Fitness recommendations

Alternative names

Physical activity; Exercise

Definition

Physical activity is any activity that causes your body to work harder than normal. However, the actual amount of physical activity you need depends on your individual fitness goals, whether you are trying to lose weight, and how fit you currently are.

Information

Physical activity can help you:

• Burn calories and reduce body fat.
  
• Reduce your appetite.
  
• Maintain and control your weight.
  

For the purpose of weight loss, physical activity works best when you also reduce your intake of calories.

The number of calories burned is dependent on:

• The amount of time spent on physical activity. For example, walking for 45 minutes will burn more calories than walking for 20 minutes.
  
• Your body weight. For example, a 250-pound person will expend more energy walking for 30 minutes than a 185-pound person.
  
• Pace: For example, walking 3 miles per hour will burn more calories than walking 1.5 miles per hour.
  

BASAL METABOLIC RATE

Your basal metabolic rate (BMR) is the number of calories used by your body when it is at rest. BMR accounts for most of your calorie use. Your basal metabolic rate is based on body functions such as breathing, digestion, heartbeat, and brain function. Your age, sex, body weight, and level of physical activity impact the basal metabolic rate. Basal metabolic rate increases with the amount of muscle tissue you have, and it reduces with age.

Along with burning more calories, physical activity increases the BMR, and the BMR can remain increased after 30 minutes of moderate physical activity. For many people the basal metabolic rate can be increased 10% for approximately 48 hours after the activity. This means, for example, even after the physical activity, when a person is sedentary and watching television, the body is using more calories than usual.

EFFECT ON APPETITE

Physical activity at a moderate rate does not increase the appetite. In some situations, the appetite will actually decrease. Research indicates that the decrease in appetite after physical activity is greater in individuals who are obese than in individuals who are at their desirable body weight.

LOSS OF BODY FAT

When losing weight through calorie reduction alone, a person loses 25% of his or her lean body mass and 75% of his or her body fat. Combining calorie reduction with physical activity can result in loss of 98% of body fat. Weight loss that is achieved with a combination of calorie restriction and physical activity is more effective. For maintenance of desirable body weight, a maintenance level of calories along with physical activity is recommended to preserve lean body mass and muscle tone.