Obesity has long been defined as an epidemic and has been linked to a variety of diseases including diabetes, high blood pressure, heart disease, cancer and negative psychological and social conditions. The causes of obesity are numerous and complex, including evolutionary, genetic, hormonal, social, cultural, and psychological factors.
Except in cases of metabolic or hormonal disorders, in most cases the amount of body fat is determined primarily by the caloric balance between the energy we intake (food) and the energy we expend for basic metabolic processes and physical activity.
The daily caloric expenditure is determined by three variables:
- Resting metabolic rate (RMR), which accounts for about 70% of total energy expenditure.
- Physical activity, which accounts for about 20% of total energy expenditure.
- The thermic effect of food the energy required to process consumed food which accounts for about 10% of total energy expenditure.
Since an average person in Western countries spends most of the day in a resting physiological state (sitting or lying down), which contributes about 70% of daily caloric expenditure, the ability to increase metabolism at rest is a focus for many professionals. Here are several common “facts” about metabolism that need to be reexamined:
A. Metabolism depends mainly on body composition, sex, and age.
Not accurate.
Research shows about a 20% variation among individuals that is not explained by these variables. Therefore, common formulas are not precise, and metabolic testing is recommended.
B. Increasing muscle mass will significantly raise resting metabolism.
Not accurate.
Although muscle mass is a significant and active component of daily resting energy expenditure, accounting for about 40% of body mass, each kilogram of muscle burns only about 15 kcal per day (roughly half a teaspoon of sugar or two grams of fat).
By contrast, one kilogram of liver or brain tissue burns about 200 kcal per day.
Therefore, an increase in muscle mass, especially for non athletes or non-bodybuilders, contributes relatively little to metabolism.
C. Physical activity increases resting metabolism.
Not accurate.
High-intensity exercise can temporarily affect metabolism, a phenomenon called EPOC Excess Post Exercise Oxygen Consumption, meaning increased energy use after exertion.
However, despite the cumulative effect of increased energy expenditure after exercise in active people, this has limited impact for several reasons:
- Intense activity is required for any significant contribution.
- After relatively intense activity, EPOC accounts for about 10% of total energy expended during exercise.
For example, after a 30-minute run burning 250 kcal, an additional 25 kcal would be burned during the same day. - Intense, prolonged exercise is a metabolic stress, especially when combined with reduced food intake.
This triggers a natural compensatory response, slowing metabolism and reducing voluntary daily activity.
These mechanisms help explain the difficulty of losing weight during dieting.
D. Increasing meal frequency (small meals each time) raises metabolic rate.
Not true.
There is no scientific evidence for this. However, regular meals at consistent times support metabolic rate more than irregular meals.
E. The effect on metabolism is individual and genetic.
True.
Individuality is a key physiological principle. Different people respond differently to physical activity, nutrition, and other factors, and each case should be assessed with the best available scientific methods.
Conclusion:
There are no shortcuts.
The natural ability to increase resting metabolism is limited.
Extreme measures like intense exercise, very low-calorie diets, and fasting can actually slow weight loss.
To lose weight safely and healthily, engage in regular moderate-intensity exercise, combine strength and aerobic training with any enjoyable movement, gradually reduce food intake, and most importantly, maintain consistency.