This Is What Happens to Your Brain on a Diet
An expert explains how our brains inhibit weight loss—and why diets just don't work.
Photo: lucapierro - Getty
It seems like losing weight should be as simple as watching what you eat and engaging in regular exercise-but many of us aren't so lucky. Not only can losing weight be difficult, but maintaining that weight loss can feel even harder. We spoke with Sandra Aamodt, Ph.D., a neuroscientist, writer and author of Why Diets Make Us Fat, on the crucial role our brains play when it comes to our weight.
According to Aamodt, losing weight-especially a large amount-is often so difficult because our brains weren't wired to live in a state of weight loss. The need to lose 10 percent or more of one's body weight is a relatively new concept in modern civilization, as those in first-world countries are living in such an extreme food surplus that would have been unfathomable to others before us.
"Being too heavy hasn't historically been a threat to survival until about 50 years ago," Aamodt said. "It was just harder to achieve a high weight back then because there wasn't much food available. Your body was more focused on preventing starvation."
Our brains simply just don't know how to function in a society with convenience stores and fast food joints at every corner, supermarkets full of just about any food one could imagine, and kitchens always stocked with our favorite foods. Most societies before us survived solely on what they could grow, hunt or forage for instead of being able to give in to a craving virtually whenever they wanted, like us.
Our Brain Has Its Own Ideal Weight for Us
Aamodt said it's just too easy to not pay attention to what you're eating-or how much-especially in our busy, stressful lives. Stress and frequently eating while distracted by our phone or the TV (guilty!) can lead to overeating or an increased consumption of unhealthy foods.
These and other factors-like sedentary lifestyles-can cause our weight to slowly creep up without us knowing, and our brains adjust accordingly. This new, higher weight now becomes your brain's "ideal weight" and your body will seek to maintain it. Once we finally realize our pants don't fit quite like they used to or the number on the scale surprises us, Aamodt says, we often tend to freak out, decide to go on a diet, and our brains just can't follow suit. Your brain thinks your body is starving and lowers your metabolism to conserve energy, or will even increase your appetite in pursuit of maintenance (learn more about what happens to your metabolism when you lose weight).
This maintenance weight the brain establishes for the body was once called the "set point weight," but now Aamodt and her colleagues prefer the term "defended range," as your brain typically has a 10- to 15-pound swing that it's comfortable with your body living in. Unfortunately for some, this may mean your body is incapable of thriving in your own desired weight range and even if you reach it, your brain will always fight to get back to where it thinks you should be.
An Obsession with "Skinny"
Aamodt says one of the major issues for those struggling with their weight is the unrealistic standards society sets for us. And sadly, this keeps many people from achieving true and lasting health.
"We've all been brainwashed into thinking we need to be painfully thin to be healthy," Aamodt said. "Even many doctors overestimate how much weight one needs to lose."
While morbid obesity is one thing, Aamodt says being overweight is not really so much of a medical problem as it is a cultural and aesthetic problem. She said doctors often wrongfully put patients on an intense weight-loss regimen to get into this "desired" range, which may not actually be achievable.
Aamodt says you can take two people at the same height and weight, and they could have vastly different mechanisms for maintaining it. One might have to consume 600-800 fewer calories each day for maintenance if she's not at a weight within her defended range. Aamodt says that while most people tend to think our bodies function the same, that just isn't true.
Why Diets Don't Work
While it is certainly possible to achieve a "goal weight" (and many people do), Aamodt says to do so with caution and to listen to your body every step of the way. She says there are really only two ways to go about losing weight and keeping it off: deciding that you're willing to feel restricted and hungry (constantly employing your willpower and realistically not being very happy or satisfied)-or you can focus on overall health instead of a number.
This is because while your brain can eventually adjust to a new, lower weight while dieting, it will likely need you to continue those same dieting behaviors to maintain it. This is extremely concerning for those following restricted diets, as they are not meant to be followed long-term-which is why so many people gain all the weight back and even experience poorer health as a consequence.
How to Break the Dieting Cycle
Aamodt herself wrestled with yo-yo dieting for decades-ranging between 10- and 40-pound losses and gains. At age 42, she finally decided to spend a year in a non-diet experiment, concerning herself more with listening to her hunger cues and practicing mindful eating instead of focusing on what she can and cannot eat.
Aamodt says while it can be scary to give up dieting for fear one will lose all self-control, she said bingeing on foods is likely a result of dieting rather than our personalities. When people practice mindful or intuitive eating, most end up consuming less than they feared (learn more about intuitive eating and how to get started).
Aamodt says that by focusing on exercise, eating those veggies and reducing stress (dieting being one of those big stresses), your body will naturally find its "defended range," and you can end up at the weight that is a match for your biological characteristics and natural behaviors instead of being a result of enslavement to a diet. Eating when hungry and stopping when full for approximately six months will make a huge difference in helping you achieve a safe weight for you specifically.
"Let your body settle where it wants to settle," Aamodt says. "The major payoffs come later as you relax into the idea that you don't need to feel guilty for everything. It's OK to eat the pizza!"
It's easy to associate a certain weight with prime health-or even poor health-and while most people do this, Aamodt says a number on a scale isn't always an accurate representation of health. Striving for a certain amount of weight loss or seeking to maintain a weight our body just isn't comfortable at can cause our health to deteriorate and send us into a vicious binge-dieting cycle.
Aamodt says she bets that we all have a pretty good idea of what our personal "defended range" is, as it's the place on the weight chart our body tends to go back to. Listening to our bodies instead of to the dieting tips of celebrities, social media influencers or even well-meaning friends is the best way to achieve optimal health and finally become comfortable in our own skin.