Note: This story first appeared in The 2-Percent Newsletter. I publish stories like this weekly, and most don’t make it onto my website. Sign up here to not miss future stories.
A few weeks ago I wrote about one of the most dangerous studies of all time and how it can tell us everything we need to know about weight loss.
In that study, which occurred at the height of World War II, 36 men entered a lab to starve. The scientists wanted to understand the effects of starvation so they could help starving people in war-torn Europe.
Many readers asked me what happened to the men after the study. It’s a great question.
The scientists began refeeding the men to return them to a healthy weight. What happened next and in the years after reveal the consequential long-term effects that weight loss can have on our bodies and minds.
This is what happens once we’ve lost weight — and even after we’ve regained it:
We’re more likely to binge eat
Before the experiment, the men said they rarely overate and never binge ate. This all changed during the refeeding. The men consumed an average of 11,000 calories on the days they were allowed to eat anything they wanted. That’s equal to 20 Big Macs.
More than 30 percent of the men admitted to binge eating (defined as not being able to control oneself from eating large amounts of food in a short period). Ten percent admitted to binge eating enough that they threw up. One man ate so much that he had to go to the hospital for extreme gastric distention.
The idea that significant weight loss can lead to binge eating has played out in other examples. Canadian WWII vets held captive in German POW camps reported more binge eating than other vets. The more weight those POWs lost in the camps, the more often they binged later in life.
What we learned: After we lose a significant amount of weight, our brain responds by sending out mega cravings for calorie-dense items. Meanwhile, it also reduces the hormones that signal fulness. It’s a defense mechanism that compels us to overeat and regain the lost weight.
This phenomenon also plays out in smaller ways: A team at the NIH recently found that for every 2 pounds a person loses, their brain unconsciously ramps up their hunger and causes them to eat about 100 more calories a day.
We often regain more than we lost
The subjects had an average body mass index (a ratio of our height to our weight, also known as BMI) of 22 before the study. That number equates to, for example, a six-foot-tall person weighing 160 pounds. At the low point of the starvation period, the men dropped down to a BMI of about 16. That’s equal to our six-foot-tall example weighing 120 pounds.
But seven months into the refeeding process, the participants had rebounded up to a BMI of 24, or close to 175 pounds for our six-footer. One participant jumped 50 pounds above his starting weight.
It took the participants an average of about 13 months to lose that rebound weight and return to their pre-study weight. Some participants took more than four years to return to their starting weights.
What we learned: Research shows that dieters who lose weight often regain and end up heavier than their starting point. This is because our body pulls various physical and psychological tricks to bulk us back up. For example, it alters our metabolism, hunger hormones, and activity levels.
Think of this physiological response like lifting a weight. Weightlifting signals your body to build more muscle so the weight is easier to lift next time. Similarly, weight loss signals your body to try to gain more weight so it has more reserves to keep you alive for the next period of weight loss.
We still obsess over food
Recall that during the starvation period the men became obsessed with food. Food haunted their thoughts and dreams and took over their conversations.
But many of them remained preoccupied with food even after they gained back the weight. Some said that their perspectives and perceptions of food were forever changed. They faced more intense hunger more frequently than they did before the study. One described himself as, “being hungry and eating almost continuously for years after.”
What we learned: Our brain remembers “famine,” whether from a diet or a real famine. Once we’ve lost weight — and even if we’ve regained it — the brain puts more focus on food so we’re more likely to eat and be better prepared for the next famine.
We see this play out in the real world. Think of, for example, a grandparent who grew up during the Great Depression. That generation taught their children to “finish your plate,” and hates food waste. (A similar phenomenon may happen with our generation — the Covid-19 pandemic may lead to lasting memories of empty grocery store shelves and compel us to keep more food, hand sanitizer, and toilet paper in storage.)
We can pick up body image issues
The men didn’t fret about their appearance before the experiment. But many developed body-image issues during the regain period. They worried that they’d put on fat in their stomach and butt. Some said they didn’t like how “fat” they felt as they worked their way from emaciation to a healthy weight. Others began commenting that many normal-weight people looked overweight.
What we learned: Some people suffer from impaired body image issues after weight loss. This didn’t happen to all the participants, and it of course doesn’t happen to all people who lose weight. But the study results do suggest that weight loss can bring about body image issues in some susceptible people. This is why people with anorexia often describe themselves as fat even when they are unhealthily thin.
We can form a food-happiness habit loop
Most of the men became severely depressed during the starvation period. One, for example, cut off three of his fingers and reported to the scientists that he wasn’t sure if he did it on purpose.
The study’s refeeding phase quickly solved this problem. The scientists discovered a clear correlation between calories and psychological wellbeing. The men in the group who were refed the fastest were the happiest while those who were refed the slowest remained the most depressed for the longest.
What we learned: As we lose weight, our body reacts by making us feel discontent and depressed. When we eat more, we feel happier. This incentivizes us to … eat more. And this can sabotage our weight loss in the short term — and long-term. It can build a habit loop where our brain associates food with happiness, which can potentially lead to behaviors like stress-eating.
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As I wrote in the original piece, the great irony is that these mechanisms were once beneficial. During the crucible of evolution, they helped us save energy, focus on food, and prepare for the next famine.
But we now have easy access to calorie-dense food and live in no-effort environments. These tricks now backfire and explain why 72 percent of Americans are overweight and why losing weight can be such a roller coaster. Today our bodies have no clue whether our weight loss was caused by, say, a fad diet we decided to try or a dangerous famine we were forced into. Evolution wired us to act as if all weight loss is a threat to our safety, so it fires on sneaky machinery that helps us regain and even bulk up for the next famine.
I can identify, in a smaller way, what these men went through. If you read the last story, you’ll know that I became interested in this topic after spending a month in the Alaskan wilderness. Due to weight constraints, we packed in roughly 2,000 calories a day. But we burned far more than that, thanks to carrying 90-pound packs across rough terrain all day. I returned home 10 pounds lighter. My first meal back was at an all-you-can-eat sushi joint. The restaurant definitely lost money on me that night.
And so, after returning from the wild, I traveled to meet a person who could help me understand this topic. He’s a 20-something who has an IQ of 160 and got his Ph.D. at just 23 years old. He’s developed methods that help people in the modern world face the harsh and lasting realities of weight loss. He’s built a tribe of three-percenters, the tiny fraction of people who manage to lose weight and keep it off. His methods leverage our evolutionary adaptations and unconscious biases rather than fighting against them. “Losing weight is easy,” he told me. “It’s keeping it off that’s hard. That’s where I come in.”
He’s just one of the people I embedded myself with as I wrote my book, The Comfort Crisis.
