We all know what makes us bad and what we should avoid. But what makes junk food so irresistibly good?
This is what a listener consulted with the BBC's "scientific detectives", biologist Adam Rutherford and mathematics Hannah Fry, radio program presenters "The Curious Cases of Rutherford and Fry", which is dedicated to investigating the mysteries of everyday life sent by the public.
"Why does bad food taste so good?" Asked Alan Fouracre of New Zealand, explaining that he was referring to things like "sausages, chips and chocolate."
To find out, Rutherford and Fry started looking for material scientist and food lover Mark Miodownik, who explained why are we doing – literally – wetting our mouths when we see these unhealthy foods.
"We have taste for the sweet, the savory, the sour and the bitter, and they all claim to be fired for this food," Miodownik said.
"And (when you eat them) they light. a symphony of flavors (In your mouth)".
But language is not the only guilty of taking us along the nutritional path … the first one that incites us to sin It's our nose.
"What drives our desires is our sense of smell," he said.
The smell of a certain type of food makes our digestive system binds and claim to be fed.
And since the food is in our mouth, it is also our nose that allows us to feel all the subtlety of its flavor.
"They are thousands of flavors, it's very sophisticated," explained Miodownik.
The role of smell explains why many of these foods – for example, a hamburger or fried bacon – are irresistible. when they are hot, but we are no longer interested in cold.
"As the food cools, it loses its flavor because there is less heat turning volatile molecules into odors inside the mouth," said the scientist.
And the soft drinks?
But if heat is an important factor in explaining the attraction of junk food, what about soda, considered one of the main culprits for the rise in obesity in the world?
Or with the chocolate and sweets, which costs us a lot to eat in moderation.
One of the world's most recognized food experts, Professor Linda Bartoshuk of the University of Florida, explained to the program why sugar-rich foods attract so much.
"The fuel for the brain is glucose, which is sweetand throughout evolution, our brains have developed in such a way that they make us love the sweet, because we need it, "he said.
This explains why we go out in search of sweet foods and why we like them so much.
Bartoshuk points out that this connection "comes from birth" and even before: it has been proven that even the fetuses enjoy the candy.
"A pediatrician did a research in the 1920's injecting saccharin into the amniotic fluid of a pregnant woman and the fetus drank the fluid," he said.
Observations indicated that the fetus liked the sweet drink.
Full of receivers
We have already seen how our tongue, our nose and our brain make a plot against our determination to eat healthy. But the challenge does not end there.
Our body has several "taste receptors": not only are they in the mouth, but also in the stomach and gastrointestinal tract.
And these receptors also have their "desires."
"For example, fat and protein can not be detected in the mouth, but you swallow them, your digestive system converts them to fatty acid and glutamate, and now you have receptors in the stomach that tell your brain to get into that fantastic fat and protein" , describes Bartoshuk.
These associations they work unconsciously,so they can lead you to want some kind of food without you knowing or understanding why.
The psychological aspect
Rutherford and Fry also analyzed the attractiveness of unhealthy foods from the psychological point of view.
They found that categorizing this food as "bad" could, in fact, make it more desirable.
"When you rate a meal as bad, you create a guilty feeling of eating it, which leads you to think that which should be particularly enjoyable and it can make it harder to resist, "said Anthony Warner, who writes about food under the pseudonym" The Angry Chef. "
"It's like putting this food on a pedestal and turn it into forbidden food. This will make you want more"he said.
According to Warner, the most guilty people tend to have less control over what they eat and the more difficult to improve their eating habits.
"By calling it evil, you hinder resistance," he said.
So what is the solution to a healthier diet, according to BBC scientists?
"Eat in moderation and enjoy. We need fats, sugars and salty foods. "
"Just do not eat too much."
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