Most people will understand the basic idea of metabolism being the factor that determines how much food can be consumed to not gain weight. But what really is metabolism, what makes up your metabolism and how is it affected? Metabolism is the process by which our bodies convert the food we eat into energy. It's essential to sustaining life. Metabolism is the body's rate of energy production. It is basically the speed at which food is converted into energy. This energy production happens through a process known as respiration. Respiration is the specific chemical reaction that releases energy from food, and thus supports all of our daily functions. Energy production can take place in several ways, but it mainly comes from the burning of fats (fatty acid oxidation) or carbohydrates (glycolysis), using oxygen to "burn" these substances. Every single day your body breaks down carbohydrates, protein and fat into small molecules so it can use them for energy. Our metabolism is made up of four factors; BMR Basal metabolic rate, NEAT (Non exercise activity thermogenesis), EAT (Exercise activity thermogenesis) & TEF (Thermic effect of food). This is what we refer to as TDEE, total daily energy expenditure.
Basal metabolic rate (BMR); BMR relates to the energy required to keep the body’s basic functions running. All parts of the body require energy including our vital organs, brain, muscle tissue & digestive system. This generally makes up the biggest portion of our daily energy requirements and is the most affected by age, gender, hormones and muscle tissue ratios changes etc.
Non exercise activity thermogenesis (NEAT): Neat comprises all the activity performed throughout that day that is not targeted exercise. This will be made up of everything you do that requires energy such as going to work, walking to the classroom, doing the dishes, making the bed, cooking dinner. Any activity that requires movement or energy is categorized as NEAT.
Exercise activity thermogenesis (EAT) This is your exercise, whether it be going for a run, doing a spin class, bootcamp, weight training session at the gym, yoga or whatever activity used to be specifically part of your exercise routine.
Thermic effect of food (TEF):
This is the energy required to digest macronutrients. Normally around 10% of our daily metabolism is made up of TEF. Depending on which foods are being consumed the number of calories utilized just in the digestion process can vary. Protein can utilize around 20-30% of the calories in the digestive process, carbs 5-10% and fats 0-3%. For example, each gram of protein contains 4 calories so if I have 25 grams of protein in a meal 100 calories comes from protein sources. If a 30% TEF is used only
70 calories are available for utilization or storage depending on if you’re in a calorie deficit or surplus. What this means that for a period after eating, the metabolism is spiked, and the more protein ingested has a higher level of increase to your metabolism. This is a main reason why when trying to lose body fat, increasing protein intake has metabolic benefits.
It's important to understand that our metabolisms are fluid and change from day to day. There are many factors that can affect it, such as sleep quality, hormone balance, protein intake, types of exercise and what we are doing during any given day. For example, if I go for a 5km run in the morning and then sit around and watch movies for the rest of the day my metabolic output wouldn’t be as high as compared to a working day in a physical job. Exercise is great to help improve caloric output, which can lead to better energy levels, body composition and weight management. However, if your goal is to lose body fat, focusing on proper nutrition and caloric intake will be best to help obtain your fat loss goals. The best strategy is to try and bring a combination of all factors, exercise regularly, eat nutrient rich whole foods, increase protein intake, increase your NEAT, and plenty of rest and sleep to aid recovery.