Aerobic and anaerobic are basic energy systems which body utilizes to produce Adenosine Triphosphate (ATP), which is used by the muscles to contract.

Aerobic

The Aerobic System produce unlimited amount of ATP by utilizing carbohydrates, proteins or fat as long as oxygen is present. The Aerobic system provides medium to very long duration energy production with low to moderate power (less than 85% of maximum output). The products, which are used in this system, are heat, water and carbon dioxide. Aerobic capacity is the ability of the body to collect and transfer oxygen from the air through the lungs and blood to the working muscles. Aerobic capacity is related to cardio-respiratory endurance and is referred to as Maximal Oxygen Consumption or VO2 max. Aerobic Capacity reduces at about 10% after a decade.

Fat can only be used for fuel in the presence of oxygen and oxygen is only used in longer duration aerobic activities. The question is; does it matter if you're burning fat or carbohydrate for fuel? The answer is yes and no. Any increase in your activity level, regardless of whether it burns fat or carbohydrate predominantly, will have some impact on fat loss. However, it's been my experience that to achieve low body fat levels, you need to burn as many calories from fat as possible by performing longer duration exercise at a moderate to moderately high intensity level. Choosing the proper type of aerobic exercise will help you to burn the most calories from fat and achieve maximum fat burning in the shortest time.

Anaerobic

The Anaerobic System utilizes only carbohydrates for ATP production and this system does not use oxygen in the metabolizing of its fuel source. The Anaerobic System provides short duration (45 - 70 seconds) and high power. The by-product in the metabolizing of glucose (glycolysis) in this system is heat and lactic acid, the cause of muscle soreness immediately after exercise.

The Anaerobic Threshold is defined as that point where the body cannot find the oxygen demand and its anaerobic metabolism is accelerated. This point varies on an individual basis and depends on fitness level. For healthy individuals, this occurs between 50% and 66% of their maximal working capacity. This would be equivalent to running faster than half speed.

Anaerobic Training is also known as strength training or weight training. Today, all world-class athletes do serious anaerobic training. Every pro sports team has strength and conditioning coach, and meticulously structured training programs have increased athletic performance to levels previously undreamed of. Physicians now recommend anaerobic training for cardiovascular health, improved bone density and other health benefits. In 1990, the American College of Sports Medicine released a new position statement stating that weight training decreased cardiovascular risk factors and was actually good for your health all along.

It was great news for the bodybuilders when the scientific, medical and athletic communities began to support strength training, except for one thing. Many self-proclaimed strength training "gurus" are now taking the other extreme, suggesting that weight training is the best exercise for fat loss and aerobics is some kind of evil muscle-devouring monster. Let me clear this up for the record - weight training is an important part of a fat burning program, but weight training is not "the best" fat burning exercise. The best way to burn fat is the combination of aerobic, anaerobic and nutrition, all directed towards the achievement of a specific, written goal.

The increase in resting metabolism that comes from weight training is not enough to get maximum fat loss for most body types. It's important to realize that the primary fat burning effect of weight training comes after the workout from the increase in BMR and from the increase in post-exercise metabolic rate. During anaerobic training, you are burning primarily sugar. The increase in post-exercise metabolism from aerobic, on the other hand, is relatively small (with the exception of very high intensity cardio). Cardio provides the majority of the fat burning benefits during the workout, because aerobic exercise uses oxygen and is therefore fat-burning in nature. That's why immediately after every 30 minute cardio workout you could accurately say, "I am now leaner than I was a half an hour ago."

All calories burned will have an impact on fat loss because overall calorie balance is what really matters in the long run. However, it's my contention that sustained fat burning, oxygen-utilizing aerobic exercise is critical for fat loss - especially in endomorph body types. If you're the type of person with stubborn body fat, weight training alone is never going cut it.