Balancing Cardio Training and Diet-induced Weight Loss
Many physique athletes take things to 
extremes. Dieting and training are no exception. Too often you’ll see an athlete performing hours upon hours of cardio and/or reducing calories to half of what they consumed in the off season in an attempt to get super lean. It sometimes seems to become a contest of who can suffer the most. As if the more cardio they do or the more restrictive their diet the leaner and better they will look when it’s time to compete. If this was true the answer to achieving the best contest condition would be simple. If you’re not lean enough, simply add more cardio and drop the calories. Sometimes that may be the answer… but not always.
Although cardio training is certainly an effective method to enhance fat loss it is important to know how much is too much so that you can benefit by losing fat without sacrificing lean muscle tissue. Calorie restriction is also effective for fat loss but can result in inadequate nutrient intake and poor health. Too much of either can result in less muscle, lower metabolic rate, and impaired performance and health. None of these will help you to reach your best look or your best condition.
The relationship between muscle and metabolic rate
A person’s basal metabolic rate (BMR) represents the Calories needed to maintain bodily functions at rest. Total energy expenditure (TEE), is the total amount of Calories a person uses throughout the day, which includes BMR (the largest contributor to TEE), Thermic Effect of Food (the Calories needed for digestion and absorption of foods), and Thermic Effect of Activity (Calories used during exercise).
When researchers performed a cross-sectional study to evaluate the variance of BMR based on lean muscle mass and fat mass they found that the dominant factor influencing variation of BMR was due to lean muscle mass; and that increased BMR was due to increased lean muscle mass (Johnstone et al., 2005). Therefore, maintaining lean muscle mass and lower body fat composition may lead to increases in BMR (Johnstone et al., 2005; Muller et al., 2009) This is critical for athletes who seek a leaner more muscular physique and emphasizes the value of finding the correct balance of a calorie restricted diet and exercise-induced energy deficit-especially in the contest phase of training.
Negative energy balance equals weight loss
The amount of calories that you expend and consume determines whether or not you lose weight. Your body stores most excess calories as body fat REGARDLESS of their source. Expending more calories than you consume each day depletes your body's energy sources, forcing it to mobilize and metabolize body fat to meet any excess energy demands. By expending more calories than you consume each day, you can gradually reduce your body fat percentage. If you expend 500 more calories than you consume each day, you can lose approximately 1 lb. of fat per week.To create a caloric deficit that increases your chances of burning fat, you can either increase your exercise-induced energy expenditure, decrease daily caloric intake or a combination of both methods. 
It’s important to note the KIND of calories the body gets may also affect how efficiently you burn your body's energy.
It's not that calories don't matter but the QUALITY of the calories consumed CAN have an effect on the number of calories expended. For more information on this topic you can refer to my article on the thermic effect of macronutrients.
http://teamvic.com/cms/?p=156
Exercise-induced energydeficit vs. Diet-induced energy deficit
The advantage of using cardio to create an exercise-induced deficit is that it allows you to consume more calories. This is a reasonable alternative for athletes that are currently consuming a relatively low amount of calories. For these individuals the ability to reduce or restrict caloric intake is limited. For example, a female who is currently consuming 1500 calories per day and wants to lose 1lb per weekwould need to reduce her caloric intake to an average of 1000 calories per day. This low daily caloric intakewould make it difficult to consume an adequate amount of nutrients for recovery, health and performance.
Alternatively, a 140lb woman could perform 50 minutes of cardio exercise to burn approximately 500 additional calories which would allow her to MAINTAIN her1500 calories per day.
However, relying solely on extra cardio to create an exercise-induced deficit can be detrimental as well. Too much cardio training can lead to elevated cortisol levels, hinder recovery and result in loss of muscle tissue. All of these factors could contribute to a higher percentage of body fat. And since lean muscle mass is 
the major determinant of metabolism, contributing anywhere from 60% to 80% of BMR (Muller et al., 2009) less lean muscle mass would result in a lower BMR (Muller et al., 2009). In addition, performing too much cardio could leave you fatigued and depleted which cancompromise the ability to train hard with weights. Again, not what you want if you’re trying to maintain lean mass.
Therefore, another solution could be to combine some calorie restriction let’s say an average of 250 per day with the addition of 20-30 minutes of cardio for an additional 250 calories. That said,women generally should not attempt to lose more than ½-1 pound per week in order to avoid muscle wasting.Any more than that is likely water or muscle tissue. In this case the athlete could begin by reducing calories by an average of 250 per day and adjust the rate of weight loss by supplementing with 20-30 minutedaily bouts of cardio training. In my opinion, this is perhaps the most practical approach.
Dieting’s effect on metabolism
Research indicates that restricting caloric intake for fat loss may also lead to decreased BMR. Researchers evaluated 99 overweight or obese participants in the Preventing Overweight Using Novel Dietary Strategies (POUNDS) LOST randomized clinical trial to evaluate BMR after weight loss. The researchers found that the average weight loss of 8.1 kilograms (3.7 pounds) reduced BMR by 136 Calories per day (Bray et al., 2012).
Reductions in metabolism, however, can be countered through exercise, especially the incorporation of resistance training and weight lifting-something physique athletes already do. In fact, researchers assessed the effect of aerobic training, resistance training or no exercise training and found that resistance training conserved lean muscle mass and BMR compared to those who participated in aerobic training only or did not train at all (Hunter et al., 2008).
Based on all of this information, a diet-induced calorie deficit is a reasonable approach for weight-training athletes who are currently consuming a relatively high daily caloric intake. For example, an athlete who is consuming 3500 calories per day could reduce daily caloric intake by an average of 500 per day-resulting in an average daily caloric intake of 3000. The result would be a 1 pound per week weight loss without the addition cardio training.In order to adjust the rate of weight loss, this athlete could either reduce calories an additional 250-500 calories/day or add 20-30 minutes of daily cardio training throughout the week.
Note: Men should strive for a weight loss of no more than 1.5-2 pounds per week in order to avoid sacrificing lean mass.
Conclusion
It is critical for athletes to find the correct balance of a calorie restricted diet and exercise-induced energy deficit. Although adding cardio is certainly effectiveit is important to knowhow much is too muchso that you can benefit by losing fat without sacrificing your hard-earned muscle.On the other hand, calorie restriction is also effective but could result in inadequate nutrient intake and hinder performance in the gym. Paying close attention to your weight, strength and energy levels will help you determine when to make adjustments. However, finding the appropriate balance requires some trial and error and depends on multiple variables.The most practical approach for most athletes is to moderately reduce calories and supplement training with a moderate amount of cardio exercise in order to adjust the rate of weight loss.
Train Smart and Good luck!
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