A common misconception is that increased fat use during exercise will equate to increased fat loss from the body. Unfortunately, this assumption is not supported by research and is contrary to the basic components of the energy-balance equation.
It is the combination of exercise, the number of calories ingested and the amount of protein ingested that determines whether you gain or lose body fat or muscle mass.
Assuming a well-balanced diet, when there is a deficit in the energy intake from food relative to energy used, a person will lose body weight.
When energy intake from food exceeds energy use by the body, the excess chemical energy is used to form fat and a person will gain body weight. That can be expressed in the formula: Energy balance equals energy intake minus energy use.
Energy intake is food and liquid ingested. Energy use is that required for basal metabolism plus physical activity and digestion.
The diet dangers
The proportion of the weight change that is either fat, muscle protein or water depends on the strategy used for weight control.
For example, approaching the need to lose body fat by diet alone is fraught with danger.
When energy intake is reduced, the body decreases its basal metabolic rate. Decreases in basal metabolism have been shown to be as high as 500 kilocalories/day.
This makes it possible for an individual to decrease energy intake and still gain body fat, due to the decrease in basal metabolism.
The bad news of dieting alone for body fat control doesn't end here. Dieting alone also can cause the body to depend more on protein stores as a source of energy.
This decreases the body's lean tissue, which is the most metabolically active, further adding to the decrease in basal metabolism.
The bad news of dieting alone for body fat control doesn't end here. Dieting alone also can cause the body to depend more on protein stores as a source of energy.
This decreases the body's lean tissue, which is the most metabolically active, further adding to the decrease in basal metabolism.
Not only is a loss of lean tissue viewed by society to be aesthetically displeasing, it is also counterproductive for sustained or improved participation in competitive sports or athletics.
Unless this lean tissue is replaced, future episodes of dieting alone will futher decrease lean tissue, and the fat on the body will increase relative to the total body.
Let's get physical
Increasing the physical activity side of the energy-balance equation is vital, not just for adding to energy use, but also for retaining or increasing lean body mass, and preventing large decreases in the pre-diet basal metabolic rate.
The question then becomes how to best increase physical activity and optimize fat loss.
Remember, the body functions on a balance of energy input vs. output. The exercise objective is to expend a number of Kcals of energy that will develop an energy deficit for a given dietary condition.
For most of us, we do not have the time to exercise for two hours doing low- intensity exercise (fast walking) to expend the energy necessary to develop a significant energy deficit.
The fact that most of the energy we use comes from fat during this exercise is irrelevent unless we generate an energy deficit.
An alternate, more sensible, and scientifically supported recommendation is to exercise any way you enjoy, as long as it is greater than 30 minutes and more frequent than four times a week.
Forty-five minutes of more intense exercise, if your health status permits and is cleared by your physician, could expend energy equivalent to two hours of walking, thereby giving you the opportunity to fit this into a lunch break, after work, before breakfast, after dinner, etc.
Use more fat
Furthermore, sustained exercise of a moderate intensity, although associated with a higher risk of injury to muscle or bone than low-intensity exercise, provides a high training stimulus for muscle, bone and the cardiovascular system.
Improving the ability of the muscles and cardiovascular system to tolerate exercise can improve your muscles' ability to use fat, not just during the exercise, but also during the remainder of the day.
The concept of exercising to lose body fat by long-duration low-intensity exercise just doesn't make sense when applying sound principles of exercise physiology.
If you need to lose body fat, then see a physican so your health status can be evaluated, and your risk for complications during exercise assessed.
If everything is satisfactory, then start your exercise by doing things you like doing, and fit these activities into your schedule so that you eventually attain the 45 minutes per session, four sessions per week goal.
This may take several weeks or months, but the important thing is that you are able to sustain this habit.
Eventually, you should start doing your exercise/activity at an increased pace, so that you increase your exercise intensity, and further develop the endurance of your muscles and cardiovascular system.
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