Metabolism 101: Introduction to Metabolism and Nutrition

Metabolism 101: Introduction to Metabolism and Nutrition

Metabolism 101: Introduction to Metabolism and Nutrition

By: Maude Morin, Registered Dietitian, BSN, MAN, Reviewed & Edited by JM Nutrition Team


In this post:

  • Metabolism 101: The basics

  • What is metabolism?

  • How to speed up metabolism

  • How to slow down metabolism

  • Nutritional interventions 

  • Lifestyle factors that affect metabolism


In the post Metabolism 101, JM Nutrition’s registered dietitian, Maude Morin, examines the basics of metabolism, as well as the connection between metabolism and nutrition. 


Metabolism 101: The Basics of Metabolism

Before we examine the connection between metabolism and nutrition, let’s first take a brief look at what is metabolism.

What is metabolism?

Metabolism is all the processes involved at the cellular level in the making of and using energy. Learn more about the specifics of metabolism


Thyroid health and metabolic function

The role of the thyroid gland:

  • Regulates metabolism
  • Produces thyroid hormones T3 and T4
  • These regulate body temperature, energy use and overall organ function
  • By extension, weight is affected 

Related: Thyroid health support

Dietitian for hormonal balancing

Where does this energy come from?

Naturally, the energy comes from food. Consequently, the connection between food or nutrition and metabolism is fundamental.

The energy we consume is used to fill these four buckets:

1. Basal Metabolic Rate (BMR)

2. Thermic Effect of Food (TEF)

3. Non-Exercise Activity Thermogenesis (NEAT)

4. Exercise

Let’s analyze each of these in some detail.


Metabolic Rate

We simply cannot omit the topic of the metabolic rate in a metabolism 101 post. After all, it’s the centrepiece of the discussion and forms an important part of the basics of metabolism. 

What is metabolic rate?

Your basal metabolic rate (BMR) is the amount of energy or calories the body uses when you are at rest for essential life-sustaining functions. It accounts for 60-70% of your energy use. 

Factors that affect the BMR

There are a number of factors that affect the metabolic rate. These include:

  • age
  • genetics
  • lean mass
  • body size
  • sleep
  • gender
  • hormonal health (thyroid dysfunction: hypothyroidism)
  • temperature (environmental)
  • illness
  • infection
  • nutritional deficiencies
  • diet quality

Affecting change on the BMR

A common myth that circulates is that we cannot affect change on our metabolism. This could not be farther from the truth. Of course, there are factors such as genetics, age and body size that we cannot control. That said, however, it is no doubt possible to affect change on the basal metabolic rate via physical exercise and diet. Here’s how:

  • A balanced diet rich in plants and whole foods decreases deficiency
  • Dieting
  • Fasting
  • Consuming excess calories

How dieting slows metabolism

Simply put, when you lose weight, the BMR slows down. This is entirely normal–you’re in a small body after all!

When you lose weight, you also usually, though not exclusively, lose muscle mass. As a result, you lower the BMR. 

It seems that BMR slows more than is anticipated in people following crash or fad diets that lead to rapid weight loss.

Interestingly, slow and gradual weight loss does not seem to have the same effect on your metabolism. This is what makes slow and gradual weight loss something that can be maintained after it’s undertaken. 

Learn more: Exercise, metabolism and weight: New research from The Biggest Loser

Related: Dietitian support for weight loss

Myth: Yo-yo dieting means you have a broken metabolism.

Your metabolism can be broken or ‘sleeping’. There are, however, steps you can take to rectify this.

  • Ensure you eat enough food overall
  • Swap refined foods for minimally processed foods
  • Include muscle-building activity
  • Engage in physical exercise daily (e.g., walk) 

Protocol to follow: Ditch the diet

Why is that?

  • Under eating calories slows down metabolism. It may also result in muscle loss and poor immunity.
  • Overall low energy intake commonly creates nutritional deficiencies.
  • Dieting often leads to an unhealthy relationship with food.

Instead, build a whole foods diet, rich in plants, that’s sustainable for you.


Thermic Effect of Food

Before we tackle dietary changes to affect metabolism, let’s take a brief look at TEF, otherwise known as the Thermic Effect of Food.

What is thermic effect of food?

The amount of energy or calories burned to turn food into energy.

  • Digest
  • Absorb
  • Turn into energy in the cells (metabolize)
  • Store (often as fat)

This accounts for approximately 10% of the energy you use each day.

Which macronutrient has the highest TEF (burns the most energy)? 

Protein has the highest TEF.

TEF protein: 4 calories per gram of protein; 20-30% of these calories are used in metabolism.

TEF carbs: 4 calories per gram; 5-10% of these calories are used in metabolism.

TEF fats: 9 calories per gram; 0-3% of these calories are used in metabolism.

Protocol to follow: Meet your protein needs

  • Eat lean protein with most meals and snacks.
  • Make 25% of your main meals a source of protein.
  • Know your targets: 0.8g of protein per kg of body weight (to prevent deficiencies in amino acids).
    • Example: 190 lb. man = 69g/day
    • Example: 135 lb. woman = 49g/day

The current dietary guidelines recommend 0.36g per pound.

It’s also important to note that to achieve metabolic health, it can help to increase the above amounts, so that protein intake is higher depending on your age, health status and body/fitness goals. This will vary for muscle building, fat loss and endurance performance.

For more information consult our sports nutrition dietitians.


Non-Exercise Activity Thermogenesis (NEAT)

What is non-exercise activity thermogenesis (NEAT)?

Simply put, NEAT is the energy used doing just about everything. There are, however, three exceptions:

  • Sleeping
  • Eating
  • Sports-like exercise and working out

It accounts for 15-30% of daily energy use.

It’s also important to note that there is a good deal of room to improve the metabolic rate with NEAT simply by reducing sedentary behaviour. 

NEAT examples

  • Walking to work or to the store
  • Typing
  • Yard work
  • Taking a shower
  • Housework
  • Fidgeting

That said, we must remind that these activities do not replace the physical health benefits of actual cardio- and strength-based exercise.

What do we mean by exercise? 



When we refer to exercise, we refer to the energy used during moderate to vigorous intensity activity. 


  • Jogging
  • Cycling
  • Pilates
  • Resistance training

It accounts for approximately 5% of daily energy use. High-level or professional athletes are a notable exception. An even greater percentage of their energy use can come from exercise.

Current recommendations for exercise

The current recommendations for exercise call for 150 minutes of moderate to vigorous intensity activity per week & minimum of two resistance based workouts per week.

Related: Personal trainer and dietitian


Metabolism 101: Is There an Ideal Diet for Faster Metabolism?

This is a commonly asked question, one that we cannot omit, when analyzing metabolism basics.

Let’s take a closer look.

What is metabolic flexibility?

Metabolic flexibility refers to the body’s ability to use different forms of fuel for energy, depending on the nutritional choices you make.

In response to:

  • Meal composition
  • Periodic fasting (e.g. sleep)
  • Physical activity
  • Environmental factors

On a day-to-day basis, your metabolic rate shifts slightly, perhaps marginally, if at all. In fact, it’s quite consistent. Your body’s goal is to maintain homeostasis after all (or a state of consistency and stability).

Producing energy in the mitochondria needs glucose, no matter what. Having metabolic flexibility means we can make it from carbohydrates, or fats. For example, Keto vs. usual diet.

Related: Pros and Cons of Keto


Metabolism 101: Nutrition and Its Impact on Metabolism

Nutrition and metabolism are no doubt interlinked. 

Myth: “Metabolism diets” work the best to increase metabolism.

In actuality, the most effective way to speed up your metabolism is to add exercise and muscle-building activities to your routine.

Related: Nutritionist For Strength Training 

Let’s take a deeper dive into some of these “metabolism diets”.


Metabolic Typing Diet

  • Created in the 1960s.
  • Based on taking a quiz to determine the “metabolic type” or your BMR.
  • Rules:
    • Eat 5 small meals per day, no more than 4 hours apart.
    • Eliminate all refined carbohydrates.
    • Eliminate dairy, caffeine, alcohol and soy.

In a nutshell, the evidence of this diet’s effectiveness was and remains inconclusive.


Zone Diet

  • Created in 1995.
  • Goal: To reduce inflammation. Based on macronutrient proportions.
  • Based on macronutrient proportions:
    • 40% carbohydrates
    • 30% protein
    • 30% fat

On this diet there is no calorie restriction required. Simply apply the ratios to your best diet. This is a much more flexible approach overall. 


Atkins Diet

  • Created in 1972.
  • Similar to the modern keto diet.
  • Rules:
    • Macronutrient tracking.
    • Carbohydrate counting.
    • Very low carb: 20g-50g per day. Carbs comprise 10-15% on the Atkins diet, while a typical balanced diet calls for carb intake of 40-60%.

It is worth noting that low carb diets such as this one are not necessarily most effective for weight loss.


Metabolism 101: Important Nutrients for Metabolic Health

No discussion of metabolism basics is complete without an examination of the important nutrients that affect metabolic health. These include:

Vitamin D

Vitamin D Food Sources

  • Sardines
  • Tuna
  • Cod liver oil
  • Salmon
  • Dairy milks
  • Plant-based milks fortified with Vitamin D

Learn more about Vitamin D food sources.



  • Makes vitamin D function possible.
  • Deficiency is common in metabolic syndrome.
  • Reduces inflammation.

Magnesium Food Sources

  • Dark chocolate
  • Avocados
  • Legumes
  • Tofu
  • Nuts & seeds
  • Leafy greens
  • Bananas

Learn more about food sources of magnesium.



  • Body absorbs glucose.
  • Reduces insulin resistance.
  • Improves thyroid function.

Food sources of selenium

  • Brazil nuts
  • Halibut
  • Sardines
  • Turkey
  • Shrimp
  • Chicken
  • Brown rice
  • Bread

Learn more about food sources of selenium.



  • Makes vitamin D function possible.
  • Used to make insulin.
  • Helps to make thyroid hormones.

Food sources of zinc

  • Oysters
  • Beef
  • Crab
  • Pork
  • Legumes
  • Oats
  • Cashews

Learn more about food sources of zinc.


B Vitamins

Food sources of B vitamins

  • Salmon Eggs
  • Milk
  • Beef
  • Leafy greens
  • Legumes
  • Yogurt
  • Chicken & turkey

Learn more about food sources of B vitamins.



  • Reduces oxidative stress.
  • Excess intake causes liver damage.
  • Its deficiency is very rare.

Food sources of manganese

  • Whole grains
  • Clams
  • Oysters
  • Nuts
  • Soybeans
  • Legumes
  • Leafy vegetables
  • Coffee
  • Tea 

Learn more about food sources of manganese.


Metabolism 101: Nutrition and Metabolism 

Does when you eat affect your metabolism?

Let’s take a look.

Skipping breakfast

  • No known evidence to support this slows your metabolism. 
  • May affect how much you eat later in the day.
  • Total energy eaten per day is more important.

Eating late in the evening or late at night

  • Only problematic if most of consumed calories are eaten late.
  • Going to sleep hungry reduces sleep quality.

Protocol to follow: Eat most of your food-energy in your first few meals

  • Emerging research around “chrononutrition”.
  • This doesn’t mean you have to eat breakfast.
  • This doesn’t mean you cannot have a snack before going to sleep. Choose higher protein snacks at this time.

Examples of high-protein bedtime snacks:

  • Nuts
  • Boiled eggs
  • Yogurt
  • Edamame
  • Celery sticks with peanut butter 


Metabolism 101: Hydration and Metabolism 

Water is also no important when it comes to metabolism basics. 

  • Water intake can stimulate energy use.
  • Drinking water increases thermogenesis. Heat production; warming liquids to body temperature. 

Related: How much water should I drink?

Hydrating Foods For The Summer


Metabolism 101: Sleep and Metabolism

Sleep time and quality is a determining factor in your BMR. As such, it plays an integral role in metabolism basics. 

Sleep, Metabolism and Your Weight 

Poor sleep length or quality can lead to:

Learn more about sleep and weight loss

Protocol to follow: Get 7-9 hours of sleep each and every night

Sleep is the best:

  • Hormone regulator
  • Stress reducer
  • Emotional stabilizer

Undoubtedly, getting enough sleep on a regular basis is one of the main ways we have to refill our energy battery. As a result, the importance of sleep cannot be overlooked.

Related: Nutrition Tips to Help You Sleep Better

Nutritional support for sleep


Metabolism 101: Heat Exposure

Much like metabolism and nutrition are interconnected, heat exposure can also affect metabolism and, as such, we feel compelled to reference it in a metabolism 101 post.

How does heat exposure affect metabolism? It’s quite simple, really.

As your body is working hard to cool you down, you use more energy. 

Heat exposure:

  • Is thought to increase use of glucose (more energy production).
  • Could improve insulin levels.
  • Could improve your body’s use of stored fatty acids.
  • Is not a sure-fire tool for weight reduction. Research has yet to outline a perfect protocol or frequency, duration, or timeline for outcomes related body weight.

How can you safely expose your body to heat?

Sauna and hot yoga are just two ways to receive heat exposure. Just be mindful that prolonged and/or excessive heat exposure can cause heat exhaustion or heat stroke.


Metabolism 101: Cold Exposure

Cold exposure, too, may impact metabolism.

Cold exposure:

  • Contributes to decreases in inflammation.
  • Is thought to speed up metabolism in obese test patients.
  • Causes metabolism to increase (short term) to produce more heat.
  • Is not a sure-fire tool for weight reduction. Research has yet to outline a perfect protocol or frequency, duration, or timeline for outcomes related body weight.

Interestingly, cold exposure is thought to make you more cold-tolerant over time as your body produces more heat-generating fat cells (brown fat).

How can you expose your body to the cold in a safe way? 

Cold shower or bath are just two ways of doing so. As always, exercise caution when doing so. 


Parting shot

It’s worth noting that your metabolism is the life sustaining activity within every living cell in your body. We cannot affect changes to most factors that control our metabolism. That said, however, you can focus on taking care of yourself in other ways, and your metabolic health will follow.

In other words, follow metabolism basics: eat a wholesome, nutritious diet, exercise regularly and get adequate sleep on a regular basis. 


Although metabolism and its connection to nutrition are a multi-faceted topic, we’ve provided an adequate metabolism 101 overview, or a crash course in metabolism basics. We certainly hope it helped to shed some light on the matter, enabling you to go from here. 

For a personalized nutrition coaching for metabolism and nutrition matters with an on-site or virtual dietitian, book a free consultation or contact us for an appointment


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Maude Morin is a Saint John dietitian. She is a dietitian for women’s health, hormonal support, dietary management of PCOS, digestive health and more. Maude has appeared in a variety of publications including Reader’s Digest, Best Health Magazine, Toronto Star, Globe and Mail and many more.

Watch: Dietitian Maude Morin on nutritional counselling.

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JM Nutrition is a nutritional counselling service by registered dietitians and nutritionists in Canada. Main service area: dietitians Ontario, main office: registered dietitian and nutritionist Toronto.

Author: Julie Mancuso

Julie Mancuso

Julie Mancuso is a graduate of the University of Toronto, founder and owner of JM Nutrition, a nutritional counselling service by registered dietitians and nutritionists. For 15+ years, JM Nutrition has helped thousands reach their health, wellness and nutrition goals. Julie and her team regularly lend their expertise to a variety of health publications such as Reader's Digest, Livestrong, Business Insider, Food Network, Today's Parent, MyFitnessPal, Toronto Star, Elle Magazine, Best Life, Weight Watchers and many more.