Ki Fit

Introduction
Exercise is no longer just exercise, it’s so much more. We now talk a language of reps, sets, intensity, frequency, duration, load, fat-burning, muscle-building and most of all, weight. Although there are countless strategies and approaches in weight management programs, the three overall objectives should include:

 An aerobic and resistance exercise plan to increase caloric expenditure and maintain fat-free (muscle) mass

 A lifestyle/dietary approach emphasising balanced nutrition with an appropriate calorie deficit

 Important guidelines on how to make positive behaviour changes in exercise and lifestyle habits, as well as how to make positive changes for life

In terms of exercising for weight management, the most controversial (and abused!) claim is that you should “exercise in the fat-burning zone to maximise weight-loss and fat utilisation”. Well, what exactly is the “fat-burning zone” and what is the best exercise? There are numerous opinions out there, which seem to confuse fitness professionals and the general population alike. Below is a quick look into the world of “fat burning” and how exercise is related.

Energy Balance Basics
What the First Law of Thermodynamics teaches us is energy is neither created nor destroyed. Since a kilocalorie (kcal or sometimes just ‘calorie’) is a unit of energy, this means that the calories we eat will either be stored somewhere in the body or expended for fuel in metabolism for daily activities, occupational tasks and/or exercise. This basic caloric rule is that you should eat what you burn to maintain weight, and if you want to gain weight you should eat more than what you consume (positive energy balance). For weight loss, a negative energy balance is needed, where energy expenditure is more than energy consumption.

What is often not explained is that when in a negative energy balance, the weight loss may come from three body sources: water, adipose tissue, and muscle tissue. Generally, body water remains relatively normal, given regular hydration, which leaves adipose and muscle tissue. It is not advisable to lose muscle mass as this has a large influence on the resting metabolic rate and affects overall calorie expenditure. Therefore, the goal of the weight loss should always be to lose fat while preserving muscle mass.

The Claim – “Low Intensity Exercise is Better for Fat Burning”
How many times have you heard this? Well research has shown that exercise at lower intensities (50% VO2max) does use a greater ratio of fat to carbohydrate than at higher intensities (70% VO2max). However what is important to highlight is higher training intensities have a greater TOTAL energy expenditure, and a person will almost always burn the same amount (or more) fat calories as seen during lower training intensities, providing the workouts are the same length in time. Basically this means that even though fat is the primary fuel during low intensity exercise, this does not necessarily indicate greater fat loss. This is particularly important when considering weight loss plans. The greater total calorie burn resulting from the exercise is going to have more impact on weight loss, and essentially add to workout efficiency, i.e. greater calorie burn for less time spent. It’s important to remember however, that for those who are sedentary and carry orthopaedic, cardiac or health risks, high intensity exercise may not be appropriate. If this is the case, longer duration lower-intensity exercise becomes more important. In fact, since most people can’t do ‘high intensity’ exercise on a daily basis due to potential overtraining and over use concerns, perhaps the best strategy is to integrate and balance the long duration workouts with the high intensity workouts for optimal calorie (fat) burning.

Resistance Training – fat burner?
Research has confirmed that the most important benefit of resistance exercise in a weight loss program is the preservation of muscle mass. In addition to this, other research has shown that diet only programs can lower a person’s resting metabolic rate (RMR) by 20% (which may be approximately 300 less calories expended per day) and resistance training is one of the best protective interventions to maintain the RMR during a caloric restrictive weight loss program.

Exercise ‘after-burn’ helps fat burning
The exercise after-burn, or EPOC (excess post-exercise oxygen consumption), is the number of calories expended above resting values after a workout. Although intensity dependent, both aerobic and resistance training programs may elicit an EPOC from 65-150 (primarily fat) calories post workout, and can last up to 6 hours. It has been suggested that since one pound of fat is roughly equal to 3,500 calories, EPOC is an insignificant factor in the fat burning process. However, if you consider someone who is training regularly, over a couple months this can be quite meaningful!

The last drop – “To burn more fat, burn more calories!”
So the good news is that your body can become more efficient at burning fat with the right training. However, remember that the TOTAL calories you burn are more important for weight loss than whether you are burning more fat or carbohydrate during exercise. Use a combination of aerobic training and resistance training to balance your exercise plan, preserve muscle mass and maintain resting metabolic rate.

References:
Bryner, R.W., Ullrich, I.H., Sauers, J., Donley, D., Hornsby, G., Kolar, M., and Yeater, R. (1990). 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: 115-121.
Hill, A.J. (2004). Does dieting make you fat? British Journal of Nutrition. Suppl 1, S15-S18.
Horowitz, J. and Klein, S. (2000). Lipid metabolism during endurance exercise. American Journal of Clinical Nutrition, 72: 558S-563S.
Thompson D.L., Townsend K.M., Boughey R., Patterson K., and Bassett D.R. Jr. (1998). Substrate use during and following moderate- and low-intensity exercise: implications for weight control. European Journal of Applied Physiology and Occupational Physiology. Jun;78(1):43-49
Len Kravitz, Ph.D. Fat Facts