Does Protein Make You Gain Weight?

Overview

Protein is an essential nutrient that supports various body functions, such as muscle growth, metabolism and immune function. It should constitute 10–35% of the energy source in our daily diet.¹ Excess protein can result in weight gain due to increased lean body mass. In less active people, excess protein may be stored as fats and increase fat mass. High-protein diets with low levels of carbohydrates and fibre may also promote weight gain due to craving, binge eating and high energy absorption, respectively.

Why Take Protein?

Role Of Protein

From structural support to interactions between cells, protein is a crucial nutrient the body needs to support various biological processes. 

Protein comprises of chains of amino acids linked together by peptide bonds. When we consume protein, it will be broken down into amino acids and absorbed through the enterocyte in the gut. At the cellular level, amino acids are used for cellular processes such as protein and DNA synthesis. At the organismal level, amino acids are used to produce proteins that carry out various functions in the body, such as enzymatic actions, chemical communication, muscle building and immune functions. 

There are 20 amino acids that are used by all living organisms. These amino acids can be further categorised as:

1. Nonessential amino acids and 
2. Essential amino acids

Nonessential amino acids can be produced in the body, whereas essential amino acids cannot be produced in the body and have to be acquired through diets. Contrary to what the names suggest, nonessential and essential amino acids are important and should be in their optimum ratio to maintain health. ² 

There are nine essential amino acids that our body obtains from our protein intakes: ²

• Phenylalanine
• Valine
• Tryptophan
• Threonine
• Isoleucine
• Methionine
• Histidine
• Leucine
• Lysine

Recommended Consumption 

According to the Recommended Dietary Allowance (RDA), the amount of protein that we need to consume each day is at least 0.8g per kg of body weight.¹ Depending on age, level of activity and health conditions, one might need more protein than the RDA recommended value. Older or more active people may require more protein in their diet, around 1.2g per kg of body weight, to repair muscles and maintain muscle strength. Infants and children also need higher protein content in their diets because they need protein for growth.¹ The maximum amount of protein a healthy adult with an average activity level should consume in a day is about 2g per kg of body weight.¹ 

Sources Of Protein 

Protein can be acquired through animal products such as:

• Eggs
• Milk
• Whey proteins
• Meat
• Poultry
• Seafood

Plants that are good sources of protein include:

• Legumes
• Cereals
• Quinoa
• Beans
• Nuts

Muscle Growth 

One of the main functions of protein is to fuel the synthesis of muscle proteins, which help in muscle growth. Our muscle proteins undergo degradation and synthesis. With sufficient intake of high-quality dietary protein, there are enough amino acids to produce muscle proteins and exceed muscle protein degradation, helping promote muscle growth. In a study conducted in 2020, the researchers found that lean body mass, which is the body mass after deducting fat mass, increases when protein intake increases. The researchers also observed that resistance training enhances muscle protein synthesis and increases muscle mass.³ 

Recovery 

Protein is especially important in post-exercise recovery. Exercises increase the rates of breakdown and synthesis of muscle proteins, also known as the turnover rate of muscle proteins. Sufficient protein from the diet balances out the loss of muscle proteins by stimulating the synthesis of muscle proteins and providing the amino acids for the synthesis.

Does Protein Make You Gain Weight?

How Could A High-Protein Diet Lead To Weight Gain?

You're Eating Too Much 

In a study conducted in 2012, the researchers tested whether overfeeding participants with low-, normal- or high-protein diets would cause weight gain. They found that overeating caused the most significant weight gain in participants given a high-protein diet.⁴ The high-protein diet participants gained more lean body mass compared to other participants. 

There were also suggestions that long-term high consumption of animal proteins, in particular, was associated with weight gain.⁵ Some high-protein foods, such as red meat, also have high-fat content; eating too much of them can lead to weight gain.  

You Aren’t Exercising Regularly

Protein in our diets is one of the main calorie sources. A calorie is an energy released from the food we consume when our body digests it. About 4 calories are released for every gram of protein broken down. Therefore, excess calorie intake from a high-protein diet can cause weight gain if the calories are not ‘burned away’.

When you have too much protein in your diet, it will be broken down into amino acids that are converted and stored as fats in the adipose tissues.⁶ These stored fats can supply energy when your body requires more energy than usual, for example, during exercise. If you have a sedentary lifestyle and do not exercise regularly, you are not utilising the stored energy in the form of fats. As a result, the energy you take in as calories outweighs the energy that you use, which causes weight gain in the long run. 

Low Carb Results In Binges

Restricting the intake of carbohydrates by increasing protein intake may lead to binge eating episodes and, subsequently, weight gain. It was suggested that low glucose levels in the blood activate the brain regions involved in reward and motivation, which results in a craving for high-calorie foods such as high-sugar or high-fat foods. Our body works this way to ensure that we have sufficient glucose to support metabolic processes, especially in the brain, where glucose is the primary energy source. It is recommended for healthy adults with normal activity levels to maintain the optimum intake ratio of each macronutrient: carbohydrates (45–65% of energy), protein (10–35%) and fat (20–35%).⁷

Low Fibre

Fibre comprises large carbohydrate molecules that cannot be digested and absorbed in the gut. We need fibre to support the metabolism of our gut bacteria. Gut bacteria produce metabolites such as short-chain fatty acids (SCFAs) that are important to maintain colon health, support anti-inflammatory functions and regulate the gut's pH level to ensure optimum nutrient absorption conditions.⁸ Besides that, fibre plays other roles in maintaining health:⁹

• Improves gut motility to prevent constipation
• Improves weight management by making you feel full quicker
• Reduces cholesterol and risk for heart diseases
• Improves blood sugar control by reducing the absorption of glucose

The recommended minimum daily requirement for fibre is 30g.¹⁰ High-protein diets include foods which contain little fibre, such as meats, dairy products, seafood and poultry. Fibre has been suggested to facilitate weight loss by reducing the absorption rate of nutrients to control the intake of energy.¹¹ Low fibre in diets may cause you to take in more food because you do not feel full as quickly.  

Fibre naturally occurs in plant-based foods. Some good sources of fibre and protein include:

• Beans
• Legumes 
• Cereals 
• Whole grains
• Vegetables 
• Fruits

How Does Protein Consumption Impact Hunger Hormones

Protein generally has a satiety effect, making you feel full and less inclined to continue eating. This is because protein inhibits the production of the ghrelin hormone, which is a hormone that stimulates your appetite and encourages food intake. In addition, protein elevates the concentration and sensitivity of the leptin hormone, which is a hormone that promotes satiety.¹² Sufficient protein intake can help in weight management by promoting satiety, whereas excessive protein intake may cause weight gain instead because of higher energy consumption. 

Other Side Effects Of Taking Too Much Protein

It was suggested that taking a high-protein diet for a prolonged period may lead to decreased insulin sensitivity.¹³ Insulin is a hormone that regulates our blood sugar level by stimulating the sugar uptake by body tissues, such as muscle tissue and adipose tissue. A low insulin sensitivity means that the tissues that originally respond to insulin stimulation to take up sugar become less responsive, leading to excess sugar in the blood, causing hyperglycaemia (high blood sugar levels). In the long run, hyperglycaemia can cause Type 2 diabetes. 

Besides, there have been suggestions that high protein consumption in the long term can lead to calcium loss and reduced bone strength. This is because protein amino acids release hydrogen ions when metabolised and lower the pH in the blood. Then calcium is released from the bone to neutralise the increased blood acidity. This can result in reduced bone mineralisation and reduced bone strength, which can increase the risk of bone fractures.¹⁴ 

Excessive protein intake, especially animal protein, promotes the formation of kidney stones. Animal protein contains high levels of purines which increase the production of uric acid. In acidic conditions, uric acid has reduced solubility and precipitates to form uric acid stones.¹⁵

When To Be Concerned You Are Taking Too Much Protein

It was suggested that our daily protein consumption should be kept between 0.8–2g per kg of body weight. Taking  protein excessively may cause the following symptoms:

• Constipation – due to lack of fibre
• Headache
• Bad breath
• Indigestion
• Burning sensation when urinating – due to low pH urine¹⁶

Summary

A high-protein diet combined with high food intake, little exercise, low carbohydrates and low fibre can result in weight gain. Excessive protein intake can also cause adverse effects such as reduced bone strength, formation of kidney stones and increased risk for diabetes. You should consume protein according to the recommended amount and exercise regularly to better manage your weight and maintain your health.