The Effect of Diet on Your Metabolism

Energy is key to sustaining life. Without it, even basic functions like breathing and pumping blood around the body are impossible. But what do we mean by metabolism?

Simply, it’s all the chemical processes going on inside your body that contribute to its normal function. But metabolism isn’t static. Your metabolic rate can change throughout life, and be affected by numerous factors, including age, sex, activity level, and diet.

Here, we’ll investigate the effect diet can have on your metabolism and how your eating habits could be messing with your basal metabolic rate (BMR). Plus, we’ll also bust some of those popular myths, like can cutting out carbs really boost your metabolism?

Everything your body does requires energy - even digesting food. If more energy is required than is being acquired from your diet, your body will burn fat and eventually muscle. If it’s getting more energy than it knows what to do with, the cells will start to store it, leading to weight gain. Hence there is a fine balance required, and your diet is key.

Macronutrients, specifically, carbohydrates, proteins, and fats, are the main components of food and serve as the main fuel sources for the human body. The breakdown and digestion of these nutrients enable cells to transform the potential chemical energy hidden within our food into something useful.¹

Let’s take a look at how each of these macronutrients power our metabolism.

Carbohydrates are sugars, starches, and fiber and include fruit, vegetables, dairy products, whole and even processed grains.

But carbs are not created equal and the digestion process can have a variety of effects on your metabolism.

1. Monosaccharides or simple sugars like glucose and fructose are quickly released into the bloodstream and used as energy by cells. You’ll burn fewer calories when digesting them. 

2. Starch is an example of a complex carbohydrate. The enzyme, amylase, is required to break starch down into smaller sugars like glucose,² an energy-reliant process.

The metabolism of carbohydrates is vital for supplying energy to your cells. It’s part of the reason why long-distance runners ‘carb up’ before a big race, to ensure they have enough energy to get to the finish line.³ But as we know some are easier to digest than others.

Proteins are chains of amino acids or the ‘building blocks of life.’ Proteins are found throughout the human body - in your skin, hair, muscles, and just about every tissue.

Most adults need approximately 0.8 - 1.5 grams of protein per kilo of body weight each day.⁴ We cannot store proteins, so they must be converted to sugar (glucose) or fat (triglycerides), so they can be used or stored as energy.

To digest and metabolize food, some calories must be used in the process, after all, everything we do requires some energy. The energy needed to digest food is called the thermic effect of food (TEF).

Compared to carbs and fat, protein digestion has a much higher thermic effect which may boost metabolism. Some research shows that a high-protein diet can increase both metabolism and calorie burn-off.⁵ In other words, digesting proteins means your body burns more energy because it is working harder, speeding up your metabolism.

Fat metabolism breaks down the fat present in food into fatty acids and glycerol which can be used to generate energy.⁶ The process relies on energy, speeding up your metabolism.

Yes, fat can boost your metabolism - but, of course, it depends on its quality and composition. Saturated fat, for example, is associated with higher rates of weight gain.⁷ So, choosing unsaturated fats instead is a healthier option and even helps reduce your risk of heart disease.

It’s not just macronutrients that have a critical role in metabolism, micronutrient vitamins and minerals do too.

• Vitamin C is essential for the production of energy and the transport of long-chain fatty acids into the mitochondria powerhouses of your cells.⁸

• All B vitamins, except folate, are critical to energy production. A deficiency in any one of these vitamins can have metabolic consequences and decrease energy production.⁸

• Iron is essential for many processes in the body, particularly growth and development, and the production of red blood cells. It’s also directly involved in energy metabolism, and, in excess or deficiency, iron can have a detrimental effect on your overall health and wellbeing.

• Magnesium has many vital roles in human health, including energy metabolism, and deficiency can result in diminished exercise performance.⁹

Your eating habits can be a metabolism booster but they can also have the opposite effect. Here are some things you can do to support yourself.

Avoid skipping meals 

We’re all guilty of skipping meals at times. Whether it’s because we got up late and don’t have time for breakfast or are meeting friends for a big dinner, so we skip lunch to compensate, missing out on these vital calories can cause our metabolisms to crash.

The simplest way to think about it is: just like a car without fuel can’t function, neither can our bodies. Without food and the energy it yields, our cells, tissues, and organs cannot function effectively.

So, always try to eat every meal - it will do your metabolism more good than harm!

Prioritize protein 

If you’re looking to lose weight or build muscle, increase your protein intake. Protein keeps you feeling fuller and boosts your metabolism.

Research shows that high-protein, low-fat diets have a higher energy cost which, in turn, is beneficial for weight loss.¹⁰ Protein-rich foods include: 

• Lean meat - beef, lamb, pork 

• Poultry - chicken, turkey, duck 

• Dairy - milk, yogurt, cheese 

• Fish and shellfish - prawns, crab, lobster 

• Eggs 

• Nuts and seeds 

• Soybeans

Be conscious and consider the amount of fat in these sources as well e.g. red salmon has 12 gram of fat as well as 22 gram of proteins per 100 gram. This further limits the foods in a high-protein, low-fat diet.

Stay hydrated 

Water is vital for all life. That should be a good enough excuse to drink plenty, but if you need a little more convincing, here goes. Water is essential for metabolizing stored fat into energy. It’s so important that even mild dehydration is enough to slow your metabolism.⁹ So, if you’re trying to lose weight, not drinking enough water can actually slow your progress.

Meal timing is everything 

Timing your meals is essential. Start your day with a hearty, energy-boosting breakfast like porridge, approximately one hour after you have woken up. Breakfast is the perfect way to deliver the vital energy your body needs to start the day. After all, the clue is in the name: break fast.

If your lifestyle doesn’t fit the usual 9 to 5, ensure you eat during active hours. This will allow your body to use up the energy you are consuming rather than store it. 

Because metabolism refers to the conversion of what we eat and drink into energy, there are many popular myths about how increasing our metabolism will cause weight loss. But it’s not always quite as simple as that.

Do metabolism-boosting foods exist? 

There is little evidence available to support the idea that there are specific foods that boost metabolism, but certain foods could impact your daily energy expenditure. It’s important to avoid habits like crash dieting or calorie counting if you want to lose weight because these are not long-term solutions. Besides, diet is just one aspect that contributes to your metabolic rate.

Cutting carbs will boost metabolism 

Some studies have suggested that low-carb diets increase your metabolism and ultimately help you to lose weight, but cutting out any food group can affect other areas of your health and well-being.

It’s important to know that not all carbohydrates are the same. Just as no two people are. So, your body may react differently to someone else’s if you cut carbs out of your diet. The important thing is to eat the right carbs.

Eating before bed slows your metabolism 

Nighttime eating has been a topic of conversation for years, with conflicting evidence about its pros and cons. However, some research shows that if the snack of choice is small, nutrient-dense, and low in energy, rather than a large meal, it may have positive physiological outcomes for healthy individuals.

In obese populations, when combined with exercise, negative consequences seem to be eliminated.¹¹ So, the key is to keep it small, and nutrient-rich, and make sure you’re getting plenty of exercise.

Overall, the key to a healthy metabolism is balance. Cutting out carbs, crash dieting, or fasting may all help you to lose weight in the short term, but they can wreak havoc on your metabolism and actually cause weight gain shortly after.

Be sure to follow a lifestyle that incorporates all of the food groups, eat at consistent times, and stay hydrated - all of these will help to boost your metabolism. Remember, what you eat is just one aspect of metabolism, other lifestyle factors such as exercise and sleep are also important.