brad Jon Schoenfeld 2, Amey Corson 1, Chris Gai 1, Shiva Best 1, Elfego Galvan 3, Kaylee Couvillion 1

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