Chapter 22:
Exercise and fat loss
Having examined the physiology behind the different types of exercise, it is time to
examine the effects of exercise on fat loss. 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.
Section 1: Caloric expenditure during and after exercise
Calorie burned during exercise
Most exercisers tend to overestimate the number of calories expended during exercise (1).
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 (2).
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.
The loss of one pound of fat requires a calorie deficit of 3500 calories. At five to ten calories
per minute, 300 calories would require 30-60 minutes of aerobic exercise at least three times per
week. This bare minimum expenditure would only be expected to yield 800-900 calories/week
deficit and fat loss would only occur at about 1 lb per month (assuming no other changes in diet or
activity). Some authors have used this to argue against regular exercise, claiming that this small
amount of caloric expenditure cannot possibly have any effect on body weight.
However, an individual who walked briskly 2 miles daily (expending approximately 200
calories or so in 30 minutes) would expend 1400 calories per week (a little less than 1/2 of a pound
of fat). Assuming no change in caloric intake, this should yield a fat loss of about 2 lb per month,