While the prospect of living a healthier life certainly motivates a lot of people to engage in some type of regular physical activity, most gym goers also work out because they want to improve their physical appearance. Weight loss is often the primary goal, but how effective is exercise really at promoting fat loss? In this series of posts I’ll look into the history behind physical activity and weight loss, how physical activity influences body composition, the compensatory mechanisms to exercise and how effective aerobic and anaerobic exercise is at promoting weight loss in humans.
Physical activity is considered an important part of a healthy lifestyle, and studies show that regular physical activity can help prevent several chronic diseases (1). Conventional wisdom also entails that regular exercise is effective for someone who’s trying to lose or maintain bodyweight.
It is often suggested that calorie restriction is necessary to lose weight, and that someone who eats whenever desired and as much as desired (ad libitum) won’t lose any weight by exercising more. This notion is based on the belief that the increased energy expenditure during exercise, elevated energy metabolism after exercise and increased basal metabolic rate results in more calories consumed; thereby compensating for the calories burned during exercise (2).
The human body adapts in order to make it more efficient at handling various types of stimulus. Weight training promotes muscle growth and strength gains, and it’s often assumed that aerobic exercise induces fat loss so the body can improve it’s aerobic performance.
Despite the general belief that exercise is effective for someone who’s trying to lose weight, studies on isolated exercise or a combined approach of both exercise and diet show mixed results. It’s well established that diet is the most important modifiable factor in regards to weight management, but is exercising for weight loss worth the sweat?
In the 1950s, the French-American nutritionist Jean Mayer was one of the first to propose a relationship between physical activity and weight management. Prior to the 1950s there were few studies done on the relationship between bodyweight and physical activity, and not many overweight and obese individuals were recommended to exercise more.
Jean Mayer showed through his studies that people with a sedentary lifestyle usually have a higher body mass index, and he quickly became a leading spokesperson in the field of fitness and public health. Since then, physical activity has become synonymous not just with a healthier life, but with a leaner physique, and most medical doctors, personal trainers and health and fitness “gurus” recommend exercise for someone who wants to lose weight. However, the scientific literature is showing mixed results and some argue that the link between inactivity and overweight doesn’t prove causality (3,4).
All posts in this series on exercise and weight loss
Part 1: Introduction and history
Part 2: How does physical activity affect bodyweight?
Part 3: Physical activity, increased appetite and food intake
Part 4: Exercise and weight gain
Part 5: How much do I lose?
Part 6: Summary, discussion and conclusions