At any given time, about half of all Americans are trying to lose weight — and we can assume it will be even more than that once everyone emerges from our collective bread-and-cookie-insulated quarantine cocoon. That means millions of people are doing keto, paleo, intermittent fasting, Optavia, Atkins and all the other diets that limit what, when and how you eat. And as you can tell from all those “before and after” Instagram shots, many dieters do lose weight — at least at first. But for the vast majority — some 98% — it inevitably comes back, leading to a national reckoning of guilt, disappointment and the biggest question of all: What am I doing wrong? Why can’t I keep off the weight?
Here’s the truth: It’s not you. It’s biology.
The dirty little secret of the dieting industry is that most diets are destined to fail. But we are still bombarded with the message that if we only find the right diet we will be thin — which has been conflated with "beautiful" in our culture — and all our troubles will melt away along with our love handles. “The diet industry is a $72 billion dollar business, so there's an extraordinary amount of money that’s hooked into selling the idea that there is something wrong with us, and if only we buy their product, we can find salvation,” says Lindo Bacon, PhD, associate nutritionist at UC-Davis and author of Health at Every Size: The Surprising Truth About Your Weight. But according to one well known study at UCLA, not only do most people eventually gain back the weight they lost on diets, but as many as two-thirds may wind up gaining back more.
That type of “failure” can take a huge emotional toll, says Alissa Rumsey, RD, a certified intuitive eating counselor and the author of the upcoming book Unapologetic Eating: Make Peace with Food and Transform Your Life. “People who have dieted have been led to think that if you can’t lose weight, it's your fault and it's all about willpower — and there’s a lot of shame around that. But in reality, it has nothing to do with willpower.”
What really happens to your body on a diet
At first, it’s simple math — as you decrease the number of calories you’re consuming (whether by counting points, eliminating categories of food, or restricting the hours when you can eat) you will certainly lose weight. But then your body and your brain catch on, and they try to stop the process. In essence, your body thinks you’re starving and it's trying to save you, protecting you at all costs.
This is largely thanks to the hormone leptin, which is produced in fat cells, explains Dr. Caroline Apovian, professor of medicine and pediatrics and director of the Nutrition and Weight Management Center at Boston University Medical Center. “One of the main functions of leptin is to protect your fat stores, because you need fat to make sure that you have an energy source in case there’s no food available,” she explains. Leptin is what tells your brain you’re full — as you reduce the amount of fat in your body, you produce less of it, so you don’t get that same sense of satiety you once did after dinner or a midday snack. Instead, your body starts receiving hormonal messages saying, “All hands on deck! We have to get this person to gain weight!”
One of the ways it does this is to send a message to your thyroid to slow down your resting metabolism rate (RMR) — the number of calories your body burns to keep you breathing and digesting. If you typically burn a certain number of calories a day at rest, your RMR may slow down to burning a few hundred fewer a day, as your body adjusts to hold on to as much energy as possible to use later. In fact, one headline-making study that followed contestants from The Biggest Loser six years after they appeared on the weight-loss show found that most had not only regained the weight and body fat they had lost, but their RMR had dropped from an average of 2,607 calories per day before the show to 1,900 calories a day six years later. The contestants’ slowed metabolisms may not have been the only reason they regained the weight, but it is true that the more you diet, the fewer calories you burn, meaning you have to restrict your diet even more to keep losing weight, or even to maintain your current weight.
Your happy weight
This life-preserving system is called “defense of body weight,” and its goal is to keep you within a 10 to 20 pound range, or your “set point” weight. Bacon describes the set-point system as similar to a thermostat, with your body constantly making adjustments to stay at the same weight. “There’s a certain fat level that your body wants to maintain, and when you drop below that range, your body's going to put all kinds of mechanisms into place to try to get you back in a healthy range,” Bacon says. “At first it will try to elicit your help, by making you feel hungry [that’s thanks to hormones such as ghrelin]. But if that doesn’t work, it can get more aggressive, by slowing down your metabolism.”
But wait, there’s more: Not only do you get the double whammy of feeling hungrier and having a slower metabolism, but the types of food you crave may change, too. “When you lose body fat because you're dieting, your hunger center is triggered, and that includes the rewards center, which makes you crave sweets because that’s the easiest way to get a lot of calories,” says Dr. Apovian. You might even get cravings for foods you would normally walk right by without a second thought, Bacon adds: “You're willing to eat anything because your body's trying to just get you the calories that it wants to restore.”
Losing touch with your own hunger
Another side effect of dieting: When you pay attention only to external rules of what and when to eat — and how guilty you should feel if you eat the “wrong” thing — you can become disconnected from the cues from your own body, says Rumsey, who points out that researchers have seen some of the same behaviors — such as binge-eating and bulimia — in people who are dieting and in people who are dealing with a true scarcity of food. “We get disconnected from our feelings of hunger, fullness, and satisfaction. And we also lose that sense of food as being something we enjoy, that feels good in our body,” Rumsey says.
But what about all those people losing weight and keeping it off?
Attention, anyone who is reading this article and saying, But what about Rebel Wilson, Adele or Jennifer Hudson? How did that guy Matt from college drop 50 pounds and keep it off for years?: For more than 20 years, the National Weight Control Study has tracked more than 10,000 people in the 2% who have beaten the odds and maintained a weight loss of more than 30 pounds for at least five years, and it found that they do it with constant vigilance, says Dr. Apovian.
But obsessing about your weight every day and considering what you eat every meal is a huge commitment — and for many people, it's just not a realistic (or desirable) way to spend your mental energy or time, especially if you're working full-time or juggling family care. What happens when you go on vacation, get too busy to cook or are stuck at home during a pandemic? The fear and guilt from slipping just once or twice can throw your entire regimen off, leading to renewed resolutions to be stricter with yourself. It's a setup for more guilt, more vigilance and more all-too-human "slipping up." Wash, rinse, repeat.
So what can I do to be healthy?
But when you start to look at health and well-being as separate from the numbers on a scale (and yes, you can be perfectly healthy without being thin), a whole new way of living comes into focus. “It’s about food and nutrition, but also movement and stress management and coping skills — all those things coming from a place of self-care,” Rumsey says. “It’s making decisions about what to eat not from a negative place of restriction and control, but from a place of taking care of yourself. It’s about coming back into your own body and figuring out what that looks like for you.” Through the practice of intuitive eating, you replace an external set of dietary rules with the wisdom of your body. "You learn to pay attention to the physical sensations that arise in your body and let those cues guide you,” Rumsey explains.
You can also find some kind of exercise that brings you joy — whether that means long, meditative walks, Zoom dance classes or playing softball every weekend with your friends—since movement is crucial not only for brain and heart health, but keeps your metabolism humming along.
What do you get from saying good-bye to commercialized restrictive diets and respecting your body, in whatever beautiful, healthy shape it comes in? "There is a real sense of freedom that comes from not thinking about food all the time, not feeling guilty, and being able to just eat a meal and move on," says Rumsey. "I've had clients say, 'I have to find a new hobby — I have so much extra time in my day from not obsessing about food!'"