The Mathematics of Obesity

Carson Chow is an investigator at the National Institute of Diabetes and Digestive and Kidney Diseases, where he tries to figure out why 1 in 3 Americans are overweight. He’s an MIT-trained mathematician who is using his background to pinpoint why the obesity rate in America is so high (and will likely keep increasing). His interview in The New York Times is a good read:

Why would mathematics have the answer?

Because to do this experimentally would take years. You could find out much more quickly if you did the math.

Now, prior to my coming on staff, the institute had hired a mathematical physiologist, Kevin Hall. Kevin developed a model that could predict how your body composition changed in response to what you ate. He created a math model of a human being and then plugged in all the variables — height, weight, food intake, exercise. The model could predict what a person will weigh, given their body size and what they take in.

However, the model was complicated: hundreds of equations. Kevin and I began working together to boil it down to one simple equation. That’s what applied mathematicians do. We make things simple. Once we had it, the slimmed-down equation proved to be a useful platform for answering a host of questions.

What new information did your equation render?

That the conventional wisdom of 3,500 calories less is what it takes to lose a pound of weight is wrong. The body changes as you lose. Interestingly, we also found that the fatter you get, the easier it is to gain weight. An extra 10 calories a day puts more weight onto an obese person than on a thinner one.

Also, there’s a time constant that’s an important factor in weight loss. That’s because if you reduce your caloric intake, after a while, your body reaches equilibrium. It actually takes about three years for a dieter to reach their new “steady state.” Our model predicts that if you eat 100 calories fewer a day, in three years you will, on average, lose 10 pounds — if you don’t cheat.

Another finding: Huge variations in your daily food intake will not cause variations in weight, as long as your average food intake over a year is about the same. This is because a person’s body will respond slowly to the food intake.

More here.

Change Your Life in Twenty Minutes a Day

Gretchen Reynolds, author of The First 20 Minutes: Surprising Science Reveals How We Can Exercise Better, Train Smarter, Live Longer, explains how you can change your life in just twenty minutes a day:

The first 20 minutes of moving around, if someone has been really sedentary, provide most of the health benefits. You get prolonged life, reduced disease risk — all of those things come in in the first 20 minutes of being active.

Two-thirds of Americans get no exercise at all. If one of those people gets up and moves around for 20 minutes, they are going to get a huge number of health benefits, and everything beyond that 20 minutes is, to some degree, gravy.

That doesn’t mean I’m suggesting people should not exercise more if they want to. You can always do more. But the science shows that if you just do anything, even stand in place 20 minutes, you will be healthier.

I haven’t read Gretchen’s book, but I am putting her philosophy to use in 2012. My advice: start at just five minutes a day and build up to twenty (or more). It might seem like an insurmountable obstacle in the beginning, which is understandable, but you’ll get there with practice…

Why Being Bilingual Makes You Smarter

This is a good piece in The New York Times on the advantages of being a bilingual:

The collective evidence from a number of studies suggests that the bilingual experience improves the brain’s so-called executive function — a command system that directs the attention processes that we use for planning, solving problems and performing various other mentally demanding tasks. These processes include ignoring distractions to stay focused, switching attention willfully from one thing to another and holding information in mind — like remembering a sequence of directions while driving.

Why does the tussle between two simultaneously active language systems improve these aspects of cognition? Until recently, researchers thought the bilingual advantage stemmed primarily from an ability for inhibition that was honed by the exercise of suppressing one language system: this suppression, it was thought, would help train the bilingual mind to ignore distractions in other contexts. But that explanation increasingly appears to be inadequate, since studies have shown that bilinguals perform better than monolinguals even at tasks that do not require inhibition, like threading a line through an ascending series of numbers scattered randomly on a page.

The key difference between bilinguals and monolinguals may be more basic: a heightened ability to monitor the environment. “Bilinguals have to switch languages quite often — you may talk to your father in one language and to your mother in another language,” says Albert Costa, a researcher at the University of Pompea Fabra in Spain. “It requires keeping track of changes around you in the same way that we monitor our surroundings when driving.” In a study comparing German-Italian bilinguals with Italian monolinguals on monitoring tasks, Mr. Costa and his colleagues found that the bilingual subjects not only performed better, but they also did so with less activity in parts of the brain involved in monitoring, indicating that they were more efficient at it.

The benefits of bilingualism stay with you throughout your life as well. Bilinguals, compared to those who speak one language, are more resistant to the onset of dementia and other symptoms of Alzheimer’s disease.

It’s good to be bilingual.

The One Minute Exercise Regimen

The New York Times reports on the benefits of high-intensity interval training, in which short bursts of very intense activity are followed by short period of recovery:

For years, the American Heart Association and other organizations have recommended that people complete 30 minutes or more of continuous, moderate-intensity exercise, such as a brisk walk, five times a week, for overall good health.

But millions of Americans don’t engage in that much moderate exercise, if they complete any at all. Asked why, a majority of respondents, in survey after survey, say, “I don’t have time.”

Intervals, however, require little time. They are, by definition, short. But whether most people can tolerate intervals, and whether, in turn, intervals provide the same health and fitness benefits as longer, more moderate endurance exercise are issues that haven’t been much investigated.

Several years ago, the McMasters scientists did test a punishing workout, known as high-intensity interval training, or HIIT, that involved 30 seconds of all-out effort at 100 percent of a person’s maximum heart rate. After six weeks, these lacerating HIIT sessions produced similar physiological changesin the leg muscles of young men as multiple, hour-long sessions per week of steady cycling, even though the HIIT workouts involved about 90 percent less exercise time.

Recognizing, however, that few of us willingly can or will practice such straining all-out effort, the researchers also developed a gentler but still chronologically abbreviated form of HIIT. This modified routine involved one minute of strenuous effort, at about 90 percent of a person’s maximum heart rate (which most of us can estimate, very roughly, by subtracting our age from 220), followed by one minute of easy recovery. The effort and recovery are repeated 10 times, for a total of 20 minutes.

Despite the small time commitment of this modified HIIT program, after several weeks of practicing it, both the unfit volunteers and the cardiac patients showed significant improvements in their health and fitness.

The results, published in a recent review of HIIT-related research, were especially remarkable in the cardiac patients. They showed “significant improvements” in the functioning of their blood vessels and heart, said Maureen MacDonald, an associate professor of kinesiology at McMaster who is leading the ongoing experiment.

This is very interesting research and high-intensity interval training is something I’d be willing to try in the gym.

Virtual Reality and Pain Relief

In “Burning Man,” Jay Kirk tells the incredible story of Sam Brown, who was set on fire by an improvised explosive device while on tour in Afghanistan. He survived, only to find himself doomed to a post-traumatic life of unbearable pain. When hallucinogen-grade drugs offered little relief, he turned to virtual reality. And partaking in a video game called SnowWorld helped Sam Brown cope with pain more than anything else he tried:

Last July, Maani and Hoffman published the results of the study in which Sam Brown had participated. Echoing the civilian studies, soldiers reported significant drops in pain while immersed in SnowWorld. Time spent thinking about pain, which is an inextricable contributor to actual pain, dropped from 76 percent without SnowWorld to 22 percent with SnowWorld. Amazingly, some of the biggest drops were for the most severe levels of pain, which went against every previous expectation. Since then, SnowWorld has received a good deal of enthusiasm from several well-lit corners of the Pentagon. At least one four-star general, after seeing the results from the ISR study, has gone so far as to say that he foresees a day coming soon when VR pain distraction might become standard care. There is nearly equal excitement about Hoffman’s other applications, including one called IraqWorld, a virtual-reality exposure therapy he built to treat soldiers with PTSD.

Hoffman knows that more studies need to be done before VR becomes a regular part of a medic’s field kit. To that end, he and his colleagues at HITLab are now using $7.5 million in NIH grants to further investigate how VR affects the mind and how better to apply it in clinical situations. One part of the study is looking at using small doses of ketamine to enhance the sense of presence. But he is confident that eventually, as the technology becomes more sophisticated, VR will be exponentially more effective. Soon, he predicts, VR worlds will be customized, personally tailored, and as in social networks or Second Life, they’ll allow patients to bring along other people—a vet’s mother, girlfriend, buddies. Hoffman imagines programs that will tap into a patient’s happy memories—of a ski vacation or a honeymoon or a morning rowing on a river, sunlight dripping from the oars.

Hoffman can also see battlefield applications. Customized VR worlds will be pre-programmed right into the soldier’s eye gear. He’s already experimenting with piezoelectric crystals to that end. It doesn’t seem like much of a stretch to imagine a near future in which combat patients could simultaneously distract themselves from their own pain while inflicting it on a virtual and remote enemy. A soldier could put his mind inside a drone instead of watching as a medic changed his bandages. In such a future of techno-utopian warfare, at least for those combatants equipped to fight outside the pain matrix, victory will indeed belong to those who have rid themselves of the inconvenience of being men and who, for all we know, may as well bleed snow.

An incredible story.

The Fat Trap

From the latest issue of New York Times Magazine, a discouraging statement for those of us trying to lose weight:

While researchers have known for decades that the body undergoes various metabolic and hormonal changes while it’s losing weight, the Australian team detected something new. A full year after significant weight loss, these men and women remained in what could be described as a biologically altered state. Their still-plump bodies were acting as if they were starving and were working overtime to regain the pounds they lost. For instance, a gastric hormone called ghrelin, often dubbed the “hunger hormone,” was about 20 percent higher than at the start of the study. Another hormone associated with suppressing hunger, peptide YY, was also abnormally low. Levels of leptin, a hormone that suppresses hunger and increases metabolism, also remained lower than expected. A cocktail of other hormones associated with hunger and metabolism all remained significantly changed compared to pre-dieting levels. It was almost as if weight loss had put their bodies into a unique metabolic state, a sort of post-dieting syndrome that set them apart from people who hadn’t tried to lose weight in the first place.

“What we see here is a coordinated defense mechanism with multiple components all directed toward making us put on weight,” Proietto says. “This, I think, explains the high failure rate in obesity treatment.”

While the findings from Proietto and colleagues, published this fall in The New England Journal of Medicine, are not conclusive — the study was small and the findings need to be replicated — the research has nonetheless caused a stir in the weight-loss community, adding to a growing body of evidence that challenges conventional thinking about obesity, weight loss and willpower. For years, the advice to the overweight and obese has been that we simply need to eat less and exercise more. While there is truth to this guidance, it fails to take into account that the human body continues to fight against weight loss long after dieting has stopped. This translates into a sobering reality: once we become fat, most of us, despite our best efforts, will probably stay fat.

As with many preliminary studies, the evidence is inconclusive. Yet, if it pans out, dieting and exercise books will have to be re-written.

Readings: Beyond the Breathalyzer, Guerrilla Girls, Greek Default, Like Culture

Some interesting reads from across the web:

(1) “Beyond the Breathalyzer” [New York Times] – I thought that science was progressing in tracking genetic markings via blood samples, but there’s this:

Scientists are building sophisticated electronic and chemical sniffers that examine the puffs of exhaled air for telltale signs of cancer, tuberculosis, asthma and other maladies, as well as for radiation exposure.


(2) “Guerrilla Girls: Feminist Masked Avengers” [Washington Post] I had no idea about this guerrilla group, and how under-represented women are in the Metropolitan Museum.

Do women have to be naked to get into the Met. Museum? Less than 3% of the artists in the Modern Art sections are women,” the sign continues, “but 83% of the nudes are female.

(3) “Once Greece Goes…” [London Review of Books] – the piece begins with this heavy sentence and picks up from there:

The economic crisis in Greece is the most consequential thing to have happened in Europe since the Balkan wars.


I speak of the Greek default as a sure thing because it is: the markets are pricing Greek government debt as if it has already defaulted. This in itself is a huge deal, because the euro was built on the assumption that no country in it would ever default, and as a result there is no precedent and, more important still, no mechanism for what is about to happen.

The situation in Greece looks grim indeed.

(4) “The Insidious Evils of ‘Like’ Culture” [Wall Street Journal] – this piece is a bit confusing. Does the author want us to like it or not? The author’s conclusions are stuffy: we want to be liked in person, not just online. Still, this contrarian stance is something to think about:

Just as stand-up comedians are trained to be funny by observing which of their lines and expressions are greeted with laughter, so too are our thoughts online molded to conform to popular opinion by these buttons. A status update that is met with no likes (or a clever tweet that isn’t retweeted) becomes the equivalent of a joke met with silence. It must be rethought and rewritten. And so we don’t show our true selves online, but a mask designed to conform to the opinions of those around us.

Your thoughts?

Readings: Shrinking Cities, Oldest Federal Judge, Exercise

A few interesting articles I’ve read over the last couple of days…

1) “How To Shrink a City” [Boston Globe] – many American cities are shrinking in size:

Over the last 50 years, the city of Detroit has lost more than half its population. So has Cleveland. They’re not alone: Eight of the 10 largest cities in the United States in 1950, including Boston, have since lost at least 20 percent of their population. But while Boston has recouped some of that loss in recent years and made itself into the anchor of a thriving white-collar economy, the far more drastic losses of cities like Detroit or Youngstown, Ohio, or Flint, Mich. — losses of people, jobs, money, and social ties — show no signs of turning around. The housing crisis has only accelerated the process.

And so what is to be done? This article offers a glimpse of what some cities, like Detroit, are doing:

In Detroit, a city that now has more than 40 square miles of vacant land, Mayor Dave Bing has committed himself to finding a way to move more of the city’s residents into its remaining vibrant neighborhoods and figuring out something else to do with what remains. A growing number of cities and counties are creating “land banks” to enable them to clear the administrative hurdles that previously prevented them from taking control of blighted blocks of abandoned homes.

2) “At 103, a Judge Has One Caveat: No Lengthy Trials” [New York Times] – an intriguing look into the life of Judge Brown (no, not that Judge Brown), who is the oldest federal judge in the United States:

Born on June 22, 1907, in Hutchinson, Kan., Judge Brown, who had become a prominent local Democrat, first sought appointment by President Harry S. Truman to the federal bench while serving as a lieutenant in the Navy during World War II (at 37, he was the oldest man in his unit). He failed, but in 1962, after a stint as a bankruptcy judge, he was appointed to the district court by President John F. Kennedy He earned a reputation as a pragmatic jurist whose middle-of-the-road rulings reflect a desire to apply rather than make the law.

Judge Brown is still working, probably because he loves his job (or is totally dedicated to it).

The Constitution grants federal judges an almost-unparalleled option to keep working “during good behavior,” which, in practice, has meant as long as they want. But since that language was written, average life expectancy has more than doubled, to almost 80, and the number of people who live beyond 100 is rapidly growing. (Of the 10 oldest practicing federal judges on record, all but one served in the last 15 years.)

You can thank Judge Brown for this gem of a quote:

“At this age, I’m not even buying green bananas.”

3) “Why Exercise Won’t Make You Thin” [The Guardian] – perhaps a heretical perspective on trying to lose weight, but worth highlighting:

Most of us have a grasp of the rudiments of weight gain and loss: you put energy (calories) into your body through food, you expend them through movement, and any that don’t get burned off are stored in your body as fat. Unfortunately, the maths isn’t in our favour. “In theory, of course, it’s possible that you can burn more calories than you eat,” says Dr Susan Jebb, head of nutrition and health research at the Medical Research Council and one of the government’s go-to academics for advice on nutrition. “But you have to do an awful lot more exercise than most people realise. To burn off an extra 500 calories is typically an extra two hours of cycling. And that’s about two doughnuts.”

While the article is UK-centric, it’s worth reading. Are we confusing cause and effect in the relationship among dieting, exercise, and weight loss?