The Basics:

• A kilocalorie or calorie is a unit of energy. According to the first law of thermodynamics, energy can neither be created nor destroyed. The calories you consume will either be stored in your body or expended as fuel in the metabolism of daily activities.
• Weight gain is from consuming more energy than one is expending or, conversely, weight loss is from consuming less or a negative energy balance.
• Weight loss comes from three sources: water, adipose tissue or fat and muscle tissue. Water tends to stay the same if one maintains proper hydration.

Myth or Truth:

• The Fat – Burning Zone. We have all heard the claim that low-intensity cardio-vascular exercise is the best way to “burn fat.” What does the research tell us?
• Truth: It’s the Amount that Counts!
  • Thompson et al (1998), has confirmed that cardiovascular exercise at lower intensities (50% VO2 max) uses a greater percentage of fat as fuel than at higher intensities (70% VO2 max).
  • However, this research also tells us that as long as the workouts are the same duration, the total energy expenditure will be greater at higher training intensities. The person who is working out at higher intensities is going to burn as many or more fat calories than at lower intensities.
  • The body does not select fat as fuel at lower intensities. For weight loss plans, exercise should focus on greater total volume of exercise.
  • The Caveat: For people who are sedentary or have orthopedic, cardiac or other high health risks, high intensity exercise may be contraindicated. Lower–to-moderate- intensity exercise should be performed for progressively longer durations. It is advisable to consult a health provider that is familiar with medications and health parameters to initiate an exercise program.

Does Cardiovascular Exercise Make You a Better “Fat Burner”?

• Truth: Yes, it does.
  • There is improved extraction of oxygen via blood flow that helps burn fat more efficiently.
  • There is improved release of fatty acids – triglycerides or saturated fats that are broken down – into the blood and the muscle due to sensitivity of epinephrine or as it is more commonly known as adrenaline.
  • An improved circulatory blood flow aids in the delivery of fatty acids. This allows the amount of fatty acids entering the muscle to increase and making it more available for fuel.
  • Mitochondria or cells that are sometimes referred to as “fat-burning furnaces,” are increased in number and size.

Does Weight Training Help with Weight Loss?

• Truth: Yes, it does.
  • Weight Training or resistance training helps with the maintenance of muscle mass. According to research by Andrew Hill (2004), has shown that diet only weight loss programs can lower a persons resting metabolic rate (RMR) by 20% which can mean that roughly 300 fewer calories are expended during the day. This research demonstrates that resistance training has a protective mechanism that helps maintain the RMR during calorie-restrictive weight loss programs.

Are Carbohydrates the Preferred Energy Fuel?

• Truth: Yes, they are.
  • Carbohydrate is the most important fuel source for exercise – both anaerobic and aerobic. The body prefers carbs to fats during endurance exercise for two key reasons: carbohydrate breakdown or glycolysis is much more efficient than those of fat breakdown. The reason for this is the efficiency with which carbohydrates are broken down (glycolysis) versus fat breakdown. Also, it takes more oxygen to burn fat than carbohydrates. The energy yield of fat from 1 liter of oxygen is 4.69 calories, as compared with a yield of 5.05 calories from carbohydrates. Therefore, carbohydrate is approximately 7% more efficient as fuel.

Does Exercise “Afterburn” Help Burn Fat?

• Truth: Yes, it does.
  • Exercise Afterburn or Excess Post Exercise Oxygen Consumption or EPOC refers to the number of calories expended above resting values after a workout. Both cardiovascular and resistance programs can elicit 65 -150 calories of primarily fat calories post-workout. This number does depend on the intensity of the workout. This may not seem like a significant amount of calories, but over the course of time, these numbers start to have some impact on calories expended.

The facts are in ... to burn more fat, you need to burn more calories!  Exercise plans that consistently burn more calories, either through more strenuous workouts; easier, longer duration workouts; or a combination of the two, will help you become a more efficient “Fat Burner.”

References

Bryner, R. W., et al. 1999. Effects of resistance vs. aerobic training combined with an 800 calorie liquid diet on lean body mass and resting metabolic rate. Journal of the American College of Nutrition, 18 (1), 115-21.

Hill, A.J. 2004. Does dieting make you fat? British Journal of Nutrition, 92 (Suppl. 1), S15-18.

Horowitz, J., & Klein, S. 2000. Lipid metabolism during endurance exercise. American journal of Clincial Nutrition, 72 (2, Suppl.), 5585S-63S.

Kravitz, Len. 2007. Idea Fitness Journal, 23-25.

Thompson, D.L., et al. 1998. Substrate use during and following moderate- and low-intensity exercise. Implications for weight control. European Jouranl of Applied Physiology and Occupational Physiology, 78(1), 43-49.
 

- Donna Schneider, CES, CPT, CEAS