Science of Fat Loss: Metabolism and Energy Balance
Science of Fat Loss:
Metabolism and Energy Balance
Metabolism is an important part of nutrition, but it can cause a lot of confusion in the fitness industry as it is often used synonymously with other terms such as ‘basal metabolic rate’ and ‘energy balance’. This post will help you understand these important aspects of nutrition and help to simplify what practical steps you should take towards sustainable fat loss.
Metabolism
A human’s metabolism is a complicated process that refers to all the chemical reactions inside the body that turn the food we eat into usable energy. It involves balancing the build up (anabolism) and breakdown (catabolism) of body tissue and energy. This is an extremely complicated process that (while very interesting to me) may not be that useful or helpful to delve into in this introductory post. The energy that is being balanced in these processes however, is very important to understand.
All food contains energy. To measure how much energy is in the food we eat, we tend to use the measurement of ‘calories’ in the fitness industry. Kilojoules can also be used as a measurement as well.
Energy balance
Generally speaking, if we consume the same amount of energy as we are using, we will be in ‘energy balance’ and weight will generally be maintained. While it can be more complicated than that, this is a simple place to start understanding how weight loss or weight gain occurs. You can view energy balance like a see-saw.
You may have heard of the term “calorie deficit” before. This is simply when you are consuming less energy (calories) than your body is using - meaning you will generally lose weight as a result.
How your body uses energy
Roughly 15-30% of our daily energy expenditure goes towards physical activity like sport, walking and even doing household chores.
7-15% goes to diet-induced thermogenesis (DIT) which is the energy your body uses in order to digest, absorb and store the food we eat.
The majority of our daily energy expenditure, however, goes to our Basal metabolic rate (BMR).
Basal Metabolic Rate (BMR)
‘Basal metabolic rate’ (BMR) refers to the amount of energy you burn each day to merely keep you alive, whether asleep or awake. These are things like:
Breathing
Circulating blood
Maintaining body temperature (generating heat)
Producing new cells
Recycling old cells
Adjusting hormone levels
Brain and nerve function
BMR is an important term to understand as 55-75% of the calories we burn in a day go towards these things that happen in the background.
The terms metabolism and Basal metabolic rate (BMR) are often confused for one another and when a person says they want to increase their metabolism, what they usually mean is that they want to increase their BMR.
An increased BMR means that the body will burn more calories at rest (and during exercise as well) meaning less of the food that is eaten will be stored as fat. This is the reason that some people can eat a lot more without gaining extra weight.
The opposite can be said for someone who has a low BMR. People with lower BMR burn fewer calories at rest and during exercise and therefore when overeating, more calories will be stored. Later in this post, we’ll go over some advantages and disadvantages to both faster and slower metabolisms.
What affects your BMR?
An individual's BMR is affected by many factors like:
Age
Lean muscle
Body mass
Gender
Genetics
Growth
Exercise
Metabolic disorders such as Type I and II diabetes
Lean muscle and body mass are the greatest determinants of BMR as lean muscle requires more energy to function and exist. Larger body masses will usually come with having larger organs and fluid volumes to maintain.
People who are ‘athletic’ usually burn more calories at rest simply because of the increased BMR they have due to the greater amount of lean muscle on their bodies.
What affects how much lean muscle you have?
Age:
As we grow older the amount of lean muscle on our bodies tends to decrease which also means a decrease in BMR. In order to minimise a reduction in lean muscle mass, it is vital to maintain protein intake for muscle synthesis.
Gender:
BMR is also affected by gender:
On average, females tend to have lower BMRs due to an increased amount of fat stores in the breasts and hips and generally lower levels of muscle mass.
On average, males have higher BMRs due to the higher amount of muscle mass and overall size.
Exercise:
In both cases of gender and age, exercise (particularly resistance training) can be used to maintain and increase the amount of lean muscle the body has. The opposite is also true, as when a person loses weight, their BMR decreases as the energy that was once needed to maintain body mass is now no longer needed.
Is it better to have a fast or slow metabolism?
A lot of clients ask me whether it’s better to have a fast or slow metabolism and my answer is usually “neither” or “it depends!”.
There are people on both sides of the spectrum - some whose body’s use more energy and some whose body’s use less energy. Neither are necessarily ‘healthier’ or ‘better’ than the other as there are many contributing factors that lead to health and all need to be considered to get a bigger picture of one's wellness.
Fast metabolism
While there are good arguments that a faster metabolism is ‘better’ for fat loss (as having a faster metabolism means your body burns more energy) there are some disadvantages to that too. People with faster metabolisms can find it hard to be in a caloric deficit (particularly if the deficit is too great) as their increased demand for energy can often lead to them feeling incredibly hungry, resulting in overeating.
This can often lead to developing poor relationships with food and oneself as hunger levels increase and the guilt associated with overeating often comes in drastic waves. Some other signs of a fast metabolism include:
Weight loss
Anaemia
Fatigue
Elevated heart rate
Increased body temperature
Insatiable appetite
Slow metabolism
In contrast to those with fast metabolisms, those with slow metabolisms require less consumption of food to maintain or gain weight and burn fewer calories at rest and during physical activity. While this can be a disadvantage for fat loss (depending how you work other factors around it), an advantage to having a slow metabolism is that it may delay aging.
This could be due to the fact that with a faster metabolism, the body must work harder, putting it under more stress, notes obesity expert Dr. Joel Fuhrman. A study published in a 2010 edition of “The Journal of Clinical Endocrinology and Metabolism” found that low thyroid activity correlate with an increased life expectancy (thyroid hormones play a big role in regulating metabolism and energy expenditure).
However, people with metabolisms that are too slow may also experience low energy levels and tiredness.
Neither are better or worse
The reason neither are considered healthier or better is that there are advantages and disadvantages to both depending on how you manage other factors surrounding it. The takeaway message is that weight gain and weight loss are not entirely dependent on your metabolism and is more to do with a number of other more important factors such as lifestyle habits, exercise, relative caloric intake to usage (energy balance), and coping strategies for stress and mood.
General Guidance
In general, I would advise everyone no matter where they are in their weight loss journey to evaluate these four key areas of their lives:
Diet
Exercise
Sleep
Stress
Also to make small changes when building healthy habits in these key areas. Making too big a change when you're not ready for it can lead to an unstable mood, energy, stress, and motivation - typically leading to weight regain and developing a poor relationship with food.
Diet Tips:
Education around what a balanced diet looks like (not only on what’s “healthy vs unhealthy”. There are many resources out there that can help you, including:
Recognise that everyone’s weight loss journey is different and comparing yourself to other people’s is not healthy or helpful.
Avoid fad diets that cut out entire food groups or promise quick results as this can lead to poor relationships with food and progress.
Avoid cutting out entire meals to be in a caloric deficit. Instead practice portion control by adding a serving of vegetables and redistributing portion sizes over three meals to avoid overeating. E.g. Vegetables can be consumed in large quantities making you feel full but without consuming many calories.
Include snacks in your daily diet. This will help you to feel less hungry when it comes to meal times and decrease overeating during meals. It will also improve the stability of mood and energy throughout the day which can help with motivation and consistency.
Exercise Tips:
Exercise in a variety of ways that are to your level - it doesn’t “have to be” what you see others doing - e.g. not everyone likes running. It’s generally a good idea to try and find something you enjoy doing so that you don’t view it as a chore. Walking in nature is a great start!
Stress Tips:
Lots of people struggle with stress and a very common coping strategy for many is to eat. This is because the hormone cortisol is released which signals the body to increase the secretion of insulin. Higher levels of insulin then lead to low blood glucose which then leads to the body wanting more food for energy. Food also offers comfort, which can be over-used as a coping strategy for stress. Finding healthier coping strategies is important in helping you relieve stress.
Find something that can help you relieve stress when you recognise it building up. Things like the following are really good options for relieving stress:
Dancing and exercise
Reading
Drawing
Enjoying nature
Talking to friends and family
Listening to music
Sleep Tips:
Not getting enough sleep can also increase cortisol levels and negatively impact motivation and decision making. The recommended amount of sleep is 7-9 hours per day. Insufficient sleep can also destabilize energy levels and cause fluctuations in mood, leading to an increased chance of stress eating and a poor relationship with food.
Manage your stress levels (this can look different for everybody)
Consistency can be helpful - e.g. consistently wake up at the same time
Minimise screen time leading up to bed time
Exercise regularly during the day
Enjoy nature during the day
Quick Point On ‘FAD Diets’
“A fad diet is a diet that becomes popular for a short time, similar to fads in fashion, without being a standard dietary recommendation, and often making unreasonable claims for fast weight loss or health improvements.”
While there are some fad diets that you can healthily incorporate into a long term plan, they usually aren’t recommended by health professionals because of the unrealistic claims of fast weight loss that they tend to make. This mindset focused on quick results can be unhelpful as drastic changes can be detrimental to mid-long term success.
A lot of fad diets reduce the amount of calories that are being consumed at too drastic of a rate or cut out entire food groups, which can be unhelpful in the long run as this increases your chances of developing poor relationships with food. Losing weight too quickly can negatively impact your overall weight loss journey as by decreasing energy intake too drastically, your body responds by slowing down your basal metabolic rate (BMR) more than it normally would, meaning less energy is used throughout the day and more is likely stored.
For this reason, it is not unusual for people engaged in drastic dieting to experience rapid weight loss at the beginning and then plateau, even though they are still decreasing calories. This can be demoralising as it feels like all the hard work and dedication is having no impact and can lead to decrease in mood, energy, and overall health.
If you are wanting some guidance or help with fat loss or nutrition as a whole, please don’t hesitate to reach out!
Our qualified nutritionists are more than happy to help.
Authors: Ian Yang (ONI Nutritionist) and Laurent Pang
ONI Personal Training | Massage Therapy | Nutrition Coaching | Movement Coaching