How soup can help you lose weight

By Jack Challoner

In the battle to lose weight, hunger is the dieter's worst enemy. But research has revealed a simple aid to taming the appetite: soup. It's dieting's best kept secret says one science writer.

Imagine a typical lunchtime meal - say, chicken and vegetables with a glass of water. If you eat the food and drink the water, you will feel full for a couple of hours before hunger kicks in. But if you blend the food with the water - to make soup - you will stay hunger-free for much longer, and less likely to snack through the afternoon.

How can blending the food into soup make such a difference? The answer lies in the stomach. Scientists have used ultrasound and MRI scans of people's stomachs to investigate what happens after eating solid-food-plus-water meals compared with the same food made into soup.

After you eat a meal, the pyloric sphincter valve at the bottom of your stomach holds food back so that the digestive juices can get to work. Water, however, passes straight through the sphincter to your intestines, so drinking water does not contribute to "filling you up".

When you eat the same meal as a soup, the whole mixture remains in the stomach, because the water and food are blended together. The scientists' scans confirm that the stomach stays fuller for longer, staving off those hunger pangs.
The key to this low-tech weapon against hunger is a hormone called ghrelin. It is one of the major players in the body's appetite system.

Discovered as recently as 1999, ghrelin is released by specialised cells in the stomach wall.

'Cupcake circuit'
These cells produce a constant stream of ghrelin whenever the stomach is empty. The ghrelin travels via the blood stream to the brain's appetite centre, an organ called the hypothalamus. As a result, the hypothalamus screams "You are hungry - find food."

But whenever the stomach wall is stretched - when the stomach is full - the cells stop producing ghrelin, and the hypothalamus responds accordingly, turning off the appetite signal. The longer the stomach remains full, the longer you feel satisfied and the less you are likely to eat.

WHICH VARIETY IS BEST?
Vegetable soup is best
It produces a more consistent blend
And it generally has fewer calories than chicken or fish soup

The stomach gradually empties, more slowly for the soup than the solid meal plus water. The BBC staged an experiment for the programme 10 Things You Need to Know About Losing Weight to test this theory. In this experiment, and in previous experiments, participants reported feeling full for up to an hour-and-a-half longer than their solid meal counterparts.
Although some researchers refer to appetite as "the cupcake circuit", the mechanism behind human appetite evolved long before cupcakes were invented - at a time when food was scarce.

As a result, we are hardwired to eat high-calorie foods, which are unfortunately so abundant in the modern world.
Finding ways to control the appetite signal is crucial if we are to stave off the meteoric rise in obesity. Food scientists and pharmaceutical companies alike are on a major quest to find ways to do just that.

Could soup help address obesity?
Appetite is one of the most researched areas of weight-loss science. Unfortunately, the appetite system is complex, and still poorly understood.

There are probably dozens of hormones that play a role in regulating appetite. Of those that have already been discovered, there is one that is released after eating protein-rich meals (called PYY), one that is released by fat cells (leptin) and several that respond to the presence of any kind of food.

But of all the hormones that make up the appetite system, it is ghrelin that has caused the most interest. In addition to its role in sending the "stomach empty" signal to the brain, ghrelin also promotes fat storage. Even worse, it inhibits the breakdown of stored fat during times of weight loss. Inject ghrelin into the bloodstream of a rat and the animal eats insatiably - and quickly becomes obese.

In 2006, scientists at the Scripps Research Centre in the US developed a vaccine to counteract the influence of ghrelin, in an attempt to control appetite. It is still undergoing clinical trials - so for now, the best and simplest way to keep hunger at bay is to reduce your stomach's release of ghrelin: blend your food into a healthy, voluminous soup. The best sort? Vegetable soup, as it produces a more consistent blend and is generally lower calorie than chicken or fish soup.
Jack Challoner is a science writer and author of the website explaining-science.co.uk.

When Unhealthy Foods Hijack Overeaters' Brains

Food hijacked Dr. David Kessler's brain. Not apples or carrots. The scientist who once led the government's attack on addictive cigarettes can't wander through part of San Francisco without craving a local shop's chocolate-covered pretzels. Stop at one cookie? Rarely. It's not an addiction but it's similar, and he's far from alone.

Kessler's research suggests millions share what he calls "conditioned hypereating" — a willpower-sapping drive to eat high-fat, high-sugar foods even when they're not hungry. In a book being published next week, the former Food and Drug Administration chief brings to consumers the disturbing conclusion of numerous brain studies: Some people really do have a harder time resisting bad foods. It's a new way of looking at the obesity epidemic that could help spur fledgling movements to reveal calories on restaurant menus or rein in portion sizes.

"The food industry has figured out what works. They know what drives people to keep on eating," Kessler tells The Associated Press. "It's the next great public health campaign, of changing how we view food, and the food industry has to be part of it." He calls the culprits foods "layered and loaded" with combinations of fat, sugar and salt — and often so processed that you don't even have to chew much. Overeaters must take responsibility, too, and basically retrain their brains to resist the lure, he cautions. "I have suits in every size," Kessler writes in "The End of Overeating." But, "once you know what's driving your behavior, you can put steps into place" to change it.

At issue is how the brain becomes primed by different stimuli. Neuroscientists increasingly report that fat-and-sugar combinations in particular light up the brain's dopamine pathway — its pleasure-sensing spot — the same pathway that conditions people to alcohol or drugs. Where did you experience the yum factor? That's the cue, sparking the brain to say, "I want that again!" as you drive by a restaurant or plop before the TV. "You're not even aware you've learned this," says Dr. Nora Volkow, chief of the National Institute on Drug Abuse and a dopamine authority who has long studied similarities between drug addiction and obesity.

Volkow is a confessed chocoholic who salivates just walking past her laboratory's vending machine. "You have to fight it and fight it," she said. Conditioning isn't always to blame. Numerous factors, including physical activity, metabolism and hormones, play a role in obesity. And the food industry points out that increasingly stores and restaurants are giving consumers healthier choices, from allowing substitutions of fruit for french fries to selling packaged foods with less fat and salt. But Kessler, now at the University of California, San Francisco, gathered colleagues to help build on that science and learn why some people have such a hard time choosing healthier:
First, the team found that even well-fed rats will work increasingly hard for sips of a vanilla milkshake with the right fat-sugar combo but that adding sugar steadily increases consumption. Many low-fat foods substitute sugar for the removed fat, doing nothing to help dieters eat less, Kessler and University of Washington researchers concluded.
Then Kessler culled data from a major study on food habits and health. Conditioned hypereaters reported feeling loss of control over food, a lack of satiety, and were preoccupied by food. Some 42 percent of them were obese compared to 18 percent without those behaviors, says Kessler, who estimates that up to 70 million people have some degree of conditioned hypereating.
Finally, Yale University neuroscientist Dana Small had hypereaters smell chocolate and taste a chocolate milkshake inside a brain-scanning MRI machine. Rather than getting used to the aroma, as is normal, hypereaters found the smell more tantalizing with time. And drinking the milkshake didn't satisfy. The reward-anticipating region of their brains stayed switched on, so that another brain area couldn't say, "Enough!"

People who aren't overweight can be conditioned hypereaters, too, Kessler found — so it's possible to control. Take Volkow, the chocolate-loving neuroscientist. She's lean, and a self-described compulsive exerciser. Physical activity targets the dopamine pathway, too, a healthy distraction. Smoking didn't start to drop until society's view of it as glamorous and sexy started changing, to view the habit as deadly, Kessler notes. Unhealthy food has changed in the other direction. Foods high in fat, sugar and salt tend to be cheap; they're widely sold; and advertising links them to good friends and good times, even as social norms changed to make snacking anytime, anywhere acceptable. Retrain the brain to think, "I'll hate myself if I eat that," Kessler advises. Lay down new neural reward circuits by substituting something else you enjoy, like a bike ride or a healthier food. Make rules to resist temptation: "I'm going to the mall but bypassing the food court." And avoid cues for bad eating whenever possible. Always go for the nachos at your friends' weekend gathering spot? Start fresh at another restaurant. "I've learned to eat things I like but things I can control," Kessler says. But he knows the old circuitry dies hard: "You stress me enough and I'll go pick up that bagel."