Metabolism and Exercise

 In Nutrition

Making Sense of Metabolism, Exercise and Body Composition

For people who have a health and fitness goal regarding body composition, whether it be putting on muscle, losing weight, or simply maintaining the status quo, it is important to understand how your body breaks down the calories it ingests. There is a lot of information available in books, on tv and on the internet and not all of it is good information. As a result there are many myths concerning the link of exercise and nutrition. Having a basic understanding of how the body converts food to energy is the first step to taking control.

Everything you eat or drink gets processed by the body and turned into energy. Simply put there is a complex process that takes place whenever you eat or drink anything where calories in the food/drink are combined with oxygen to release energy for the bodies use. Everything your body does requires this energy, from simply breathing to running a marathon. You’ll hear people talk about your basal metabolic rate (metabolism) this is referring to the amount of calories your body needs to simply live (breath, circulate blood, cellular function etc.). This rate is dependent on many factors including, weight sex and age. Hence, your basal metabolic rate is fairly consistent and is responsible for the majority of calories you burn in a day.

Physical activity will affect the total amount of calories you burn in a day as well. It is highly variable as it activity can change from day to day or week to week. This is one of the reasons it is important to establish exercise or activity days and plan them into your life making them a habit and a priority rather then something left for your spare time.

Another factor is thermogenesis, this refers to the process of your body breaking down the foods you consume. It takes energy to make energy. This factor stays fairly consistent as well provided a person’s diet is fairly consistent.

Many people may believe that their metabolism is at fault for them gaining weight, more often then not however weight gain is not from a medical problem slowing down metabolism, although it does happen. Weight gain can be extremely complicated as there are a number of factors that can contribute such as genetic makeup, hormonal controls, diet etc. However, at the end of the day everyone will lose weight if they are burning more calories than they are consuming. This is why I tell people, and as a personal trainer this sounds counter intuitive, weight loss is 90% nutrition and 10% exercise because exercise cannot compensate for a faulty diet.

Think of the three factors listed above, your basic metabolic rate, the amount of energy you burn turning food into energy, and exercise. Exercise is the most variable of the three, so establishing a healthy diet to meet your basal metabolic rate and the needs for turning food to energy should be the priority. Establishing a healthy exercise program is of course important, but it is not enough on its own.

There are various ways to use exercise to lose weight for example jogging, strength training, or through activities and sports. So which is the best? There are many differing opinions here depending on who you read and which studies you look at. But here are some important factors to consider:

Muscle burns more than fat: I am not saying you need to go out and train to look like Arnold but muscle requires calories and influences your basal metabolic rate. Fat does not need calories, it is simply stored calories. Hence, putting on some lean muscle mass will increase the amount of calories you need, which will make creating a deficit easier. Resistance (strength) training also burns calories as you are doing it, things like circuit training can keep your heart rate up which will increase the amount of calories you burn in an exercise session.

Oxygen Intake: A good way of estimating how many calories you are burning in a workout is related to MET’s (Metabolic Equivalent Task). This method uses the energy cost of activities by monitoring oxygen consumption during exercise. A list for various activities can be found here. Basically if you don’t want to get fancy about it, pick exercises that use large muscle groups, legs for example as they require more oxygen and blood flow which increases the amount of calories the body needs to complete the activity.

Aerobic Exercise: There are a number of ways to get an aerobic workout, this may include a brisk walk, jogging, circuit training or bicycling for example. Try to aim for 30 min 5-7 times per week.

Lifestyle Activities: Sports, gardening, walking the dog etc. are all activities that will increase the amount of calories you burn. It’s important to get into the gym and exercise, but also find an activity(s) that you enjoy that will get you up and active. This will only help when combined with diet and exercise changes.

As complicated as the internet, friends and television can make weight loss out to be, making good nutritional choices, establishing an exercise routine and finding some active activities to do are your best chance at not only losing weight but keeping it off. Everyone wants the magic bullet, the one exercise or diet to fix everything but that’s not how the body works. To truly change and reach your goals it is about recognizing the challenge, gaining an understanding of your body and how it functions, making a commitment to yourself, and establishing healthy diet and exercise habits. This can seem daunting but remember, no one else is going to do it for you, it is not a race, be proud of every success or bit of progress no matter if it is big or small and enjoy the journey, try to find activities, exercise and foods that you enjoy, but that are health for you!

To your success,





Keegan Marshall CPT, CES, MMACS

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Nanaimo Personal Trainer, Nutrition adviceThe word metabolism and associated words and phrases for weight loss