There are a number of misconceptions regarding the role of exercise in fat loss. One of the many misconceptions about is the overestimation of calories burned during and after exercise. As well, there is great debate about the ‘best’ form of exercise when fat loss is the goal. In general, people tend to over-emphasize aerobic exercise for fat loss while downplaying other forms of exercise, such as interval or weight training. Recent research highlights the benefits of weight and interval training for fat loss.

In addition to the type of exercise done, total caloric intake has an impact on fat loss when combined with exercise. At moderate caloric deficits, both weight training and endurance exercise can increase fat loss. However, if caloric intake is too low, exercise can have a negative effect on fat loss.

During aerobic exercise, caloric expenditure averages about 5 calories/minute at low intensities increasing to 10+ calories/minute as intensity increases. As a point of reference, a threshold calorie expenditure of 300 calories three times per week or 200 calories four times per week has been established as the minimum amount of aerobic exercise that will cause fat loss.

Additionally, exercising two days per week does not result in significant fat loss, even if
more calories are expended. Burning 500 calories twice per week (a total of 1000 calories
expended) does not cause the same fat loss as burning 300 calories three times per week (only 900 calories). The body must receive an exercise stimulus at least three days per week. How this stimulus is divided between weights, aerobic exercise and/or interval training will depend on an individual’s goals. Generally speaking, for fat loss, weight training should be performed 2-3 times per week minimum and aerobic exercise of some sort 3 or more times per week.

Simply adding aerobic exercise with no change in diet causes weight loss to occur for men
but not always women. The reasons for this gender discrepancy are not fully understood. Simply put, when women add aerobic exercise without performing resistance training or making changes to their diet, the rate of fat loss is extremely slow.

Muscle is one of the body’s most active tissues and adding muscle can permanently raise
metabolic rate. This is especially important for older individuals who may have lost muscle mass due to inactivity or obesity.

A very prevalent misconception about aerobic exercise is the so-called ‘fat burning zone’
which is supposed to optimize fat loss. It is true that a greater percentage of fat is used during low-intensity exercise. This suggests that low-intensity exercise is the best form of exercise to lose fat. However, due to the low total caloric expenditure, the total amount of fat used is small. As exercise intensity increases (up to about 75% of maximum heart
rate), while the percentage of total calories derived from fat is smaller, the total amount of fat used is greater. The physiology of fuel utilization is that lower intensities rely on fat over glucose, then as intensity increases, glucose is preferred over fat. This ultimately ignores the following fact: the utilization of fat during exercise has little bearing on fat loss. Numerous studies have compared the effect of different intensities of aerobic exercise on fat loss. As long as the caloric expenditure is the same, total fat loss is identical whether the exercise is done at low or high intensity. That is, the fuel used during exercise is of secondary importance compared to the amount of calories expended. As long as more calories are burned than eaten, the body will
reduce fat stores. One thing to note is that as the intensity of exercise increases, the duration of activity decreases. This means that some individuals will burn more calories by using lower intensities but increasing duration, while others will burn more calories exercising at higher intensities for a shorter period of time. Ultimately dieters must find the optimal combination of intensity and duration which maximizes caloric expenditure.

HTH

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