Scientific American

This is a collection of articles from Scientific American, which means that they are full of high-quality information and research, but it also means that some are more readable than others, and some resonate more than others. For me, the section covering transgender science and medical care was the strongest and most impactful. Of particular interest was the research into a biological basis for transgender and nonbinary identities.

Tras tres años trabajando para la Comunidad de Madrid en asuntos de nanotecnología (NT), algo he aprendido. Y es que no se puede dejar que los periodistas hablen de ella sin tener que entrar a matizar después. Les desafío a que encuentren un artículo periodístico sobre nanotecnología que no contenga la palabra “revolución”. La NT es, a grandes rasgos, el conjunto de tecnologías que para su funcionamiento requieran que una de las dimensiones de los dispositivos mida entre 1 y 100 show more nanómetros. En un milímetro entra un millón de nanómetros en fila india, por lo que estamos hablando de dimensiones muy reducidas. Para ser sinceros, a día de hoy hay muy pocos objetos que incorporen nanotecnología de forma perceptible. De momento, los avances se han realizado sobre todo en el campo de la ciencia de materiales, logrando aleaciones y compuestos que pesan menos y resisten más que sus contrapartes “macrotecnológcas”. Por ejemplo, Toyota usa desde hace unos años un compuesto de polímero y arcilla (Polymer-clay Nanocomposite) para los estribos de los todoterrenos, que no sufre apenas desgaste. Los proyectos a medio y largo plazo de la nanotecnología son, de momento, parte de la ciencia ficción: robots que entran en el torrente sanguíneo y destruyen las células cancerígenas una a una, superficies que se limpian solas… miles y miles de aplicaciones que parecen, de momento, lejanas. En este libro se nos instruye en los rudimentos de la NT (sin entrar en la mecánica cuántica que subyace) a través de varios artículos disjuntos. El libro no está mal, es básico, introductorio y sencillito. Mi nota: Interesante show less

I guess the thrust of this collection of articles from Scientific American could be summarised in a few sentences; basically they are saying that it’s really hard to lose weight and keep it off by exercising and people who work really hard don’t burn many more calories than a couch potato. And dieting is not easy for a whole host of psychological and biochemical reasons. In both cases, the underlying recommendation is to make small changes but stick to the regime. One thing that I did show more find missing in this book was any discussion of a change to a vegetarian diet or whole plant based food diet as recommended by T Colin Campbell. In fact, most of the diet changes discussed seem to be related to single constituent changes....like low carbs or high protein. etc. Each article is written by a different writer (or several writers).
Overall. I was not greatly impressed. I don't think I learned much that was new...a few things certainly....but it is pitched at a fairly low level of knowledge and there is no evidence there of any disagreements with the modest changes approach. No debate. A bit disappointing. Here are a few extracts that grabbed my attention:

1.1 The Exercise Paradox
Researchers in public health and human evolution have long assumed that our hunter-gatherer ancestors burned more calories than people in cities and towns do today. Given how physically hard folks such as the Hadza work, it seems impossible to imagine otherwise.....Hadza men ate and burned about 2,600 calories a day, Hadza women about 1,900 calories a day—the same as adults in the U.S. or Europe. We looked at the data every way imaginable, accounting for effects of body size, fat percentage, age and sex. No difference. How was it possible? What were we missing? What else were we getting wrong about human biology and evolution?
Comparing energy expenditure and physical activity in rural Nigerian women with that in African-American women in Chicago. [The survey] found no differences in daily energy expenditure between populations, despite large differences in activity levels. ...In 2013 Australian researchers found similar energy expenditures in sheep and kangaroos kept penned or allowed to roam free.
On average, couch potatoes tended to spend about 200 fewer calories each day than people who were moderately active: the kind of folks who get some exercise during the week and make a point to take the stairs......People with the most intensely active daily lives burned the same number of calories each day as those with moderately active lives. All of this evidence points toward obesity being a disease of gluttony rather than sloth. People gain weight when the calories they eat exceed the calories they expend.
Evidence indicates that it is best to think of diet and exercise as different tools with different strengths. Exercise to stay healthy and vital; focus on diet to look after your weight.
Our brains are so large that, as you sit reading this article, the oxygen from every fourth breath you take is needed just to feed your brain.
We had found in that study that primates burn only half as many calories a day as other mammals do......The reduced metabolic rates of primates correspond with their slow rates of growth and reproduction.......Sure enough, humans burn more calories each day than any of our great ape relatives. Even after accounting for effects of body size, activity level and other factors, humans consume and expend about 400 more calories a day than chimpanzees and bonobos do; differences with gorillas and orangutans are larger still. Those extra calories represent the extra work our bodies do to support larger brains, produce more babies and maintain our bodies so we live longer.
Human evolution was not entirely without trade-offs: our digestive tract is smaller and less costly than other apes, which need a large, energetically expensive gut to digest their fibrous, plant-based diets......Our mastery of fire converts otherwise inedible root vegetables—from Trader Joe’s yams to wild Hadza tubers—into veritable starch bombs.
Problematic though it may be in our modern era, our propensity to store fat most likely coevolved with our faster metabolism as a critical energy buffer to survive lean times.
Sharing food is so fundamental to the human experience, the common thread of every barbecue, birthday, bar mitzvah, that we take it for granted, but it is a unique and essential part of our evolutionary inheritance. Other apes do not share.

1.2 The Messy Truth about Weight Loss
Some 600 million, or 13 percent, of the world’s adults were obese in 2014—a figure that had more than doubled around the globe since 1980.....If fad diets, reality television programs and willpower could make a dent in the problem, we would have seen a change by now.
We have shown, for example, that exercise is not the most important thing to focus on when you want to lose weight—although it has numerous other health benefits, including maintaining a healthy weight.....what you eat and how much you eat play a substantially greater role in determining whether you shed kilograms. An adult male of healthy weight and typical height living in the U.S. today requires about 2,500 calories per day to maintain his weight, whereas the average non-obese adult female requires around 2,000 calories. (Men tend to use more calories because, on average, they have larger bodies and greater muscle mass.)
Species as diverse as red deer and gray seals require two to three times more calories, kilogram per kilogram, than primates to maintain their size....The Hadza people in northern Tanzania, a group of hunter-gatherers, and found that the men needed 2,649 calories on average per day. The women, who—like the men—tend to be smaller than counterparts in other regions, needed just 1,877. Another study of the indigenous Yakut people of Siberia found requirements of 3,103 calories for men and 2,299 for women. And members of the Aymara living in the Andean altiplano were found to require 2,653 calories for men and 2,342 calories for women.......On average, Americans consume 500 more calories
each day than they did in the 1970s.
Eventually the researchers determined that the body can extract about four calories of energy per gram from proteins and carbohydrates and nine calories per gram from fat. (These numbers are now known as Atwater factors.).....Raw whole almonds, for example, are harder to digest than Atwater would have predicted, so we get about a third fewer calories from them, whereas we can metabolize all the calories found in almond butter.
So we and others have proved that not all calories are equal—at least for nuts and high-fiber cereals.
Physical activity is responsible for only about one third of total energy expenditure (assuming a stable body weight). The body’s basal metabolism—that is, the energy it needs to maintain itself while at rest—makes up the other two thirds.....Intriguingly, the areas of the body with the greatest energy requirement are the brain and certain internal organs, such as the heart and kidneys—not the skeletal muscle,
Metabolic rate also differs among individuals.....But let us suppose that you have started to lose some weight. Naturally, your metabolic rate and calorie requirements must fall as your body becomes smaller, meaning that weight loss will slow down.....Studies show that metabolic rate drops somewhat more than expected during active weight loss.
the role of hunger has long been to keep us alive. Thus, there is no point in fighting it directly.
Single-meal feeding tests by several labs, including our own, show that meals higher in protein or fiber or those that do not cause a sudden spike in blood sugar (glucose) levels are generally more satisfying and better at suppressing hunger.....calorie consumption in the hours following a breakfast with a so-called high glycemic index (think highly processed breakfast cereals) was 29 percent greater than after a morning meal with a low glycemic index (steel-cut oatmeal or scrambled eggs).
Differences in the hunger-reducing properties of foods, the efficiency with which they are absorbed and the real, though limited, ability of our metabolism to adapt to changes in energy intake make weight management a complex system.....It has been well established that the majority of individuals who are obese secrete proportionately higher levels of insulin, the hormone that helps the body to metabolize glucose. This so-called insulin resistance leads to a host of other metabolic problems,
When we placed such people on a six-month weight-loss program featuring more protein and fiber, fewer carbohydrates and a low glycemic index, we found that they lost more weight than they could on a high-carbohydrate diet with a high glycemic index.
People with low insulin levels, in contrast, did equally well on diets that were higher or lower in the ratio of proteins and carbohydrates, as well as in glycemic index.

1.3 The “True” Human Diet
The “True” Human Diet by Peter Ungar
it’s no surprise that Paleolithic diets remain hugely popular. There are many variants on the general theme, but foods rich in protein and omega-3 fatty acids show up again and again. Grass-fed cow meat and fish are good, and carbohydrates should come from nonstarchy fresh fruits and vegetables. On the other hand, cereal grains, legumes, dairy, potatoes, and highly refined and processed foods are out. The idea is to eat like our Stone Age ancestors—you know, spinach salads with avocado, walnuts, diced turkey, and the like.
From the standpoint of paleoecology, the Paleolithic diet is a myth. Food choice is as much about what’s available to be eaten as it is about what a species evolved to eat.
What was the ancestral human diet? The question itself makes no sense. Consider some of the recent hunter-gatherers who have inspired Paleolithic diet enthusiasts. The Tikiġaġmiut of the north Alaskan coast lived almost entirely on the protein and fat of marine mammals and fish, while the Gwi San in Botswana’s Central Kalahari took something like 70 percent of their calories from carbohydrate-rich, sugary melons and starchy roots.

1.4 Mind over Meal: Weight-Loss Surgery and the Gut-Brain Connection
Connection by Bret Stetka
Teresa had undergone a sleeve gastrectomy, one of a variety of procedures—known as bariatric surgeries—that manipulate the stomach and intestines to promote weight loss. Yet more than shedding pounds, which she did, it was the complete change in cravings that Teresa considers the most surprising result of her 2012 operation.
Teresa’s weight loss was in all likelihood caused by the drastic change in how her gut speaks to her brain, and vice versa. The procedure had indirectly spurred new neural connections, changing how she thought about and craved food.
Recent science has revealed that appetite, metabolism and weight are regulated through a complex dialogue between bowel and brain—one in which mechanical influences, hormones, bile acids and even the microbes living in our gut all interact with labyrinthine neurocircuitry.
Conversely, the gut can send signals back to the brain, too. In fact, coursing through our abdomen is the enteric nervous system, colloquially known as the second brain. This neural network helps to control food digestion and propulsion through the 30 feet of our gastrointestinal tract. It also communicates directly with the brain through the vagus nerve, which connects the brain with many of our major organs.
Two primary gut-brain pathways regulate appetite. Both systems involve a small, central brain region called the hypothalamus....The first system comes into play during fasting. The stomach secretes the hormone ghrelin, which stimulates a region within the hypothalamus called the arcuate nucleus. This structure then releases neuropeptide Y, a neurotransmitter that, in turn, revs up appetite centers in the cerebral cortex, the outer folds of the brain, driving us to seek out food.
In anticipation of mealtime, our brain sends a signal to the stomach via the vagus nerve, readying it for digestion.....The second gut-brain pathway suppresses our appetite. As we eat, several other hormones, including leptin and insulin, are secreted from fat tissue, the pancreas and the gastrointestinal tract. Separately, these hormones play many roles in digestion and metabolism. Acting together, they signal to another area of the hypothalamus that we are getting full. Our brain tells us to stop eating......Hunger pathways also interact with brain regions such as the amygdala, involved in emotion, and the hippocampus, the brain’s memory center. Hence, our “gut feelings” and “comfort foods” are driven more by moods than mealtimes and nostalgic recollections.......Much like sex, drugs, gambling and other vices, food can cause a surge of dopamine release in the brain’s reward circuitry.
Research has shown that in the days and weeks after bariatric surgery, sugary, fatty and salty foods become less palatable.....The alteration in cravings and taste may be caused by changes in the release and reception of neurotransmitters throughout the gut-brain system.
Palmiter’s work suggests that engagement of the brain stem parabrachial pathway helps us curb our appetite. Because it is this same pathway that becomes unusually active postsurgery, it is probable that the hyperactivation Berthoud discovered is part of the gut-brain’s effort to assess satisfaction postsurgery. As he puts it, “the brain must relearn how to be satisfied with smaller portions.”
There is another player in the complex communications of mind and gut that might explain bariatric surgery’s effects. Experts have implicated the microbiota.
The fact that rodents could lose weight without surgery, simply by receiving microbes from their postoperative fellows, suggests that these microbial populations may be at least partly
Specific gut microbial populations can trigger hormonal and neuronal signaling to the brain such that they influence the development of neural circuits involved in motor control and anxiety. Bäckhed suspects gut flora after bariatric surgery could have a comparable effect on brain regions associated with cravings and appetite.
The neurotransmitter serotonin could play a special role as well. About 90 percent of our body’s serotonin is produced in the gut, and in 2015 researchers at the California Institute of Technology reported that at least some of that production relies on microbes.
In 2015, for example, the U.S. Food and Drug Administration approved a device that stimulates the vagus nerve to quell food cravings.....That approach offers some patients a less invasive alternative to bariatric surgery, but for the moment, vagus nerve stimulators are not as effective as many other obesity therapies.....Acosta Cardenas’s findings support the idea that there are clear subclasses of obesity and that the cause and ideal treatment of obesity is most likely unique to each patient.

2.1 Don’t Diet!
by Charlotte N. Markey
A huge amount of scientific evidence tells us that dieting does not promote lasting weight loss. In fact, many dieters end up gaining back more weight after they quit. Such strategies hardly ever work because they are too extreme and thus almost impossible to maintain over the long term.
My advice as a psychologist and researcher who focuses on weight control: Do not diet.
Making small changes to your eating patterns, ones you can build on slowly over time, is truly the best pathway to lasting weight loss. Although you may have heard this message of moderation before, the evidence is finally too overwhelming to ignore.
Once you give into temptation after restricting yourself, you are more likely to binge.
Vow to avoid pasta, and you will soon find yourself dreaming about spaghetti.
Food preoccupation is an inevitable result of dieting. Psychologists call this phenomenon “ironic processing”—suppressing a thought makes it more salient.
Many studies over the years have shown that people who try to eliminate food groups end up craving those foods intensely.
In fact, treating yourself to indulgences may help you avoid the pitfalls of craving and overeating forbidden foods.
dieters have more difficulty learning new information, solving problems and exerting self-control.
women who restricted their caloric intake and recorded what they ate exhibited elevated cortisol levels, a marker of biological stress.
If you want to improve your body, you must also improve your mind-set. Decades of research show that individuals who are dissatisfied with their bodies are less successful at losing weight. Studies also show that it is possible for anyone to learn to feel good about his or her body.
you need to make gradual, sustainable changes to your diet: for example, drinking less alcohol and juice, substituting diet soda or seltzer for regular soda, and eating dessert on four nights a week instead of seven.
A large body of research supports the idea that making simple, gradual changes to your eating patterns is the best way to promote lasting weight loss....The best tactics, according to the seminal 2006 report, included self-monitoring, such as limiting certain foods, keeping track of portion sizes and calories, planning meals and incorporating exercise into the daily routine.....People who plan their meals are 1.5 times more likely to maintain their weight loss. When combined with better eating habits, however, exercise appears to help people slim down. Incorporating exercise into your life should be a gradual process.
Receiving social support is key to losing weight. Consulting a physician or nutritionist is one way to elicit support and provide greater accountability. Research also demonstrates the role romantic partners play in encouraging weight loss.

2.2 Behaviour: The Additional Key to Weight-Loss
Behaviour: The Additional Key to Weight-Loss by David H. Freedman
A review in 2007 by the American Psychological Association of 31 diet studies found that as many as two thirds of dieters end up two years later weighing more than they did before their diet.....In its strategic plan for funding obesity research, published in 2011, the NIH placed at the top of the list of research opportunities the investigation of basic biological processes related to obesity......The work has also given pharmaceutical companies numerous potential targets for drug development. What the research has not done, unfortunately, is make a dent in solving the national epidemic.
An obesity fix cannot be boiled down to eating certain kinds of food or taking other simple actions. Many factors contribute to the problem. Some are environmental—the others are biological, such as genetic predispositions....Economics and marketing play roles, too.
Junk food is much cheaper than fresh produce.
The most successful way to-date to lose at least modest amounts of weight and keep it off is with diet and exercise
A systematic review sponsored by the U.S. Preventive Services Task Force concluded that even brief behavioral-counseling interventions reduced the number of drinks taken by problem drinkers by 13 to 34 percent for as long as four years. Programs based on behavioral principles are more likely to help people take and keep the weight off than other approaches. ....A number of researchers have turned their attention in recent years to improving, expanding and tailoring behavioral techniques, with encouraging results.
It is too soon to say whether the public will accept government efforts to push it toward healthier choices. San Francisco’s ban on Happy Meal toys was initially vetoed by the mayor in response to angry reaction....Efforts by Let’s Move to bring healthier food to school cafeterias have been intensely criticized by some as overly intrusive. The courts threw out New York City’s ban on large sodas.....And voters have rejected taxes on high-calorie beverages in San Francisco and most other cities and states that have proposed them.

3.1 Head Strong
Head Strong by Ferris Jabr
The fact that exercise improves physical health is so well known as to be a platitude. Decades of research demonstrate that regular exercise lowers the risk of many illnesses—heart disease, obesity, diabetes, cancer—and extends the average life span.....In contrast, the benefits of exercise for mental health are not quite so obvious or well publicized.
In the case of depression, the collective evidence to date suggests that the answer is an emphatic yes.....It appears to combat depression in a number of ways: by strengthening our biochemical resilience to stress, encouraging the growth of new brain cells, bolstering self-esteem and possibly even counterbalancing an underlying genetic risk for mental illness.
Major depression—an illness characterized by a persistent low mood or loss of interest in typically pleasurable activities, often accompanied by insomnia, fatigue, poor concentration or feelings of worthlessness—is one of the leading causes of disability and death around the globe, according to the World Health Organization.....At any given time, it afflicts around 350 million people worldwide and 18 million people in the U.S.
A 2013 review by the nonprofit organization Cochrane, regarded as a leader in evidence-based medicine, concluded that exercise is just as effective a treatment for depression as medication and counseling.....A recent meta-analysis, published in 2016, echoes Cochrane’s finding. A team of international researchers examined 25 of the most rigorous experiments and determined that exercise, especially moderate to vigorous aerobic exercise under professional supervision, is indeed a potent treatment for depression.
“The ideal is probably at least 16 kilocalories per kilogram of body weight, which works out to 1,200 to 1,500 kilocalories each week for average body weight,” Trivedi says. “If you can talk to your spouse on the phone, you’re not working out at the right intensity.”
“Which exercise has the best mood effects, and what intensity is best? Does it work better alone or combined with other treatments? We don’t know for certain yet,” says psychologist Michael Otto of Boston University,
The second you start running, pedaling or lifting a dumbbell, your body’s chemistry begins to change. Exercise boosts your heart rate, sending blood, oxygen, hormones and neurochemicals surging through the body. In the moment, the body responds to exercise as a kind of stress—but it is ultimately beneficial.
Studies have documented the atrophy and loss of neurons in brain regions such as the amygdala, hippocampus and prefrontal cortex in patients with major depression. Antidepressants that increase levels of serotonin and other neurotransmitters might work by reinvigorating neural proliferation, a process that depends in part on a molecule called brain-derived neurotrophic factor (BDNF). In studies with both animals and people, exercise enhances the production of BDNF.
The authors suspect that exercise enhanced the biochemical effects of the drugs. Similar studies have shown that simply recommending healthy lifestyle changes, such as establishing better sleep routines and getting more exercise, can dramatically boost the efficacy of antidepressants from a mere 10 percent remission rate with the drugs alone to a 60 percent remission rate.
The researchers concluded that by stimulating BDNF production, long-term, vigorous aerobic exercise might actually counteract a genetic susceptibility to depression.
epidemiological surveys suggest that physical inactivity, while sometimes the result of depression, may also be a major risk factor for subsequently developing.....A 2015 survey of nearly 5,000 Chinese college students found that the more time a student spent in front of a TV or computer screen, the more likely he or she was to have depressive symptoms.....In contrast, the risk for depression dropped the more physically active a student was, regardless of age, gender or residential background.....Research suggests that exercise as therapy succeeds when people choose the type and intensity.
Only some health insurance companies pay for gym time, and when they do, they often offer small temporary discounts. “I can prescribe a drug that costs $200 and insurance will pay, but they won’t give $40 to open a gym membership.”

3.2 Take 2 Hikes and Call Me in the Morning
Take 2 Hikes and Call Me in the Morning by Nathaniel P. Morris
A large body of evidence suggests that exposure to nature may promote mental well-being. A 2010 meta-analysis of 10 studies including over 1,200 participants found people who exercised in green environments demonstrated significant improvements in mood and self-esteem.
Researchers are trying to better understand the neuroscience behind why exposure to parks and other natural settings might promote mental health....Multiple studies suggest outdoor exercise may be helpful in treating depression. Nature-assisted treatments have been associated with improved outcomes for conditions like schizophrenia as well as decreased levels of health care consumption among people with mental health issues.
although park prescriptions are popping up across the country, we still have little data to confirm whether these programs have a meaningful impact on patients’ health—mental health or otherwise.
visiting a park has fewer side effects and lower costs compared with some of the medications we give our patients.
Two stars from em. show less

Otro estupendo libro a cuyo espíritu se apuntó CPI. Un montón de lectores mandan preguntas a la revista Scientific American (en español, Investigación y Ciencia), donde cada pregunta es respondida por un especialista en la materia (a veces, incluso, por el premio Nobel cuya investigación respondió a la pregunta formulada).

Hay unas cuantas preguntas, muchas, que son realmente interesantes: ¿Cómo se mide el peso de un planeta? ¿Cómo sobreviven los delfines y las ballenas si se pasan show more el día bebiendo agua salada? ¿Por qué muchos perros y gatos aparecen con los ojos azules o verdes en las fotos con flash, en vez de rojos? ¿Cómo conseguía levantarse el T. Rex con esas patitas delanteras tan pequeñas? ¿Cómo se produce una resaca? ¿Por qué marea leer en el coche? ¿Por qué no hay cáncer de corazón? ¿Por qué en ocasiones el arco iris se ve más grande que en otras?

Es un libro muy cortito pero muy aprovechable. El único defecto que le veo es que a veces las respuestas son demasiado cortas, dejándonos con ganas de más o, en un par de ocasiones, simplificando demasiado. Ejemplo: El cielo es azul porque absorbe más el rojo, igual que el agua del mar. Uf.

En cualquier caso, cualquier libro que comparta el espíritu CPI me parece bueno, aquí reconozco que no soy imparcial. El hecho de que muchas preguntas dispares tengan respuestas basadas en lo que la humanidad ha ido observando a lo largo de la historia me parece increíble. Einstein ya lo dijo mejor:

Lo más incomprensible del Universo es que sea comprensible.

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