Increase Your Metabolism to Lose Weight and Stay Fit

I STARTED TALKING with an elderly gentlemen on the bus today and he asked me this question, "Why cant I just diet to loose weight? You know, why do I need to exercise? It's so tough." The answer seems very simple - by going on a crash diet you are missing out on a lot of important nutrients, so it's not healthy. But there is also another important reason why it is not advisable to go on a crash diet and why exercising is so important to loose weight.

Our body is continuously burning calories (fuel) to perform its functions. We burn around 70-90 cal/hr while doing a simple task such as sitting. Functions such as breathing, digestion, generating heat (warmth), circulation, require energy. Our vital organs such the brain, heart, liver and kidney are continuously utilizing energy, that is burning calories.  Another important organ that is highly metabolically active is our muscle. Our muscle requires energy to do even the slightest movements.  On the other hand, adipose tissue (fat tissue) is not metabolically active. It does not utilize calories at all.

Some important definitions and concepts:

• The amount of energy that we need to support all basal body functions (everything that we need to support when we are asleep) is called the Basal Metabolic Rate (BMR). BMR accounts for nearly 60% of daily energy requirements and is measured after a 12-hour fast.
• The amount of energy that we burn when at rest is called Resting Metabolic Rate (RMR). RMR is measured a few hours after a meal. BMR and RMR differ by about 3-5%.
• The amount of energy required for digestion, absorption and processing of nutrients after a meal is called Thermic effect of feeding (TEF). TEF is typically 10% above BMR.
• The amount of energy spent doing activities and exercise is called Thermic effect of exercise (TEE). TEE can really vary depending upon the daily activity of a person.

These are the different ways in which we actually burn the calories that we consume. Looking at the definitions, we can see that TEE is the only value that we can control and vary. When we exercise more and do a lot of physical activity, we burn more calories and TEE increases.

Our BMR also can be varied to a certain extent by exercise. When we exercise, we burn fat tissue and build muscle. So the lean body mass of our body improves. Since muscle is very metabolically active, our BMR increases and we burn more calories even at rest. In contrast if we don’t exercise, muscle content of our body will be low. Hence BMR also will be low and we do not burn a lot of calories at rest.

So putting it all together, it is important to exercise or do some kind of physical activity in addition to being on a restricted calorie diet to loose weight, because

• Exercising helps in increasing lean body mass  and decreasing fat mass.
• Increased lean body mass will increase our BMR, allowing us to burn more calories even when at rest.
• Increased lean body mass provides body strength and fitness.

All these benefits cannot be achieved just with a weight loss diet. Those of you out there really trying to lose weight or even trying to remain fit - make sure you get about 120 minutes of exercise each week.

Eat healthy, be active and stay healthy!

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Srilekha Karunanithi of Kirkland is a first-year Master's student in Nutritional Sciences at University of Washington who is training to become a Registered Dietitian. Her master’s program focuses on the influences of diet on health and how positive dietary changes help in the control and prevention of many diseases.