Can Hunger Change Your Brain? Ancel Keys and the Danger of Dieting
In 1944, at the tail end of World War II, the world’s leading nutritionist, Ancel Keys, put out a call for study participants. Famine was widespread in occupied Europe, and Keys wanted to understand the physical effects of malnutrition. He was particularly interested in how to re-feed those who were starving.
Over 400 men applied, and 36 conscientious objectors (men who chose not to fight in the war based on moral grounds) joined the cause.
Recruitment poster, May 1944
The experiment spanned the length of a year and consisted of three distinct phases.
For the first three months, the men’s diet was monitored to get them to their optimum base weight—they were allowed to eat what they wanted. This was followed by a six month period of semi-starvation, during which the men’s caloric intake was reduced so as to bring them to the edge of starvation. And the final three months consisted of re-feeding in which the men’s calorie intake was slowly and methodically increased to measure changes in health and mood.
They stopped laughing. They became obsessed with food. They pored over cookbooks and stayed up late into the night studying recipes.
Deprivation in the second phase had immediate and marked health results. The men’s heart rates slowed, their hearts actually shrank in size, and their blood volume dropped. Their faces sank, their ribs protruded, and their ankles and legs swelled as a result of edema (excess fluid in the tissues).
But perhaps more interestingly were the psychological effects. The men retreated into themselves as apathy took hold. They lost interest in politics, world events, sex, and romance. They stopped laughing. They became obsessed with food. They pored over cookbooks and stayed up late into the night studying recipes. They created elaborate rituals around mealtime and grew irate if they had to wait too long to eat. Scraps of food were scavenged from garbage cans. One man purchased donuts from a bakeshop and handed them out to children. He then stood there and watched as they ate them. Another participant began dreaming of cannibalism and was quickly dismissed from the study after threatening to kill Keys and himself.
Keys described the participants as “men who postponed their living, while they endured the awful present.”
Only 32 of the 36 men completed the semi-starvation phase.
Years later, looking back on the experience, one participant said, “I don’t know many other things in my life that I looked forward to being over with any more than this experiment. And it wasn’t so much…because of the physical discomfort, but because it made food the most important thing in one’s life. And life is pretty dull if that’s the only thing.”
Many of the men found the re-feeding phase the most difficult. When food was reintroduced (or, more food, I should say) it was done slowly. Two hundred calories, then 400, 600, 800. Keys was able to determine that in order for the muscles to recover, the approximate daily intake needed to be, at minimum, 4,000 calories. Despite the increase in calories, the men fought against a gnawing, persistent sense of hunger. They’d later describe it as a feeling that no amount of food could satiate. And so Keys took all restrictions off. Left to their own devices the men ate between 5,000 and 11,500 calories per day.
When I tell this story, this is always the point I pause to ask, How many calories do you think the men were eating? On the edge of starvation what was the calorie count?
1,000? 500? 800, maybe?
1,600. 1,567 to be exact.
When I was nineteen years old I dieted for ten weeks. I followed a plan recommended by both my pediatrician and OB-GYN. For ten weeks I ate less than the number listed above. And I began to binge.
A friend once described binging as the body’s override system. Think about when a body faints—it’s often because the heart isn’t getting enough blood, and so the body makes it as easy as possible to move the blood—it overrides gravity. A binge is much like that—the body’s attempt to get as many calories into the body, as quickly as possible. Turns out evolution is a force and after thousands of years, is still primed for famine. And so a starving brain seeks out calories. I remember suddenly craving foods I’d never before loved—dense cakes and sugar-laden pastries. I ate and I ate and I ate. And then I retreated into myself.
Dieters are more likely than non-dieters to become obese.
Occasionally I’m still floored by the numbers. I dieted for 10 weeks and then lost six years of my life to an eating disorder—to a terrible cycle of restriction, binging, and weight gain. I always joke that it was a little science that saved my life. I laugh as I say it because it makes an incredibly dark chapter, less so, but it is nonetheless true.
Here is what the data says: After about five years, 41 percent of dieters gain back more weight than they lost. Weight loss, as a result of calorie restriction, results in a drastically slowed metabolism. Even as individuals regain weight, their metabolisms don’t catch up, and so they don’t burn as many calories as they should for someone their size. Dieters are more likely than non-dieters to become obese. Because the brain needs to ensure we eat, food actually tastes better to a starving body (the brain ups the pleasure hormones).
Calorie restriction over sustained periods of time has massive effects on physical and psychological well-being. And what’s really nuts is that we’ve had some idea of this since the 1940s.
But there’s more.
Sandra Aamodt, neuroscientist and author of Why Diets Make Us Fat: The Unintended Consequences of Our Obsession With Weight Loss wrote in The New York Times in 2016, “Our culture’s view of obesity as uniquely deadly is mistaken. Low fitness, smoking, high blood pressure, low income and loneliness are all better predictors of early death than obesity.” She then continued, “Obese people who exercise, eat enough vegetables and don’t smoke are no more likely to die young than normal-weight people with the same habits.”
It may very well be time for a radical shift in how we think about bodies. Anecdotal evidence, data, and available studies raise serious questions about our go-to narratives surrounding bodies, weight, and will-power. Perhaps diets, in their current form, simply don’t work. And perhaps it has something to do with the fact that our bodies have evolved over thousands of years to store fat in preparation for famine. Perhaps we need to stop talking about weight as though it is the ultimate indicator of a person’s health. Perhaps it’s time to throw out what we think we know, and try again.