3/4/2021 12:30:00 AM

Appetite with no off switch: How a function of our brains that helped keep our ancestors from starving could now be one of the biggest drivers of obesity.


Photo illustration: Sandra BrunerBrenda Goodman, MA                                         Medically reviewed byBrunilda Nazario, MDMarch, 3, 2021

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From the time her mom tucked her into bed at 8 o’clock each night, Angie Gibson would lie awake and listen for the click.It was the sound of her mother’s bedroom door finally latching shut as she turned in to sleep.Gibson, who says she was around age 6 at the time, knew that for 2 precious hours, until her father returned from his factory shift at 11:30 p.m., she could eat in secret.

She would slip out of her bed and begin scanning the fridge and cupboards for food that wouldn’t be easily missed. She knew the cream-filled Zingers snack cakes her dad liked were off-limits. But often they had enough hot dogs or slices of bologna that one or two wouldn’t be noticed.  headtopics.com

Gibson would microwave a frank and eat it on a piece of bread with mustard. Hillbilly hot dog, her family called it. Other times, she would savor slices of soft white bread dipped in ranch dressing.Gibson took care to stay hidden. She sometimes crouched in a corner of their tiny kitchen that couldn’t easily be seen from any of the doorways. 

Gibson’s parents worked factory jobs in North Carolina. They lived in a trailer and subsisted on a lot of cheap, processed food that they could afford on their minimum-wage salaries. “They like to talk about how they gave us Dr Pepper in our baby bottles and fed us honey buns when we were 6 months old and we turned out fine,” says Gibson, who is now 23.

Angie Gibson at her fourth grade chorus concert (left), when she was already 5 feet, 10 inches tall. At right is her sixth grade yearbook photo. By then, Gibson had grown an inch and weighed about 240 pounds.In many ways, Gibson turned out more than just fine. She’s the first in her family to graduate from college. She has a master’s degree in neuroscience. Today she’s a cancer researcher at the University of Alabama at Birmingham and is applying to medical schools.

At the same time, her childhood diet may have left a damaging imprint. All her life, she has been tormented by cravings for fatty, sugary foods and an urge to eat that feels beyond her control.Turns out, Gibson really is at the mercy of her own appetite. headtopics.com

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Eating With No Off SwitchThrough many millennia, the human body has retained a ferocious biological drive to eat and to hang on to calories.When you burn more calories than you’ve recently eaten, your body reacts by amping up your appetite while also delaying the message that you’re full. Specifically, it releases more hunger hormone ghrelin and less of the peptides that enable the gut to signal to the brain to quit eating.

This well-established concept is known as homeostasis.But researchers say Western convenience diets have exploited a different impulse to eat.While homeostasis is controlled by a cross-talk of hormones between the gut and the brain, this separate urge to eat is centered in the brain’s reward system, which is also involved in addictions. Experts call this “hedonic eating,” after Hedone, the Greek goddess of pleasure.

Hedonic appetite is stoked by the fatty, sugary, artificially enhanced foods that were a staple of Gibson's upbringing.“The obesity epidemic has nothing to do with the need for calories.”- Michael Lowe, PhD, professor of psychology at Drexel University

Eons ago, the first humans quickly learned that naturally sweet foods are never poisonous and therefore safe. Back then, these kinds of energy-dense foods were relatively rare. When early humans found one of these treats, the hedonic reward system encouraged them to keep eating. This kept our ancestors from starving. headtopics.com

But our hedonic appetites have turned on us. Hedonic eating is now being studied as one of the biggest drivers of obesity. That’s because modern society has become awash in easy-to-grab, highly processed foods that our pleasure-seeking brains compel us to eat.

Sweet foods, in particular, flood the brain with the chemical signal dopamine. Once triggered, people may seek them out over and over again for the jolt of pleasure they bring. Under this theory, a hankering for doughnuts could be as hard-wired as a craving for heroin or alcohol. Critically, just as our bodies don’t need addictive substances, they don’t need the extra calories in fried dough.

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“The obesity epidemic has nothing to do with the need for calories,” says Michael Lowe, PhD, a professor of psychology at Drexel University in Philadelphia. He coined the term “hedonic hunger,” or the primal drive to consume anything delectable even if we aren’t physically hungry.

Instead, Lowe says, “it has everything to do with wanting more food and, from my perspective, the pleasure from certain foods, and the calories are just along for the ride.”And those tasty triggers are everywhere. Ultra-processed foods such as soft drinks and fruit drinks, breads, breakfast cereals, chips, and frozen pizzas make up almost 60% of Americans’ daily calories. They’re an alchemy of sugar, salt, fats, artificial flavoring, color, and texture -- a precisely calibrated industrial recipe for temptation.

Once you pack on the pounds, any attempts to shed them usually backfire, says Kevin Hall, PhD, an expert on metabolism at the National Institutes of Health in Bethesda, MD. Hall calculates that about every 2-pound drop in weight ultimately saddles your waistline with a net hit of 130 more calories a day. Drop 10 pounds?  That’s 650 more calories a day your body will prompt you to eat.

Your body claws back the lost weight -- and then some -- via two routes at the same time. It slows your resting energy burn so you need fewer calories while it also ramps up hunger hormones and turns down hormones that make us feel full. The net result? You want to eat more than before you slimmed down.

Today’s humans are “completely unprepared to deal with” the consequences of this biological math, Lowe says. “Our bodies are primarily just like they were 10,000 years ago when we were living in nature.”While homeostatic hunger has a built-in cue to stop, hedonic eating is harder to control. With modern life nothing if not a buffet of high-calorie feasts, people like Angie Gibson must constantly wrestle with their runaway appetites.

“One of the things we have learned is that there often isn’t an off switch when we have more than we need, when we’re eating for pleasure,” Lowe says.The Link to Binge EatingBy 11th grade, Gibson says, she thinks she weighed 340 pounds, her all-time heaviest. At least that’s her guess. She stopped getting on the scale and simply bought clothes in bigger sizes. She got into a cycle of gorging and then starving herself.

But when Gibson arrived at the University of North Carolina at Wilmington, she gained a new lease on her health. The campus had free gyms and offered advice on nutrition. She biked to classes. Gibson’s weight dropped to 240 pounds -- her size in the sixth grade. She was thrilled.

Angie Gibson at 16 with her older brother, Jason Gibson Jr., in 2013 (left) and at her graduation from the University of North Carolina at Wilmington in 2019. Gibson reached her peak weight of 340 pounds as a high school junior. She credits counseling and a prescription she received in college with helping her to gain more control of her weight.

Yet college brought new stresses, too. After Gibson tangled with problems with her financial aid, she started gorging and restricting again. She often visited Cook Out, her favorite local fast-food chain, and ordered two of its signature trays. Each came with a hot dog, a corn dog, and a tortilla bacon wrap, plus a large soda. Gibson would devour it all in 20 minutes.

All that food made her sick. But she still craved more. So she would throw up what she just ate to make room. In those moments, Gibson says, she sometimes worried that she might tear open her stomach or esophagus. These injuries can be a rare, and sometimes deadly, result of binge eating.

Gibson’s case is extreme. But she has plenty of company. In 2013, binge eating became an officially recognized mental diagnosis. Statistics show that it’s now the most common eating disorder; about 1 in 28 women and 1 in 50 men have it at some point in their lives. That’s about three times the rate for anorexia and bulimia combined.

1 of 36 vs. 1 of 167A U.S. adult's lifetime chance of having binge eating disorder vs. anorexia nervosa.Binge eating -- as with all eating disorders -- has complex psychological and physiological roots. One of its key drivers is a weakness for sweets and other mouthwatering but unhealthy foods.

This hedonic reward system “is what allows us to eat the pumpkin pie after a Thanksgiving dinner” even if your gut is busting, says Frank Greenway, MD, a chief medical officer at Pennington Biomedical Research Center in Baton Rouge, LA.But why are some people able to stop after a few bites of a treat while others raid their candy stash again and again and again?

The difference, researchers think, is a mix of our genes, our environment, and whether our inhibitory response -- the brakes in our brain that help us resist impulsive behavior, including the urge to eat -- is strong enough.“I think it’s true that some people have a much more exaggerated hedonic response to food that other people … some people respond really strongly and some people just have a very kind of mild one,” says psychologist Graham Finlayson, PhD, who leads the Appetite Control & Energy Balance Research group at England’s University of Leeds.

Hedonic eating is “a huge problem. And it’s not just people with binge eating.”- Stephanie Manasse, PhD, an assistant research professor at Drexel UniversityFinlayson and Lowe have developed questionnaires that help place people on a hedonic eating scale. Currently, these are used only for research, so it’s difficult for members of the public to learn exactly why they overeat, and whether a strong hedonic drive may be to blame.

People who binge, as Angie Gibson does, are recognized to have strong hedonic appetites. But what about the rest of us? Hedonic eating can become a struggle for almost anyone, even if they don’t binge eat, says Stephanie Manasse, PhD, an assistant research professor at Drexel University in Philadelphia. 

“I think it’s a huge problem,” she says. “We have the information in order to help people lose weight, right?” Manasse says. We can cut calories, exercise more, plan menus of healthy meals and snacks. But over a lifetime, her colleague Lowe says, the constant effort not to yield to temptations becomes a losing battle for many people who become overweight, and especially for those who are obese. 

“We are surrounded by so many good-tasting foods that we gradually consume more calories than we need and gain more and more weight over time,” he says.Pumping the Brain’s BrakesRight now, there’s little to help people quench a powerful hedonic drive. Manasse is part of a team at Drexel that is testing a new technology to help people overcome eating just for pleasure. It’s called inhibitory control training.

For people with strong hedonic appetites, being surrounded by highly inviting foods, she says, is akin to pressing a car’s gas pedal. So Manasse hopes to train people on how to hit the brakes.Study participants strap on virtual reality goggles that plunk them down in the aisles of a grocery store. Before they start, the players are coached to press a certain key for healthy foods -- eggplants, black beans, oranges and the like -- that appear on the screen with green checks. The game gradually speeds up to train the players to press the correct key as reflexively as possible.

Every once in a while, the game flashes a trick. A Snickers bar. A can of Pepsi. A box of Frosted Flakes cereal. The players are meant to skip pressing the key for these no-go foods.Inhibitory control training is based on something called the dual-process model of self-control. The idea is that everyone has an impulsive side that gives into rewarding temptations, but we also have a rational side of our brains that can stop those impulses to align our behavior with our goals.

The aim of the game is to strengthen the rational thought process so that you reach for that stalk of broccoli instead of a bag of pretzels.Researchers at Drexel University are testing ways to help people resist unhealthy temptations. In this exercise, participants wearing virtual reality goggles “shop” for groceries while learning to make split-second decisions to avoid foods high in sugar.

So far, the evidence that this works is mixed. Players seem to learn the technique and their scores improve. But so far, it hasn’t always translated into real-world results. People get better at the virtual training, but they may not lose weight.But Manasse says she’s seen some encouraging results from her tests. In a recent study, she and her team recruited people who said they ate sugary foods at least three times a day. The divided 106 study participants into two main groups. One group received inhibitory control training, while the other went through a sham exercise. Everyone then went on a no-sugar diet. They completed their training every day at home.

By the end of the study, the two groups showed little differences in weight loss. But when Manasse parsed the data more closely, she found that the training paid off the most for people whose cravings for sweets were the strongest. After 8 weeks of inhibitory control training, those who were the most intensely tempted by sugar lost about 50% more weight than their counterparts in the placebo group.

This research isn’t yet ready for prime time. For one thing, it’s unclear how the training will translate to real life, bombarded as we are with frozen burritos, flavored coffee drinks, and cookies in easy reach.Medications to Curb CravingsFor now, people like Gibson have to turn elsewhere for help.

As her weight ballooned, her campus health center steered her to counseling and medication. Specifically, a combination therapy of the antidepressant bupropion and the addiction drug naltrexone. That’s exactly the mix in the FDA-approved weight loss medication Contrave. The way the drugs work to aid weight loss isn’t clear, but studies suggest the medications enhance each other as they curb appetite and the reward value of foods.

Bupropion was developed to treat depression. The FDA later approved it, under the brand name Zyban, to help people quit smoking. It helps to tamp down cravings so that puffing on a cigarette feels less satisfying. Zyban also seems to boost energy, so that you burn a few extra calories. That prompted drug researchers to test a bupropion-naltrexone combination -- which seems to become more potent when prescribed in tandem -- to treat obesity. That drug eventually became Contrave.

Most weight loss drugs influence both the reward and hunger centers in the brain, says Greenway of Pennington Biomedical. But some drugs are better at cutting your appetite, while others work better at blunting the reward circuitry.But messing with the brain’s reward system can have serious downsides. The once-promising weight loss drug Rimonabant is one such cautionary tale.

Rimonabant blocked the brain’s receptors, or docking sites, from connecting to the body’s feel-good chemicals in the endocannabinoid system. THC, the main mind-altering ingredient in pot, binds to these same receptors to spur euphoria, relaxation, and, less welcome, the marijuana munchies.

In animal studies, rats given Rimonabant quit seeking out addictive drugs like nicotine and fattening foods. Human subjects not only lost weight on Rimonabant, but their levels of “good” cholesterol rose and their blood sugar levels dropped.But American regulators discovered that many people in Rimonabant’s clinical trials had dropped out after new episodes of depression and anxiety. Two had died by suicide. Many more reported urges to kill themselves. The FDA never approved Rimonabant in the U.S. The once-wonder drug was yanked off the markets in the U.K. and around the world.

Rimonabant’s failure highlighted the danger that limiting pleasure and reward may rob people of happiness and the will to live. Yet for Gibson, alone and stressed in school and subsisting on fast food, medication was a godsend. For the first time in her life, food didn’t consume most of her waking hours.

“I wasn’t daydreaming about corn dogs. I only thought about food when I was actually hungry,” she says. Much like someone addicted to alcohol and trying to stay sober, Gibson used to count the days between her binges. Now she could simply stop eating once she felt full.

She shed almost 100 pounds and quit eating almost heedlessly.Angie Gibson today. She’s wearing one of the outfits she was considering for her interview for medical school.Listening Better to Hunger CuesOther ways to calm a raging appetite include exercise, more sleep, and other lifestyle changes. As anyone who has ever tried to break an unhealthy habit knows, sticking to those pledges is easier said than done.

It’s extremely difficult to shed weight solely through exercise. The reason is that it's all too easy to out-eat a workout. Just a few cookies can undo the calories you burned in your half-hour on the treadmill.But new research hints that exercise may help you lose weight in an unexpected way. Physical activity may help your body get back in tune with its actual hunger cues, making it less likely for hedonic urges to take over.

“I do think that exercise has a role in improving appetite and maybe making you less likely to overeat,” says David Stensel, PhD, a professor of exercise metabolism at England’s Loughborough University.The best appetite suppressant among exercises is high-intensity interval training, the kind of workouts that make your muscles “burn.”

Stensel says research shows this is particularly true for people who sit most of the day. Being very inactive can throw off your appetite, so it’s harder to tell if you’re dreaming about a chocolate bar because you’re hungry or because your bored or stressed mind is reacting to hedonic pangs.

Even just a little bit of exercise, like taking regular walks during the day or gardening, can make you more sensitive to actual hunger and prompt you to be less tempted by hedonic cravings.But the best appetite suppressant among exercises appears to be high-intensity interval training, or HIIT, according to research by Tom Hazell, PhD, an associate professor at Wilfrid Laurier University in Toronto. In HIIT, short bursts of jumping jacks, lunges, and other explosive moves allow lactate to build up in the blood. Lactate is the substance that makes hard-working muscles “burn.” In his studies, people who saw larger increases in the amount of lactate in their blood also saw bigger drops in the hunger hormone ghrelin. Hazell thinks lactate could inhibit the release of this key hormone, but he’s still working to prove that.

Sleep, too, helps wrangle appetite.Research has shown that a lack of ZZZs makes people hungrier the next day. One study docked women’s slumber by nearly 3 hours. Sleep-deprived subjects then ate more calories, including more junk food, compared to when they got a full night’s rest. New studies show that sleepy brains may crave high-calorie foods by making them seem more alluring.

Today, Angie Gibson relies on every tool and trick to keep her weight in check. But it’s a constant battle. A recent trip to the gym lured her into thinking she could enjoy a milkshake.And unexpected obstacles can throw her off her game. For instance, the start of the COVID-19 pandemic made her anxiety unbearable. Her regular gym closed. And she lost the desire to cook.

So Gibson went back to see a counselor, who talked to her about her options. They added a medication to help her control her anxiety. She’s starting to cook at home again.“I'm getting out of it,” she says.She’s staying focused on her goal of getting into medical school by starting a YouTube channel for other pre-med students. She now wears size 1X tops, smaller than what she wore in the sixth grade.

And Gibson shares her story with anyone who needs to hear it.“I try not to keep secrets,” she says. “My life is my life. I don't think there's really a need to be embarrassed.”Could I Have an Eating Disorder?There are three main types of this mental illness. If you or a loved one needs help or support, call or text the National Eating Disorders Association Helpline at 800-931-2237.

Anorexia NervosaThis leads to stark weight loss from limiting calories or types of foods. Teens are most vulnerable to it, but it can affect people at any age. Signs of it include:Dressing in layers to hide weight loss or for warmthFrequent comments about feeling fat

Not enough weight for their age, height, and buildExcessive, rigid exercise habitsBulimiaThis is a cycle of bingeing on food, followed by vomiting, too much exercise, or using diuretics or laxatives. Signs include:Empty wrappers or other clues that large amounts of food were eaten very quickly

Sounds, smells, and signs of purging; bathroom visits after mealsDrinking a lot of water or diet beverages and using mouthwash or gumEroded or stained tooth enamel or sensitive teethBinge EatingIt’s when you repeatedly and secretly eat a lot of food quickly, usually in less than 2 hours. Signs include:

Feelings of disgust, depression, and guilt after bingeingStealing or hoarding food in strange placesOrganizing your life around bingeing sessionsReviewed by Brunilda Nazario on February 10, 2021 Angie Gibson, cancer clinical trial protocol reviewer, University of Alabama at Birmingham.

Michael Lowe, PhD, professor of psychology, Drexel University, Philadelphia.Kevin Hall, PhD, section chief, integrative physiology, Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD.Graham Finlayson, PhD, chief, Appetite Control & Energy Balance Research group, University of Leeds, U.K.

Frank Greenway, MD, chief medical officer, Clinical Trials Unit, Pennington Biomedical Research Center, Baton Rouge, LA.Stephanie Manasse, PhD, assistant research professor, Drexel University, Philadelphia.David Stensel, PhD, professor of exercise metabolism, Loughborough University, U.K.

Tom Hazell, PhD, associate professor, Wilfrid Laurier University, Toronto.The Journal of Clinical Endocrinology & Metabolism: “Changes in the Homeostatic Appetite System After Weight Loss Reflect a Normalization Toward a Lower Body Weight.”BMJ Open

: “Ultra-processed foods and added sugars in the US diet: evidence from a nationally representative cross-sectional study.”National Eating Disorders Association: “Warning Signs and Symptoms.”The Lancet: “Rimonabant: obituary for a wonder drug -- Editorial.”

Nature: “Rimonabant adds appetizing choice to slim obesity market.”Journal of Obesity: “Rimonabant: From RIO to Ban.”Nutrients: “Increased Hunger, Food Cravings, Food Reward, and Portion Size Selection after Sleep Curtailment in Women Without Obesity.”

The Journal of Neuroscience: “Sleep Deprivation Selectively Upregulates an Amygdala-Hypothalamic Circuit Involved in Food Reward.”Sleep Foundation: “Sleep and Overeating.” Read more: WebMD »

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