What role does protein play in weight loss?

When it comes to weight loss, protein is often treated like the magic bullet. On social media, in supermarkets or from the trendiest influencer you will see protein being thrown about as the key to losing weight. But is protein really the key ingredient for weight loss or just a popular trend? In this blog you’re going to delve into what protein is and the roles it plays in weight loss.

Protein powder being added to plastic shaker

What is protein?

Protein is one of the main macronutrients - along with carbohydrates and fats - that our bodies need to function properly. It plays a role in almost every biological process and is important for growth, repair and maintaining the structure of our body. Protein is made up of long chains of smaller units called amino acids, which are the building blocks of protein. There are 20 amino acids, 9 are essential which means our body cannot produce them on their own. So we must get them from food. This is easy to do - eating regular protein will ensure good intakes of these amino acids.

Protein and satiety in women’s weight loss

Research has found that protein is the most satiating macronutrient, this is because protein takes longer to digest, meaning you feel fuller for longer (1). For women, managing hunger is important as hormonal fluctuations throughout the menstrual cycle can make appetite and cravings harder to control. During the luteal phase (day 15-28 – based on the “average” menstrual cycle), women experience the biggest hormonal shift, from a rise in progesterone, which can increase appetite and cravings. Protein rich foods can keep you fuller for longer and reduce the likelihood of additional snacking and cravings that might influence your weight loss progress (2). A study found that compared to high-fat snacks such as cheese, eating less calorie dense, high-protein snacks, like yoghurt, improves appetite control and satiety, and reduces overall food and calorie intake in women (3). This is important for weight loss. Being hungry regularly can lead to overeating, which may not benefit weight loss if this leads to eating outside a calorie deficit. A calorie deficit is when you’re eating less calories than you are burning. The key is to feel full whilst eating less calories.

Preserving muscle in weight loss

When starting a weight loss journey the main goal is often to reduce body fat, but it's very common for people to overlook the risk for muscle loss during the process. A poor protein intake reduces muscle and this can have an impact on strength and physical function. This may lead to your body entering a catabolic state, where you're losing both fat and muscle. As we age, it is vital to maintain muscle and strength as this can have an impact on daily life such as carrying shopping bags or climbing stairs. The more muscle we keep the higher our metabolism stays as we age. Our muscle and strength peaks at around 30-35 years of age and after that our muscle power and strength slowly declines (4). This is especially during menopause, with the natural decline of oestrogen, where muscle mass, bone density and strength are lost (5). Making sure you consume enough protein during weight loss, aging and menopause can help maintain muscle mass and overall strength.

Metabolism and protein

Metabolism is the process of when the body changes food and drink to energy. Calories in food and drinks mix with oxygen to make the energy the body needs.

Women have a slower metabolism than men, meaning it can be harder to lose weight. However, protein gives a metabolism boost which is known as the thermic effect of food, which is the amount of energy needed to digest and break down food. Protein is ranked highest and uses 20-30% of energy therefore, protein-rich foods require more energy to digest and absorb, leading to a higher metabolic rate and improved energy levels (6). This means that you can naturally use protein’s thermic effect to naturally increase your metabolism to support gradual and sustainable weight loss.

What is the right amount of protein for me?

In the UK, on average we are eating more protein than required. It’s recommended that 0.75g protein per kilogram of bodyweight is consumed, which is roughly 45g/day for a woman weighing 60kg (7). However, women are approximately eating 67g/day - nearly 1.5 times the recommendation (7) for a 60kg woman. It’s likely the majority of us are already getting enough protein (7). Women who aim for weight loss should try to have ¼ of their plates containing a protein source, optimising satiety and being fuller for longer.

When exercising, a common question is - should I be eating more protein? The answer is you are most likely already eating enough! Unless you are a professional athlete with goals, many people who are sedentary or lightly active do not need to worry about protein intakes. A healthy balanced diet with a variety of food will help you meet your protein requirements.

If you’re concerned about your protein intakes, or believe you may need a higher intake, speak with a Registered Nutritionist (ANutr/RNutr) or Registered Dietitian.

Where can I find protein?

Below are some high protein food sources – aim to have ¼ of your plates being made up from protein.

Animal-based options:

Chicken breast
Turkey
Fish- salmon, tuna, cod and trout
Lean beef
Dairy - Cottage cheese, yoghurt, milk

Plant-based options

Lentils
Chickpeas
Tofu
Tempeh
Meat alternatives (e.g. quorn)
Quinoa
Nuts and seeds

Overall, protein plays an important role in weight loss. It helps boost your metabolism, preserves muscle and improves satiety. For women during the menstrual cycle, protein can help curb cravings that may lead to overeating. Consuming protein rich foods as part of a weight loss journey will help keep you fuller for longer and lead to long-term sustainable weight loss.

This blog is written by Amber Brown- a Bournemouth University student currently studying a MSc in Nutrition and Behaviour