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Family Health Magazine
ACTIVE LIVING

Jump Start Weight Loss
Using physical activity to boost metabolism

If your weight loss program has stalled, maybe you need a jump start. Physical activity is key to boosting your metabolism. Whether you are just starting to lose weight or want to maintain it, increasing your metabolic rate through exercise can help.

Metabolic rate

Your body needs a certain amount of energy to function every day. This energy comes in the form of calories. A basal or resting metabolic rate is the number of calories you must use for essential bodily processes – organ and tissue function, sleeping and breathing. Typically, this accounts for 60 per cent of all calories used.

Calories also give energy for movement and activity, like making dinner or walking to work. The average person burns about 30 per cent of calories this way. Finally, dietary thermogenesis is the energy used to digest and process food you eat. This accounts for about 10 per cent of our energy needs.

Think of it as energy in and energy out. If you consume and use 2500 calories a day, your weight remains the same. If you want to lose one pound (0.45 kilogram) of fat, then you must lower your food intake by 3500 calories, or increase energy use by burning 3500 calories over time. By eating less and lowering your dietary intake each day by 500 calories, you can sensibly lose about a pound a week (500 calories x 7 days = 3500 calories). Mathematically, this all works out. However, other factors influence metabolic rate.

Influences on your metabolic rate

You can control some factors related to energy intake and use, such as:

• foods eaten - how often, how much and what type
• energy expended while gardening or hiking
• maintaining your body composition (ratio of muscle mass to fat mass).

You cannot control other factors, including:

• age
• genes
• and gender.

Burning energy

The first step in increasing energy use is choosing an activity that you can do successfully. Many health care providers suggest walking. Regardless of what you choose, the key is making it happen. When starting off, it is more important to do an activity often, rather than for a long time.

You might begin with 20 minutes of walking, three times a week. After a month or roughly four weeks of walking you will have established your exercise behaviour or routine. Now, progressively increase the duration by 10 per cent each week. In week five, walk 22 minutes three times a week, the next week 24 minutes, and so on. By the time your walks last 30 minutes, you will be burning about 150 calories more per day. This equals about a third of a pound (0.15 kilogram) of weight loss each week.

Getting FITT

Once you reach 30 minutes per session, exercise physiologists suggest adding a fourth element – intensity - to your scheduled exercise.

F = Frequency

I = Intensity

T = Type of exercise

T = Time or duration

By ramping up intensity, you increase your heart rate. You can do this two ways. First, you could increase your speed to cover more distance in the same amount of time. Or two, add a few hills into the route and try to keep the same pace.

Whatever your choice, you will lose more weight and burn more calories by doing moderately intense activities:

• Walking: start with 1 mile in 20 minutes (3 mph) or 120 to 135 steps per minute and increase to 4 mph
• Running: start with 1 mile in 12-16 min (5 mph) and increase to 6 mph
• Bicycling: start with 10-11.9 mph and increase to 12-13.9 mph.

Muscle mass

Intensity makes a big difference to your use of calories. Muscle mass is the tissue that really increases metabolic rate. Muscle mass is eight times more metabolically active than fat tissue at rest. Using large muscles can increase energy expenditure from five to ten calories per minute. For instance, adding walking poles to your 30-minute walk increases the use of muscles from the abdominal, shoulder and chest area. More calories are burned, since you have increased your exercise load and the number of muscle groups involved.

Becoming more metabolically active

As muscle contracts, it produces heat. After exercise, it takes time to return to a pre-active state. This means that when you stop exercising, your muscles keep burning calories for a few hours after your workout is completed. This is called post-exercise oxygen consumption. A recent study showed that moderate to high intensity activity boosts resting metabolic rate by about 15 per cent.

Gender and muscle

Men on average have more muscle mass than women. As we have already stated muscle mass is responsible for burning fat even when the body is at rest. Hormonally, women have much higher quantities of the female hormone estrogen in their systems than do men. Estrogen is responsible for hanging on to body fat to prepare the body for pregnancy. Research shows that as women tend to be more energy efficient, this is also a factor as to why some have a harder time losing weight.

Aging and muscle

You cannot control the way that aging affects metabolic rate. With each decade that passes, you need about two per cent fewer calories. However, maintaining body composition does suppress the effects of aging. By training with weights and/or resistance three times a week for 20 minutes, you will build muscle. For every extra pound of muscle you gain, your body uses around 50 extra calories a day. Added muscle mass also burns more calories at rest, offsetting the aging effect on a slowing metabolism. Remember a combination of activities in your exercise routine is best since aerobic activity is good for your cardiovascular system and strength training is great for maintaining your muscle mass.

Calories and fuel use

We know that higher intensity exercise boosts calorie use. What kind of fuel or energy source is best? High intensity or anaerobic (short bursts) strength training typically uses more carbohydrates. During post-exercise recovery, energy use rises for two to fifteen hours. To meet energy needs, your body burns more calories – a good portion of which will come from stored fat.

Some researchers say this effect is so small that it does not play a major role in controlling weight loss. However, combining an entire exercise session with proper diet can increase metabolism enough to start and maintain weight loss. Don’t forget energy in and energy out is still important. For instance, reducing your diet by a 100 calories a day can theoretically result in 10 pounds a year of fat loss. Add an activity that expends 150 calories a day and your combined weight loss could be as much as 25 pounds in a year.

Keep your motor running!

Research shows that regular participation in a variety of physical activities is a positive approach to maintaining weight loss and staying healthy. So take every opportunity to keep your “motor running.”