Some 16.7% of Spaniards are overweight, thus making Spain the second most obese country in Europe after the UK. This high rate of obesity results in increased heart attacks and strokes, liver disease, diabetes, hypertension and some types of cancer, in addition to premature death. But it’s not all bad news: obesity can be prevented and treated with easy strategies like diet and exercise. But what kind of exercise is the most effective for losing some kilos?
The first question someone should ask is, “Do I really need to lose weight?” Because according to a recent study by the Spanish Society for the Study of Obesity, 82.2% of the Spaniards who suffer from obesity do not consider themselves overweight. In spite of this apparently optimistic self-image, everyone should know how to calculate whether or not they are obese.
While it has been strongly criticized, and improved upon by other methods, the body mass index (BMI) is still the main tool for identifying obesity. The BMI is calculated by dividing a person’s weight in kilos by their height in meters squared. For example, a person who weighs 68 kilos and is 1.70 meters tall will have a BMI of 23.5 (kg/m2). The World Health Organization (WHO) has established that a person is overweight if his BMI is equal to or greater than 25, and is obese if the BMI is 30 or more.
Now that you know how to roughly calculate obesity (although there are other obesity indexes), it’s not only time to control your diet but to plan a training strategy that will allow you to slim down if necessary. Common sense, and what we’ve always heard, tell us that “to lose some kilos” the ideal thing is to get out and run, which can be understood as aerobic exercise. In addition, since our muscle cells burn fat during low-intensity activities (walking or slow cycling), it was recommended to do gentle exercise of very long duration. For example walking fast for several hours. But is this really correct? Is only aerobic exercise important for losing weight or is strength training also useful?
To understand that a program of strength training can be more effective than aerobic training when it comes to slimming, we must first understand some concepts about metabolism and bioenergy: energy expenditure is the relation between the consumption of energy, through the food an individual eats, and the energy that his organism needs to carry out his biological functions. Since energy cannot be created or destroyed, but only transformed, all the energy that we’ve consumed but not spent will be stored, normally in the form of fat. On the other hand, if we consume the same amount of nutrients (energy) but increase the energy expenditure through physical exercise or intellectual activity, we’ll reduce this excess energy we consume, thus restoring the balance and preventing it from accumulating. All the slimming strategies (diet, exercise, pharmaceuticals) are based on this search for a balance, or on an imbalance in favor of energy output. Both components –output and consumption– are usually measured in kilocalories (Kcal).
As shown in the illustration, a person’s total metabolic expenditure is the result of three components: basal energy expenditure (BEE), physical activity, and the thermogenic effect of the food. The BEE, which is about 60% of total energy expenditure, is what our body expends at rest, without any kind of physical or mental effort: the energy we produce just by being alive. It depends on sex (men have a higher BEE than women), age (up to the age of 30, the BEE increases, but after 40 it progressively diminishes), muscle mass (the greater the muscle mass, the greater the BEE), height and weight (both determine body surface, which also determines BEE to a large extent). Some 40% of BEE is used to maintain heart, respiratory, kidney and brain functions, while 60% is lost in the form of heat.
In addition, in a person of moderate daily activity, physical activity accounts for some 30% of total metabolic output. This output increases if we increase the intensity or duration of our physical activities. Nevertheless, although physical activity is what tires us out the most during the day, it only represents half of the total energy expenditure compared to the BEE. Finally, 10% of the total energy expenditure comes from the heat produced by food while it is being digested. This expenditure increases when we eat proteins as opposed to other nutrients, but it’s almost impossible to modulate.
Now that we have some basic ideas about metabolism, it’s easy to understand that if we increase the BEE we will obtain a higher expenditure of energy –we will store less energy in the form of fat– than if we increase the amount of physical activity. The most effective way of upping this basal metabolic rate is through a program of strength training that increases our muscle mass. Just so there is no misunderstanding: in exercise physiology when we talk about strength training it doesn’t necessarily refer to the exaggerated weightlifting (which brings an increase in muscle mass) that we associate with the gymnasium and bodybuilding. By means of correct strength training, we increase the size and tone of our muscles and make them more efficient metabolically, so they can consume more fat. Strength training can be carried out with dumbbells, with machines or with the weight of our own body, a technique known as calisthenics.
If, in addition to increasing muscle mass through strength training, we combine it with aerobic physical activity, we will achieve a great total energy expenditure, a synergy that’s more effective for losing weight. In principle, any aerobic activity will help us move toward this objective, but we should take into account the following: those activities in which our muscles support the weight of our body (like walking fast or running) increase energy output more than the exercises in which our weight is supported by something outside the muscles (a bicycle saddle, the pedals of an elliptical machine or the anti-gravitational effect of water when we swim).
To sum up, if we really want to get rid of excess fat –and the BMI will tell us if this is necessary– we should begin strength training. If we combine it with aerobic exercise, there will be an even greater effect. In addition, all exercises in which our muscles support the weight of our body will help increase energy output, thus preventing any excess energy that we consume from being stored in the form of fat.