Junkfood Science: How we’ve come to believe that overeating causes obesity

February 07, 2008

How we’ve come to believe that overeating causes obesity

The bipartisan Mississippi legislation, which proposed to ban restaurants from serving fat people purportedly to help them lose weight, has highlighted the most popular misconception about fat people. One that even a lot of fat people have been led to believe: that they overeat and that’s why they’re obese.

This concept has been drilled into us and “everybody knows” it to be true. But is it? Suppose we’ve been convinced of this by the continuation of a fundamental misinterpretation of anecdotal evidence and certain studies — suggesting that a correlation between overeating and some obese people means that overeating causes obesity. You’re about to learn that this common fallacy of logic is precisely what has misled conventional wisdom to believe something that isn’t true — when, in fact, the science and far sounder clinical research for more than half a century has disproven it.

In a cruel twist, it is the solution to this belief that has created the very perception of “overeating” popularly pinned on fat people.

This goes beyond the fact that the mere act of eating just like anyone else is labeled as "overeating" in a fat person. But people, regardless of their size, who believe they have “overeating” issues are most often exhibiting completely normal, natural biological responses to starvation, hunger and weight loss — in developed countries, that means voluntary starvation, otherwise called dieting. Healthy people, whether naturally fat or thin, who aren’t dieting or trying to control their weights don't have problems with “overeating."

The biological reality of our weights and weight control, and the effects of dieting, were clinically demonstrated more than 50 years ago in what remains the definitive research on the subject. The findings in this famous study, revolutionary at the time, have been replicated in the most precise, complicated metabolic studies of food intake behavior, energy expenditure and the biochemistry of fat conducted by the country’s top obesity researchers.

This classic study made the most important contributions to our understanding of dieting, yet surprisingly few consumers today have ever heard of it. It was led by one of the world’s most renowned scientists, Ancel Benjamin Keys, Ph.D., popularly known for inventing K-rations — those indestructible transportable foodstuffs of white crackers, greasy sausage, chocolate and candy — that kept our soldiers alive during World War II.

In the 1940s, when starvation was widespread throughout war-torn Europe, little was known about the effects of human starvation or how to best refeed people who’d suffered from such deprivations. Dr. Keys led the first scientific study of calorie restrictions, at the Laboratory of Physiological Hygiene at the University of Minnesota, for the War Department. The researchers wanted to understand the medical needs facing millions of starving war victims and how best to renourish and rehabilitate them to health after the war. Their study was known as the Minnesota Starvation Study and the results were published in the legendary two-volume, Biology of Human Starvation (Minneapolis: University of Minneapolis, 1950).

The study itself was so comprehensive and intense, however, that even Dr. Keys admitted no other human experiment quite like it will ever be done again because, given what we now know, it would be seen as too cruel and life-threatening. While the degree of suffering the participants underwent would violate what is seen as the ethical rights for human research subjects today, in one respect this study was different from obesity and weight loss research done today. These men were not volunteering because they felt they needed to lose weight for fear that their own lives were endangered, nor were the study authors motivated by personal gain or selling a weight loss program.

Even the recruitment poster for the Minnesota Experiment, dated May 27, 1944, asked for men willing to starve so others may be better fed. The volunteers were all conscientious objectors to the war who said they wanted to do something of real meaning for their country, make a contribution to science and help to improve the medical care for the millions of starving people in Europe. They gave their consent freely, without a feeling of personal duress and with full knowledge of the risks. The recruitment information they were given stressed how difficult the experiment would be. One participant later said: “They explained what was going to happen. There was nothing held back. They explained that they could not assure me that there would be no permanent damage... They did not know what would happen. This is what they were trying to find out... really they emphasized the discomfort... this was not going to be an easy task down the road.”

Sixty years later, Johns Hopkins interviewed the surviving study participants for their first-hand experiences and they all said they would do it again:

[T]he men continued to look back on participation in the Minnesota Experiment as one of the most important and memorable activities in their lives. Wesley Miller reported, “It’s colored my whole life experience... [and was] one of the most important things I ever did... I’m proud of the work the Civilian Public Service did during the war." Samuel Legg seemed to speak for all of the men when he commented, “I think probably most of us are feeling we did something good and are glad we did it, and that helps us live a better life."

The experiment — the starvation syndrome

The 40 young male participants were carefully selected among hundreds of volunteers for being especially psychologically and socially well-adjusted, good-humored, motivated, well-educated, active and healthy. They were put on calorie-restrictive diets of about 1,600 calorie/day, meant to reflect that experienced in war-torn regions, for 3 months. They dieted to lose 2.5 pounds a week to lose 25% of their natural body weight. The calories were more generous than many weight loss diets prescribe today!

What this study was actually studying, of course, was dieting and restrictive eating — our bodies can’t tell the difference if they’re being semi-starved involuntarily like war victims or voluntarily. During the 3-month nutritional rehabilitation period after the diet, the men were randomly assigned to various nutritional regimens, with differing levels of calories, proteins and vitamins. The men lived at the lab and everything they ate and did was closely monitored, as was their health with a battery of tests. Daily exercise was walking about 3 miles a day.

As difficult as the diets were for the subjects, they knew their hunger was less than that of the war victims they were trying to help. All but four completed the study. One of the participants said: “The difference between us and the people we were trying to serve: they probably had less food than we did. We were starving under the best possible medical conditions. And most of all, we knew the exact day on which our torture was going to end. None of that was true of people in Belgium, the Netherlands, or whatever.”

Dr. Keys and colleagues painstakingly chronicled how the men did during the 6 months of dietary interventions and for up to a year afterwards. This study scientifically defined for the first time “the starvation syndrome.”

As the men lost weight, their physical endurance dropped by half, their strength about 10%, and their reflexes became sluggish — with the men initially the most fit showing the greatest deterioration, according to Dr. Keys. The men’s resting metabolic rates declined by 40%, their heart volume shrank about 20%, their pulses slowed and their body temperatures dropped. They complained of feeling cold, tired and hungry; having trouble concentrating; of impaired judgment and comprehension; dizzy spells; visual disturbances; ringing in their ears; tingling and numbing of their extremities; stomach aches, body aches and headaches; trouble sleeping; hair thinning; and their skin growing dry and thin. Their sexual function and testes size were reduced and they lost all interest in sex. They had every physical indication of accelerated aging.

As the physical effects became more dramatic, one study participant said Mrs. Keys confided that Dr. Keys “went through terrible times during the experiment as we lost weight and became gaunt and so on. And he would come home and say, ‘What am I doing to these young men? I had no idea it was going to be this hard.’”

But the psychological changes that were brought on by dieting, even among these robust men with only moderate calorie restrictions, were the most profound and unexpected. So much so that Dr. Keys called it “semistarvation neurosis.” The men became nervous, anxious, apathetic, withdrawn, impatient, self-critical with distorted body images and even feeling overweight, moody, emotional and depressed. A few even mutilated themselves, one chopping off three fingers in stress. They lost their ambition and feelings of adequacy, and their cultural and academic interests narrowed. They neglected their appearance, became loners and their social and family relationships suffered. They lost their senses of humor, love and compassion. Instead, they became obsessed with food, thinking, talking and reading about it constantly; developed weird eating rituals; began hoarding things; consumed vast amounts of coffee and tea; and chewed gum incessantly (as many as 40 packages a day). Binge eating episodes also became a problem as some of the men were unable to continue to restrict their eating in their hunger.

The act of restricting food and the constant hunger “made food the most important thing in one’s life,” said one of the participants. “Food became the one central and only thing really in one’s life. And life is pretty dull if that’s the only thing. I mean, if you went to a movie, you weren’t particularly interested in the love scenes, but you noticed every time they ate and what they ate.”

These experiences are familiar to those who’ve spent their lives dieting. In fact, many of the symptoms once thought to be primary features of anorexia nervosa are actually normal biological responses of undernutrition and restrictive eating, said David M. Garner, PhD., director of River Centre Clinic in Sylvania, Ohio, in Psychoeducational principles in the treatment of eating disorders (NY: Guilford Press, 1997). It was actually Dr. Keys’ research that first evidenced the role of dieting in increasing risks for eating disorders.

The extreme physical and mental effects Dr. Keys observed led to his famous quote: “Starved people cannot be taught democracy. To talk about the will of the people when you aren’t feeding them is perfect hogwash.” This was also what led early feminist activists to see dieting and weight concerns as a way to keep women preoccupied with food, filled with guilt and self-hatred, more easily influenced by others, and too mentally and physically exhausted to succeed professionally and politically.

The aftermath

The last part of the Minnesota Starvation Study revealed perhaps the most important effects. When the men were allowed to eat ad libitum again, they had insatiable appetites, yet never felt full. Even five months later, some continued to have dysfunctional eating, although most were finally regaining some normalization of their eating. As they regained their weights, their suppressed metabolism and energy levels returned, although even three months after ending the diet none of the men had yet regained their former physical capacity, noted Dr. Keys.

While it seemed the men were “overeating,” Dr. Keys discovered that their bodies actually needed inordinate amount of calories for their tissues to be rebuilt:

Our experiments have shown that in an adult man no appreciable rehabilitation can take place on a diet of 2,000 calories a day. The proper level is more like 4,000 kcal daily for some months. The character of the rehabilitation diet is important also, but unless calories are abundant, then extra proteins, vitamins and minerals are of little value.

In other words, they weren’t really “overeating,” it was a biological, normal effect of hunger and weight loss. The men regained their original weights plus 10%. The regained weight was disproportionally fat, and their lean body mass recovered much more slowly. With unlimited food and unrestricted eating, their weights plateaued and finally, about 9 months later, most had naturally returned to their initial weights without trying — giving scientists one of the first demonstrations that each body has a natural, genetic set point, whether it be fat or thin. Despite the fear that with unrestrained eating everyone would continue to grow larger, it isn't true.

As Dr. Garner explained:

One of the most notable implications of the Minnesota experiment is that it challenges the popular notion that body weight is easily altered if one simply exercises a bit of “willpower." It also demonstrates that the body is not simply “reprogrammed" at a lower set point once weight loss has been achieved. The volunteers' experimental diet was unsuccessful in overriding their bodies' strong propensity to defend a particular weight level. Again, it is important to emphasize that following the months of refeeding, the Minnesota volunteers did not skyrocket into obesity.

The Minnesota Starvation Study also demonstrated that “overeating” and starvation-induced hunger only remained evident as long as weight was below what was natural for each person. It is very rarely seen when people aren’t dieting and they allow themselves to eat naturally and their bodies to be whatever they are genetically meant to be. In fact, healthy fat people actually eat no differently than a naturally thin person; they maintain a stable weight and energy balance just like a naturally thin person, just at a different set point range.

When obese people are at the size genetically normal for them, their energy balance and requirements per unit of lean body mass are indistinguishable from you or me or any other ‘normal’ weight individual, said Dr. Rudolph L. Leibel, M.D., now at Columbia University, whose laboratory at Rockefeller University, New York, has conducted some of the most detailed, complex metabolic research on energy balance and the biochemistry of fat. “An obese person is metabolically just like a lean person, except they’re bigger,” he said.

Scientists at Rockefeller University replicated the findings of the Minnesota Starvation study and went on to learn that the body has an incredibly complex and sophisticated system to regulate its fat stores. And when those fat levels deviate from the body’s genetic setpoint, compensatory mechanisms kick in to return the body to is normal state without us having a lot of say about the matter.

Decades of sound studies have continued to show that healthy obese people eat and behave no differently than anyone else to explain why their bodies are bigger. It’s not “overeating,” or eating “unhealthy” foods or not enough “healthy” foods, or too little activity, that explains why some of us are fat and others lean.

Conventional wisdom on obesity’s cause hasn’t changed appreciably from the time of Galen, who held obese individuals responsible for their size, said obesity researcher Dr. Jeffrey M. Friedman, M.D., Ph.D., head of the Laboratory of Molecular Genetics at Rockefeller University. The commonly held belief that obese people can simply decide to eat less and exercise more to control their weight is “at odds with substantial scientific evidence illuminating a precise and powerful biological system that maintains body weight within a relatively narrow range (10-20 pounds),” he said. Fat people are victimized by a social stigma predicated on these myths, he wrote in a 2004 issue of Nature Medicine. Our body shapes and sizes are, to a most significant extent, genetically determined. “The heritability of obesity is equivalent to that of height and greater than that of almost every other condition that has been studied,” said Dr. Friedman. Someone genetically predisposed to obesity will become obese independent of their caloric intake, he explains. And, while it may explain a few extra pounds, it’s not the environment, where almost everyone as unlimited access to calories, that explains the marked difference in body weights in our population today.

"Why has the scientific evidence from long-standing obesity research not found its way into the minds of the public and even a significant proportion of the scientific community?," asks Dr. Friedman. “Perhaps," he says, "it is because these views are shaped by a constant barrage of advertisements from the diet industry which has a multibillion dollar interest in promoting the view that weight can be controlled through volition alone... Perhaps it is because humans prefer to believe that the conscious wish to be trim is an element of our “free will” and should therefore dominate” our genes. But the average person eats one million or more calories each year, while weight changes very little, because energy balance is biologically regulated with a precision of greater than 99.5%, which far exceeds what can be consciously controlled, he explained.

But if you’re a diet doctor or government bureaucrat and wanted to “prove” that fat people overeat and thus “needed” your weight loss program or your ‘healthy’ eating interventions, who would you study and compare to a slender person? Fat people who were comfortable with their bodies and eating normally... or fat people concerned about their weights and dieting?

In the years following this classic study, Dr. Keys put no stock in weight loss diets or height-and-weight charts. He called those charts “arm-chair concoctions starting with questionable assumptions and ending with three sets of standards for 'body frames' which were never measured or even properly defined.” And “diet fads are for the birds, if you don’t like birds,” he said in a 1979 University of Minnesota Update. He also noted diets such as those promoted by Adele Davis, based on natural foods and fears about processed foods, are “just full of hogwash.” There’s “no great sense to them at all.”

This past week while the country went into a furor over that discriminatory legislation targeting obese people — and countless interests proposed their own solutions for eradicating obesity, from banning all-you-can eat buffets, fast food or sodas; to mandating vegan or macrobiotic diets or compulsory exercise; to more funding for diets or bariatric surgeries — very few people got just how scientifically insupportable any of it really was.

© 2008 Sandy Szwarc. All rights reserved.

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