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Our metabolism, or metabolic rate, is the rate at which our body expends energy. Metabolism refers to the myriad of chemical reactions that take place within the body to allow for normal function. It will determine how much energy we require for our bodies to function properly. Our Metabolism is what governs how much energy we burn every day, and therefore governs how much food we should consume. It is individual and therefore accurate testing is required to know just how your body works. It is effected by
- Body Size* - Larger bodies generally have more metabolising tissue
- Body Composition* - More lean muscle = faster metabolism
- Age – Metabolism slows with age due to a reduction in muscle, hormonal and neurological changes
- Gender – Males tend to have faster metabolism (due mainly to body size and muscle mass)
- Growth – Regeneration and childhood / adolescent growth will increase energy requirements
- Genetics –Predisposition to certain metabolic rate may be inherited
- Hormones & Nervous System – Metabolism controlled by these systems (medical intervention may be available)
- Dietary deficiencies* - Lack of certain vitamins and minerals may lead to poor metabolic function
- Crash Dieting / Starvation* - An extreme reduction in calories (food intake), skipping meals, or long periods between meals actually slows your metabolism in order to conserve energy.
- Frequency of eating* - Smaller, more frequent meals increases efficiency of metabolism
- Amount of physical activity* - Regular medium - high intensity exercise increases fitness and the body’s ability to burn calories.
* These factors are within your control, and therefore intervention can help you change your metabolism and aid in reaching your health and fitness goals.
Our Resting Metabolic Rate (RMR) governs 50 – 80% of our total energy expenditure. Therefore, it would make sense to know exactly what our RMR is. This will then govern the amount of calories we consume (food), and also allow us to focus training efforts on increasing metabolic rate and energy expenditure. That way, you will be burning more fat while you go about your daily business. Similarly, by tracking our metabolism over time, we can monitor changes and effectiveness of intervention. No need for “one size fits all” diets. Rather, personalised healthy eating plans can be developed to suit your body.
Other factors adding to your Total Energy Expenditure (TEE) include the energy used for physical activity. This includes getting around and performing daily duties and can obviously be increased by increasing the amount of incidental activity you do (eg. Taking the stairs as opposed to using the elevator), and by including exercise in your day. This may contribute approximately 20% of your energy use for the day.
The Thermic Effect of Food, the energy used to eat, digest and metabolise food, contributes 5 – 10% of total energy requirements. Eating smaller meals more frequently (5 – 6 daily meals/snacks) increases the input of the thermic effect of food on daily calorie requirements. Your body will actually slow its metabolism to conserve energy when meals are frequently skipped or crash dieting occurs due to the lack of nutrition entering your body. If your body doesn’t know when it’s going to get fed next it will conserve energy. Regular eating habits allow your body to maintain constant metabolic functions. Also, smaller meals are easier for your digestive system to handle and process for nutrients rather than an abundance of food all at the one time.
When you really think about diets and eating plans that promote a 90kg man and a 60kg woman to eat the same foods, and the same amounts of food, they make no sense at all. If that eating plan was at the right levels for the 60kg woman, the 90kg would be being grossly underfed, which as aforementioned may be working against our metabolism goals.
Energy Balance refers to the relationship between our Energy Intake (food) and our Energy Expenditure (metabolic rate and activity). Quite basically, if you eat more than you burn you will gain weight. If you burn more than you eat you will lose weight. Weight maintenance is a state of equilibrium between Energy intake and Energy expenditure.
Further to this, there is much evidence to suggest that there is more to weight maintenance than just Energy Balance. Whilst this is a crucial factor, considering portion sizes and the calorie content of our food choices is not the whole picture. By ensuring that you eat a range of fruits and vegetables, some quality protein, a small level of fats and sufficient complex carbohydrates to fuel you and your central nervous system through the day, you have the best chance of enjoying the benefits of your hard work. Similarly, maintaining hydration and getting adequate rest will aid you in your endeavours.
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