Ask an Expert: Exercise to increase metabolism

Q: How much time do I need to devote to exercise each week to make a positive impact on my metabolism?

Answer provided by Mike Boggs, BS, MBA, CSCS (certified strength-conditioning specialist), fitness specialist, Providence Fitness Services: 

Let’s start by talking about what metabolism is and how it works. Metabolism is the process of converting food into calories, which our bodies then burn for fuel. Our metabolic rate is the number of calories our bodies burn in an average day.

If we burn more calories through activity than we take in, we lose weight over time. If we take in more calories than we burn, we gain weight over time. This is known as managing the difference between "calories-in" and "calories-out." 

We can manage our calories-in by choosing a well-balanced, well-portioned nutrition plan to fuel our bodies. Eating small, frequent meals helps speed the metabolism. Restrictive diets, meal-skipping and other drastic calorie-cutting measures only serve to slow down the metabolism. It is crucial for your body to get enough calories each day (a minimum of 1,200 per day for women and 1,500 per day for men).

On the calories-out side of the equation, our bodies burn calories in three distinct ways:
  • Resting metabolism
  • Food digestion
  • Physical activity

Resting metabolism provides the energy the body needs to pump blood, inhale and exhale air, control temperature, send and receive nerve impulses, and manage brain activity. Strange as it may seem, the largest percentage of calories we burn each day are used for such "resting" activities.

Our bodies also burn a small number of calories each day as they digest, absorb, transport and store food. We are limited in our ability to affect the rate at which our bodies burn calories through resting metabolism or food digestion.

The area in which we can make the greatest impact on calories-out is physical activity. Physical activity includes exercise as well as other activities that engage muscles for movement. The number of calories burned during physical activity and exercise varies from person to person, and also depends on the type, intensity, and duration of the activity.

A combination of cardiovascular, strength, and flexibility exercises is the best approach to a well-rounded fitness program.

Cardiovascular exercises (such as walking or swimming) are among the best forms of activity to enhance caloric expenditure and maintain or lose weight. A great way to make sure we are getting enough cardiovascular exercise each week is to use the FIT Principle (Frequency, Intensity, Time), which addresses how often, how hard, and how long we need to exercise aerobically each week:

  • F=Frequency: We need to exercise aerobically three to six times each week.
  • I=Intensity: We need to exercise aerobically at a moderate to moderately hard pace.
  • T=Time: We need to exercise aerobically 20 – 40 minutes each session.

As individuals with different fitness levels and different goals, we need to adjust the FIT Principle to meet our needs. This might include adding a day, increasing time, or modifying intensity.

November 2003