Why can't I lose weight and you can't get fat?

Who doesn't have a co-worker, friend or partner who doesn't know what it's like to eat a salad, snack on fruit or skip dessert out of necessity. It is those people who eat without restraint and, with the rails full and holstered in their tiny carvings, release that phrase that the interlocutor feels like a scratch on the face: "It is that I do not fatten anything". There are, they are not a myth, just as others exist, to which losing three kilos costs endless sacrifices – not to mention how quickly they recover them. Let's say that both types of people inhabit the same planet and go to the gym the same days a week, what does such inequality respond to?

Part of the riddle lies behind a sentence that will be familiar to you: "I have fast metabolism," the ones blessed by the free buffet wand often say. And they're not going off the road. Bartholomew Burguera, president of the Institute of Endocrinology and Metabolism at the Cleveland Clinic in Cleveland, Ohio, USA, recalls that the basal metabolic rate (the calories the body burns at rest due to the functioning of its organs) accounts for 75% of the body's energy expenditure on sedentary subjects, or 60% for those who exercise frequently. "A person with a higher basal metabolic rate can eat 300 extra calories [100 grams of chips, two slices of pizza or a packet of cookies] without gaining weight," he notes.

Núria Vilarrasa, specialist in Endocrinology and Nutrition at Bellvitge University Hospital (L'Hospitalet de Llobregat, Barcelona) and coordinator of the Obesity Group of the Spanish Society of Endocrinology and Nutrition (SEEN), lists the factors contribute to acceleration: "The greater lean or muscle mass, the higher the resting energy expenditure. Certain periods of life, such as childhood, lactation or pregnancy, also increase the basal metabolic rate, which is reduced with aging. Episodes of fever could trigger it, as well as a very active thyroid gland." The latter disorder is called hyperthyroidism and, although it is associated with weight loss, its prevalence is low, recalls Ramón de Cangas, dietitian-nutritionist of the Spanish Academy of Nutrition and Dietetics: only between 0.3% and 1% of the population you suffer from that excessive secretion of hormones that speeds up metabolism. Similarly, hypothyroidism (when the thyroid does not produce enough for the normal functioning of the body) cannot be blamed for a relevant weight gain, "as usually that slowing of metabolism adds only between 2 and 5 kilos", notes the Dr. Vilarrasa.

If it's not an anomaly, where the hell is the trick?

One wonders whether those who gobble up without noticeable consequences on the scale are implementing secret tringules to speed up their metabolism (you know, the classics "drink cold water," "drink more spicy food" or "take a teaspoon of cinnamon every day. ", all real examples read in Spanish media). Burguera responds: "There are no approved techniques or products that do so without endangering health with tachycardias and other adverse effects." In fact, the most common is that this store will slow down during a weight loss process, hence the tricky thing of maintaining a weight loss over time. "By reducing calories, basal energy expenditure decreases as the concentration of orexígen hormones involved in increasing intake increases, and satiety is reduced," says Vilarrasa. That is, his body confies so that it gets fat again.

So, is there anything that does work and that we can control? "Increase muscle mass", proposes Juan del Coso, director of the Laboratory of Exercise Physiology at Camilo José Cela University (Madrid). "This is a strategy that the American College of Sports Medicine (ACSM) already recommends to overweight people, as it is a way to expend energy during the 23 hours a day when no sport is played." And move. Eye: Physical activity (movement to dry) accounts for 30% of energy expenditure in active individuals. And while the planned exercise is the most cost-effective weight loss strategy (nothing to lose weight like soaking the T-shirt), a study from the Mayo Clinic in Rochester, USA, showed that the weight difference between 20 subjects who were considered potatoes from sofa lay in which the thinner ones sat 2.5 hours less a day than the slightly obese. That is, although one thinks that he does the same little exercise as an acquaintance with a couple of sizes less, the most time we spent repantingines in front of the computer or the TV also counts as a bun filled with cream, confirms Del Coso.

The DNA lottery

There are five factors that, according to the obesity researcher Claude Bouchard, predispose to overweight: 1. Little muscle mass. 2. Lack of exercise. 3. Low testosterone levels. 4. Take longer to be satisfied due to hormones. 5. Have the body generate more energy from glucose rather than fat. Of these, the first two can be regulated by religiously paying the gym's monthly fee - eye, the first month does not notice much. (And it's the only safe way that science supports metabolism, even if you already comb gray saives, don't expect miracles, "because from 25 to 75 years old, we tend to gradually lose 11 kilos of muscle in exchange for 12 fat," says Ramón de Cangas , PhD in Functional Biology and Molecular Biology from the University of Oviedo).

The third factor, which negatively affects lean tissue, "should be evaluated individually by the doctor, who will administer, if necessary, a testosterone replacement treatment," explains Burguera, who dictates some of the causes they lead to this deficit: stress, alcohol, advanced age, sleep apnea or opiate and steroid consumption. Of the other two points, forget: there is little you can do. Some organisms simply work better overfood than others.

De Cangas speaks: "A classic study by Claude Bouchard is the best example to visualize that genetics influences the ease or not of losing or gaining weight. In this research, she was given an extra contribution of 1,000 kilocalories to genetically equal twins over 84 days. The weight gain, though not exactly the same, was similar among siblings, but when comparing the twin pairs it was seen that there were significant differences [between 4 and 12 kilograms]." Subsequently, the dietitian-nutritionist continues, numerous studies have linked certain genetic variants to different dietary responses: "For example, the interaction of the APOA5 gene with ingested fats causes some individuals not to benefit from their reduction. And variants of the PLIN gene have been described that make some people more resistant to losing weight with caloric restriction."

The chops you ate as a child count

Another metabolism that should not be lost of sight is the bacteria, that of the millions of bugs that swarm through our stomach and that can be decisive for being overweight. "Debug dietary toxins; synthesize necessary micronutrients such as vitamins K and B12 or folic acid; are involved in the absorption of electrolytes and minerals; and are fermented in indigestible substances," says Constanza Ballesta, Deputy Director of the Obesity and Diabetes Surgery Unit of the Dr. Ballesta Laparoscopic Center, located in the Teknon centre of Barcelona. "In addition, several studies show that intestinal flora also determines the effectiveness in extracting energy from food, and that it depends on a greater or lesser tendency to transform it into adipose tissue," says Ballesta. And it provides figures: subjects with pro-obesity microbiota have an energy absorption of 120-130 kcal/day higher than those without. "To this direct effect, we must add another: the secretion of hormonal substances that increase appetite," he adds.

But why are there people with such a hostile microbiota? "The newborn's maternal lifestyle and first feeding influence," he replies. Although if you feel the urge to call your mother with an air of outrage, stop: what you're eating now is also key. "Dietary factors are changing the composition of the microbiota. A diet rich in protein and animal fats will bring a higher proportion of bacteria that are not beneficial than other vegetarians rich in carbohydrates, fiber and plant protein," the expert says.