How to Lose Weight by Doing Sports

This article would like to eliminate, once and for all, some clichés that are completely wrong, about the relationship between weight loss andsport (The energy expenditure of running may be useful preliminary reading).

To lose weight, you must sweat

It is ridiculous that there are people who think like this even today. You just need look at someone who runs in a city park, to see that they believe they must cover themselves and sweat as much as possible. They will probably be pleased with themselves when they return home and see that the scale shows two kilograms less, only to discover with despair the next morning that they have returned to their normal weight. Neither does it make much sense not to drink, just to ensure that their weight loss is definite. Eventually they must drink to rehydrate, and the illusion will vanish.

To lose weight you must do sport at a low intensity

This myth was born in the gyms and in all the other environments where they use cardio fitness – to lose weight you must not exceed a certain heart rate!! In these environments, you often find people who want to minimize their fatigue, together with the less conscientious personal trainers that manage to sell strategies that are consistent with the laziness of the individuals. The myth is based on the fact that by doing sports at low intensity, you will give preference to burning fats. The doubt that then follows is about our metabolism: If I run fast, then I will burn carbohydrates and not fat!

Why do many people believe that the running speed is fundamental in weight loss? In reality, this is a true test of intelligence that will not be passed by those who have an overly simplistic approach to problems.

The basic mistake that is made by those who think that to lose weight you must (note “must”) run slowly depends mainly on two factors:

  1. They do not understand that weight loss depends on the combination of two factors: SPORT & DIET. You cannot stop at what happens while you do sports as you must also evaluate what you do “after”.
  2. They do not know that the carbohydrates ingested by eating will turn to fat if our carbohydrate stores are at the maximum. Each individual has a rather limited maximum storage of carbohydrates, unlike fat that continues to accumulate.

losing weightFUNDAMENTAL REASONING! – First of all, we must not consider our body as hermetic compartments. Our body knows extremely well how to transform fat into energy and carbohydrates into fat. Therefore, it is not the case that if we eat carbohydrates, they will be stored as carbohydrates; just as fats do not necessarily end up around the waistline. The body uses the macronutrients to adapt itself to the energy it requires.

Let us assume that an individual maintains his weight with 2,000 calories per day, 200 of which are needed for physical activity. If the activity is mild, the body will burn preferentially fat, (the fat burned at low intensity is very substantial, but it always burns a portion of carbohydrates). If the physical activity is intense, it will burn carbohydrates. At that, the geniuses will ask: why do we burn carbohydrates and not fat if we run fast? The crucial thing to understand is that 300 of the 2,000 calories that we eat (regardless of whether we have taken them in the form of fats or carbohydrates), will go to substitute the energy that has been lost by running. The 300 calories will substitute the fat that we have lost if we have burned fats, and likewise, if we have burned carbohydrates they will go to replace the reserves of carbohydrates (glycogen). In both cases, the subject maintains their weight: They can only lose weight if they take in less than 2,000 calories per day.

In other words:

  1. If we run very slowly, we will burn fat. We lose weight because it decreases our stockpile of fats;
  2. If we run fast, we burn carbohydrates, but we prevent the carbohydrates that we consume in our diet being stored as fat. We lose weight because we deviate the carbohydrates from going to the belly, and we employ them as energy for physical activity.

What if I am on a diet? – Let us suppose that a person, who maintains their weight with 2,000 calories, decides to assume 300 calories less (those that are normally consumed by physical activity) but does sport at high intensity and, therefore, burns primarily carbohydrates. You might think that there would not be any calories to go towards replacing the stockpile of lost carbohydrates, but you would fall back into the example of bogus weight loss: the person loses weight because they empty their carbohydrate reserves.

Actually, it is not like this. We must remember that there are carbohydrates contained in the 2,000 calories. If the person wants to slim down, then they will be slightly overweight – unless they are masochists. Let us suppose that of the 2,000 calories consumed, 1,200 calories are carbohydrates, 300 calories are proteins, and 500 calories are fats. It is a perfect example of someone who follows the Mediterranean diet. They weigh 65 kg (which justifies 2,000 calories of which 200 calories are for sport), and they would like to lose 4 – 5 kg. The amount of carbohydrates is excessive in this individual, (as it is in 90% of the population) and they transform them into fat on a daily basis. In fact, their daily requirement of carbohydrates is about 169 g (2.6 * P), which we then multiply by 4 to get the calories, 676 calories. If our subject reduces his daily intake by 300 calories, then he would consume 1700 calories distributed as follows: 1,020 of carbohydrates, 255 of proteins and 425 of fats. 676 calories of the 1,020 calories of carbohydrates consumed will be used in their metabolism, 300 in restoring the stocks of carbohydrate, and 44 calories will still be turned into fat. If we compare this to the original situation, then only 44 calories are converted into fat as opposed to 344 calories. Therefore, our subject will lose weight and not their carbohydrate reserves. Moral: the 300 calories that we reduce in our diet, prevent the carbohydrates that are eaten from being converted into fats; instead, they go to restore the carbohydrate reserves with the subsequent effect of lowering the reserves of fats.

From the figures reported above, it must also be obvious that those who want to lose weight cannot undertake monstrous efforts (like a marathon) without eating decently afterwards since they risk burning their stored glycogen or, above all, the proteins of their muscles. However, this danger is severely limited by the fact that those who are seriously overweight do not have enough training for this kind of effort.

What about hunger? – Some advocates of low-intensity exercise claim that by running fast, you burn a lot of carbs, lower the blood sugar and trigger hunger pangs. These people have probably never done high intensity sport and do not know that after such a strain, the body is busy restoring its many resources that have been lost through physical activity, and that you do not feel hungry. The appetite gradually returns and replenishes, little by little, the correct amount of calories.

Hunger arrives instantly with low-intensity sports because the appetite is not only related to glucose (as the proponents of low-intensity training naively believe): It should be enough to remember the after effects of a pleasant walk in the mountains!

To lose weight you must run fast

Generally speaking, you must use the maximum effort if you want to lose weight. This is the opposite of the last error. There are those who believe that the faster you run, the more fat you will burn, but the increase in the basal metabolic rate of the vast majority of people is not significant enough. I know from physics that the amount of work is given by the effort of the movement. It is not so much the weight, but the mechanical effort of our musculoskeletal system in moving it forward, working parallel to the movement. In a rough way, think of a hand that pushes a person forward. The speed with which the work is done (the power) has nothing to do with the total work. The mistake in believing that the speed is important comes from the fact that we confuse the power (work per unit of time) with the work itself. Consider a world champion who weighs 60 kg and runs 20 km in an hour. They will have consumed approximately 1,200 calories. A beginner of the same weight that travels 10 km in one hour will burn 600 calories, half the amount: going faster makes you burn more calories per unit of time. If our beginner runs 20 km (it will take twice the amount of time: two hours), they will also burn 1,200 calories.

A human is not like a car. The faster a car goes, the more fuel it consumes. We always use the same amount of energy to travel a kilometre regardless of our speed. So it is better (for weight loss) to do 22 km at 5’/km than 20 km at 4’30″/km.

The right strategy

Since calorie expenditure depends on the kilometres that you run, it is obvious that

you must choose the speed that allows the greatest number of kilometres in the time available if you want to lose weight.

NOTE – The preceding sentence must not be interpreted as starting as fast as you canand then trying stoically to resist. It means that you must be able to distribute your energy, according to your level of training, in a way that allows you to travel the longest distance. For example: the beginner who does not have the legs for an hour of running, but has one hour available, can alternate between running and walking, in order to maximize the kilometres that they cover.

Clothing should be as light as possible: Another error that people make is covering themselves up too much – we recover the sweat that is lost by drinking during the day – but even the unpleasant sensation of heat makes us stop earlier and cover fewer kilometres.

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