David Ludwig

What We Know of Obesity and Low-Fat Diets Might Be Wrong

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DAVID LUDWIG IS RETHINKING HOW WE EAT.

In the late 1990s, David Ludwig brought 12 obese teenage boys into his clinic for the day, and fed them each prescribed meals. It was a simple experiment: The meals all had the same number of calories, but contained different kinds of food.

At the time, it was generally believed that a high-fat diet led to a high-fat body: You were what you ate. Americans had spent decades cutting down on the fat in their foods, in an effort to be leaner and more healthy. And yet studies consistently showed that this didn’t work—people on low-fat diets experienced high rates of hunger, and any weight they lost was soon regained. Ludwig wanted to know what was going wrong. Maybe it had to do with the kinds of calories we ate, not just how many.

Ludwig, who now treats obesity at Boston Children’s Hospital and is a professor of nutrition at the Harvard School of Public Health, fed his teenage subjects meals that all had different ratings on the glycemic index, which measures how rapidly sugar rises in the bloodstream after a meal. For example, instant oatmeal is high-GI: Highly processed and refined, it is quickly digested and dumps sugar into the blood in minutes. But old-fashioned oatmeal made with steel-cut oats, a lower-GI food, gets digested much more slowly, doling out sugar into the bloodstream little by little.

Over the next few hours, Ludwig and his team monitored how hungry the teenagers felt, and how much they consumed in snacks. Teenagers on the high-GI regimen became ravenously hungry and ate a lot of snacks after the meal—80 percent more calories in snacks that day than those who had the low-GI meals. “If just half of that calorie difference occurred day after day,” Ludwig says, “it could explain most of the obesity epidemic in the United States.”

Later, Ludwig followed 21 overweight young adults over a period of three months while feeding them three different diets: low fat with high carbs, low carbs with high fat, and a diet with an equal amount of fat and carbs.

In the end, the low-fat diet had a strongly negative effect: When subjects were on it, they burned 325 fewer calories per day. That is, their metabolism slowed dramatically compared with when they were on the low-carb diet, which did a much better job of burning calories rather than storing them. In effect, it was as if those on the low-carb, low-GI diet put in an extra hour of exercise every day without lifting a finger.

If what Ludwig was seeing was correct, it meant that everything we thought we knew about food was wrong. The body is not just a gas tank. A calorie is not just a calorie. As Ludwig’s colleague Mark Hyman, an author and physician at the Cleveland Clinic, says, “Fo od is not just food—it is information used by the body.”

It also meant that the past 40 years of food advice had been a terrible, costly mistake.

For decades, the advice about food and obesity from nutritionists and the government had a strong, simple message: Eat less fat. The food industry responded with a massive campaign of substitution to get the fat out of foods. “Fat free” and “lower fat” became almost mandatory marketing points. Hostess offered low-fat Twinkies, and Nabisco offered fat-free SnackWell’s devil’s food cookies. It worked: At the start of the 1960s, our diets were about 42 percent fat; now they are 33 percent fat.

But we didn’t get any healthier. In the early 1960s, 13 percent of adults were obese and only about one percent had type 2 diabetes. Now, 35 percent of adults are obese and 13 percent have type 2 diabetes.

“Despite eating less fat, we are fatter than ever before,” Ludwig says. What was going wrong? And how could it be fixed?

Throughout the history of the species, humans have been used to natural, largely unprocessed foods that take time to digest and deliver energy to the bloodstream. This is the natural pace of eating and energy: digestion over hours, not minutes.

But when we cut the fat out of our diet, a problem emerged: Without the fat, foods didn’t taste as good, so the industry replaced fat with refined carbohydrates. The result: highly processed, refined foods. For the past 20 years, Ludwig has been studying the effects of these new edibles, which he refers to as essentially “pre digested food.”

When these carbohydrate-rich foods rush-deliver sugars to the blood, the body reacts by producing large amounts of insulin.

And insulin is the signal that sends incoming energy off to be stored, rather than burned. “So much insulin is secreted when we eat these rapidly digested carbohydrates that it drives all our nutrients into storage in the few hours after a meal,” Ludwig says. But that leaves the body without anything to burn. It’s like depositing money in a bank but not leaving yourself any cash on hand.

“When calories are cut like that, the brain perceives starvation. It doesn’t register that there are plenty of calories still stored in fat cells. It just sees that there aren’t enough calories in the blood. It thinks that it’s a famine; there’s not enough food. It doesn’t matter how many calories are stored in your fat cells. If your blood sugar is crashing, your brain is at immediate risk.”

A few hours after eating a high-GI meal, the rush of sugar passes, and then the levels of sugar and other fuels, especially fatty acids, in the blood crash. The low level of calories in the blood now causes hunger and sends out stress hormones.

“The body [perceives] this as a crisis…a metabolic crisis,” Ludwig says. “So it’s not what happens at the meal or an hour or two later. It’s what happens four hours later. That’s the time when you either snack or not, or if you’re sitting down to your next meal [you choose] normal-sized or supersized [portions] based on your hunger.”

This is a problem for dieters: When people cut back calories and start to lose weight, “The body begins to fight back,” Ludwig says. And the first defense is to raise the level of hunger. “We can ignore it for a few hours, or a few days. But imagine feeling desperately hungry day after day without relief. And the longer you continue on the diet, the more severe the hunger becomes.”

Ludwig’s research also undermines a lot of our prejudices against those who struggle with their weight. “We as a culture seem to believe that people with this particular medical problem have a more fundamental character defect than people with almost any other medical problem,” he says. “We assume they just lack the willpower to do what they know is right for them. We blame them. It is patently false.”

Instead, Ludwig says, the American diet “puts our hormones and blood sugar through a roller-coaster ride—meal after meal, day after day.… If these theories are right, this explains a substantial amount of weight gain observed over the last 40 years.”

When Ludwig gets peckish after lunch, he turns to the snacks stashed around his office. He opens the top drawer of his desk to show me: “I usually have a bunch of nuts here, and…” There, in a red wrapper, is a big bar of dark chocolate. “I recommend a minimum of 70 percent [cocoa],” he says. High-fat foods. And the jar next to the desk, with a spoon beside it?

Raw coconut butter. Loads of fat. Does he spread it on something? “No, just eat a couple of spoonfuls in the middle of the afternoon.”

As much as he can, Ludwig and his wife, Dawn, a master chef, eat according to his new theory of food—they favor slow-digesting foods without a lot of processed carbohydrates. Their seven-year-old son helps make dessert: dark chocolate with a dollop of peanut butter on it. They serve tea with heavy cream only, not milk.

Together, the Ludwigs are trying to bring this new science to the mainstream, to change the way Americans eat. They’ve recruited 235 people—some at Boston Children’s and some across the U.S.—to go through a 16-week training course in their new concept of healthy eating. Dawn, who has trained chefs and home cooks for years, worked with David to put together a manual and a step-by-step program, the object of which is partly to help subjects lose weight, and, more important, to establish sustainable habits of cooking and eating.

“This is a lifestyle, not a diet,” she says. The people in the program don’t count calories, but instead learn to choose foods that will make them feel satisfied and not hungry, while eliminating a lot of highly refined foods. Their program forms the basis of Ludwig’s new book, Always Hungry? Conquer Cravings, Retrain Your Fat Cells & Lose Weight Permanently. The book is due to be released on January 5.

At the same time, Ludwig and his colleagues have embarked on one of the largest and longest feeding studies ever attempted—following 150 students and faculty at Framingham State University, for an entire academic year, on controlled diets. The entire group will first lose 10 percent or more of their weight on a start-in diet, then be switched for the rest of the year to one of three diets: 20 percent fat with 60 percent carbs; 40 percent fat with 40 percent carbs; or 60 percent fat with 20 percent carbs.

At Framingham State, the study has its own kitchen setup and is careful to offer appealing dishes that are similar for each group. For example, a Mexican meal will have similar flavors but with different proportions or kinds of foods.

They’re looking to provide more evidence that what you eat is as important, if not more, as how much you eat. And there’s evidence that Ludwig’s work is having an effect.

This year, for the first time in more than three decades, the federal Dietary Guidelines Advisory Committee, a group of scientists who set government nutrition policies, removed their limit on fat, and they no longer are recommending low-fat foods to treat obesity. It is a revolutionary shift toward worrying more about processed carbs than fat.

“The limit on total fat is an outdated concept, an obstacle to sensible change that promotes harmful low-fat foods, undermines efforts to limit refined grains and added sugars, and discourages the food industry from developing products higher in healthy fats,” Ludwig and his colleague Dariush Mozaffarian wrote in the New York Times after the committee’s recommendations were published. “Fortunately, the people behind the Dietary Guidelines understand that. Will the government, policy makers and the food industry take notice this time?”

If they do, it will largely be because of the efforts of Ludwig and his colleagues.

“The calorie-balance approach to weight control, enshrined in the low-fat diet, has proven utterly ineffective,” Ludwig says. “But with a focus on food quality rather than calories, we can put biology back on our side to lose weight without the struggle.”

Are All Calories Created Equal?

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 Are all calories equal?

 

Plain sweet potatoes or pumpkin pie, turkey or Tofurkey, a calorie is still a calorie. At least, that’s what dieters have been told for the past half-century. Now, experts don’t agree

“By and large, we’ve been taking an accounting approach to weight loss,” says Dr. David Ludwig, a professor of nutrition at the Harvard School of Public Health. By that he means, health scientists have traditionally focused on the number of calories coming in versus the number of calories going out. But there are a lot of problems with that approach, he says. For one thing, it’s really tough to accurately keep track of your daily calorie intake. “Being off by just 100 calories a day could add up to a hundred pounds over a lifetime,” he says.

If burning more calories than you consume would keep you skinny, a low-fat diet should be the answer to all your diet prayers. That’s because, compared to protein or carbohydrates, fat contains roughly twice the number of calories, ounce for ounce. But Ludwig says low-fat diets have proved ineffective when it comes to losing weight. “Mediterranean or low-carbohydrate diets outperform a low-fat diet every time, and that wouldn’t be true if calories were the only measure that mattered,” he adds. (Mediterranean diets and others like the now-trendy Paleo diet are both high in fat, comparatively speaking.)

In reality, Ludwig says the body responds differently to calories from different sources. “Your weight is regulated by a complex system of genetic factors, hormonal factors, and neurological input, and not all calories affect this system the same way,” he explains.

As for fat: “Some naturally high-fat foods are among the most healthful we can eat in terms of promoting weight loss and reducing risk for diabetes and heart disease,” he explains, listing off foods like nuts, avocados, and many types of fish. “If you’re counting calories, you would want to eat these foods sparingly because they’re dense in calories. But they’re also very filing.”

Refined carbohydrates, on the other hand—like those found in white bread, cookies, crackers, and breakfast cereals—raise your blood’s level of the hormone insulin, which signals to your body that it needs to store fat cells. Also referred to as high-glycemic foods, these refined carbs pass through your digestive system quickly—which is why you can eat a whole bag of potato chips and feel hungry 15 minutes later, Ludwig says.

Dr. Richard Feinman, a professor of cell biology at the State University of New York Downstate Medical Center, compares insulin to a faucet handle. The more your blood’s amount of the hormone rises, the more the faucet opens and the more fat your body stores.

Feinman has looked at calories from the perspective of thermodynamics—or the laws that govern heat and energy. Like Ludwig, he says the idea that calories from different macronutrient sources would have the same effect on your body is silly. Put simply, it doesn’t make sense that “a calorie is a calorie” because your body uses the energy from different foods in a variety of ways, Feinman explains.

The big lesson here is that people need to look at food as not just a collection of calories, experts say. By cutting out refined carbs and eating more protein and healthy fats, which help you stay full without triggering the storage of fat cells, “You can work with, as opposed to against, your body’s internal weight-control systems,” he says. “That will make weight loss more natural and easy.”

Whole-Grain Foods Not Always Healthful.

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Often synonymous with good health, whole grains may lack heart-healthy fiber—in fact, some processed forms increase cardiovascular risks

Last month the American Society for Nutrition (ASN) reaffirmed in a report that fiber-rich whole grains lower the risks of diabetes and heart disease. Media outlets such as Reuters duly reported the news, but many failed to point out a crucial detail: some whole grains may do nothing to reduce disease risks. In fact, many foods legally marketed as whole grains could actually harm health.

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The term “whole grain” might evoke an image of a whole, intact grain—that is, a fiber-rich coating of bran surrounding a starchy endosperm and a small reproductive kernel known as the germ. But in a definition created in 1999 by the American Association of Cereal Chemists (AACC) International, an organization of food industry professionals and scientists, and adopted by the U.S. Food and Drug Administration in 2006, “whole grain” refers to any mixture of bran, endosperm and germ in the proportions one would expect to see in an intact grain—yet the grains can be, and usually are, processed so that the three parts are separated and ground before being incorporated into foods. (Refined grains, on the other hand, are grains that have been stripped of their bran and germ.) For a food product to be considered whole grain, the FDA says it must contain at least 51 percent of whole grains by weight. Compared with intact grains, though, processed whole grains often have lower fiber and nutrient levels.

In what it calls a scientific statement the ASN reviewed studies published about whole grains between 1965 and 2010. Descriptions in many studies did not conform to the current definition in that they considered foods such as wheat germ and bran cereals to be whole grain. (Both are now considered partsof a whole grain.) Ultimately, the researchers found that the only whole-grain-rich diets that reduced the risk of heart disease and type 2 diabetes were those that included bran as a whole grain or those that contained high amounts of fiber. Studies of “whole grains using the currently accepted definition don’t have enough data to support them for preventing these different chronic diseases,” says co-author David Klurfeld, the national program leader for human nutrition in the Agricultural Research Service at the U.S. Department of Agriculture.

Missing fiber
One problem with the current definition of “whole grain” is that it doesn’t account for fiber—and many whole grain products on supermarket shelves contain very little. An individual would have to eat 10 bowls of Multi-grain Cheerios, 16 slices of whole-wheat bread, or nine cups of brown rice to get the fiber recommended for an American adult for one day. “There’s nothing wrong with eating brown rice, but you can’t expect health benefits if you’re going to be eating brown rice as your source of whole grains,” Klurfeld explains.

The common processing of whole grains—which can involve grinding, puffing and flaking them—can also impact their healthfulness. Processing can make whole grains tastier; it can give them a longer shelf life, too, by removing fats from the outer layer of the grain that can turn rancid. But some processing techniques have been shown to degrade natural antioxidants and reduce fiber content. In fact, the AACC International recently proposed modifying its definition of “whole grain” to allow for some nutrient losses during processing.

Individuals also absorb the sugars from some processed whole grains more quickly than they do those from intact whole grains, triggering blood sugar spikes that can “possibly increase hunger, lead to overeating and increase the risk for diseases related to insulin resistance, like diabetes and heart disease,” says David Ludwig, a professor of nutrition at the Harvard School of Public Health. For instance, bread made from 80 percent–whole-wheat kernels is absorbed much more slowly than bread made from ground whole wheat. When a person eats intact grains, the body has to break down the outer bran before digesting the inner endosperm and germ. Ground grains often don’t provide these metabolic brakes.

Fast-cooking penalty
But even when whole grains aren’t ground, they can be processed in ways that can cause metabolic problems. In a 1999 study Ludwig and his colleagues split 12 obese teenage boys into groups. Some were given a breakfast of instant oatmeal, in which whole oats have been rolled and steamed so that they cook quickly. Other boys were given steel-cut oatmeal, comprising whole oats that have been sliced but not steamed. Although both meals had the same calorie and fiber content, the instant oats triggered much larger blood sugar spikes (a reflection of how quickly they were absorbed) and caused the boys to consume 53 percent more calories at lunch than the boys who ate the steel-cut oats. (A third group of boys were given identically caloric breakfasts of vegetable omelets and fruit and ate 81 percent fewer calories at lunchtime than did the instant oat eaters.) Food companies lump ground whole grains, partially processed grains and intact unprocessed grains together under the same broad category of “whole grains,” so it’s difficult for consumers to know which they’re getting.

Whole-grain foods can also contain unhealthy additives. In January Ludwig and other Harvard researchers compared the nutrient composition of 545 grain products and found that those labeled with the “Whole Grain” stamp, an industry-sponsored label for foods containing at least eight grams of whole grains per serving, contained more calories and sugar than those without the stamp. They were also more expensive. When a food is marketed as containing whole grains, “it takes on a ‘health halo,’ and companies can slip in all sorts of junk without people recognizing what they’re getting,” Ludwig says. Joanne Slavin, professor of food science and nutrition at the University of Minnesota, who served on the committee for the 2010 Dietary Guidelines for Americans, agrees that many foods with whole-grain labels are “really not very nutritious food products.”

More isn’t good
So how did “whole grain” become synonymous with “healthy”? Part of the confusion stems from the U.S. dietary guidelines, which recommend that individuals triple their consumption of whole-grain foods from an average of one ounce per day to three ounces. But the goal is for Americans to replace half of their refined grains with whole grains, not to eat whole grains in addition to the refined ones they have been eating, Slavin explains. “We don’t want people to think that because a food has whole grains, they should eat more of it,” she says. “Grains in general are overconsumed in the U.S.”

Another reason whole grains may seem more healthful than they really are: people who eat lots of them tend to make smarter lifestyle choices in general. A 2006 study (pdf) reported that the quartile of people who eat the most whole grains are less than half as likely to smoke and 25 percent more likely to regularly exercise as the quartile of people who eat the least whole grains.

If one clear piece of advice is emerging about whole grains, it is that individuals should buy whole grains that are high in fiber: All of the diets that reduced disease risk in the ASN’s review were high in fiber or fiber-rich bran, and Ludwig and his colleagues found in their 2013 study that whole-grain foods with a ratio higher than one to 10 of fiber to total carbohydrate also contained less sugar, sodium and trans fats than other whole-grain products. People should consider cooking with intact whole grains, too, such as whole-wheat berries or spelt. And when in doubt, consumers should always trust their nutritional instincts. “If it’s a whole-grain cookie, you probably don’t need it,” Slavin says. Deep down, most people already know that.

Source: http://www.scientificamerican.com

Can it! Soda studies cite stronger link to obesity.

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As Americans debate what is most to blame for the nation’s obesity epidemic, researchers say they have the strongest evidence yet that sugary drinks play a leading role and that eliminating them would, more than any other single step, make a huge difference.

Three studies published Friday in the New England Journal of Medicine represent the most rigorous effort yet to see if there is a link between sugar-sweetened beverages and expanding U.S. waistlines.

“I know of no other category of food whose elimination can produce weight loss in such a short period of time,” said Dr. David Ludwig, director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital, who led one of the studies. “The most effective single target for an intervention aimed at reducing obesity is sugary beverages.”

Previous research on the subject has been mixed, and beverage makers fiercely contest the idea that a single source of daily calories can bear so much responsibility.

“We know, and science supports, that obesity is not uniquely caused by any single food or beverage,” said the American Beverage Association (ABA) in a statement. “Studies and opinion pieces that focus solely on sugar-sweetened beverages, or any other single source of calories, do nothing meaningful to help address this serious issue.”

The NEJM studies, as well as an editorial and opinion pieces on the topic of sugary drinks and obesity, land as concern about obesity and its impact on public health is rising.

A report released this week projected that at least 44 percent of U.S. adults could be obese by 2030, compared to 35.7 percent today, bringing an extra $66 billion a year in obesity-related medical costs.

Last week, New York City adopted a regulation banning the sale of sugary drinks in containers larger than 16 ounces at restaurants and other outlets regulated by the city health department.

Sugary drinks are in the crosshairs because from 1977 to 2002 the number of calories Americans consumed from them doubled, government data show, making them the largest single source of calories in the diet. Adult obesity rates, 15 percent in the late 1970s, more than doubled in that period. The ABA points out, however, that consumption has since fallen, yet obesity rates keep rising.

Although most observational studies find that people who drink sugary beverages are more likely to be obese than people who do not, no cause-and-effect has been proved. People who drink sugary beverages, especially children, also watch more TV and eat more calorie-dense fast food, raising the possibility that liquid sugar is not the main culprit.

A 2008 analysis of 12 studies, led by a scientist who went on to work for the ABA, concluded that the association between sugary drinks and body-mass index (BMI) “was near zero.”

Studies in which children cut their intake of sugary drinks found modest benefits, but “they were considered unconvincing,” said Martijn Katan of VU University in Amsterdam: “Most had a small number of subjects and followed them for only a short time.” He and his colleagues aimed to do better.

BUILDING A BETTER STUDY

For DRINK (Double-Blind Randomized Intervention in Kids), they gave 641 children aged about 5 to 12 and with a healthy BMI of just under 17 one 8-ounce (250 milliliter) noncarbonated drink per day, sweetened artificially or with sugar. The sugar-free drinks were specially formulated to look and taste like sugary ones so the kids would not know which they had.

About a quarter of the kids stopped drinking the beverages. Among those who stuck it out for 18 months, the sugar-free kids gained less body fat, 2.2 pounds (1 kilogram) less weight, and 0.36 units less BMI than the sugary-drink kids, the researchers report in the NEJM.

Why? There is good evidence that liquid sugar does not produce a feeling of fullness that other calories do. “When children substituted a sugar-free drink, their bodies did not sense the absence of calories, and they did not replace them with other food or drinks,” said Katan.

DRINK doesn’t answer whether switching to zero-calorie drinks would help obese kids. But another study in the same issue of NEJM suggests it might.

Researchers at Boston Children’s had zero-calorie drinks delivered to 110 obese 15-year-olds who had BMIs of about 30 (where obesity starts), counseled them not to drink sugary beverages and offered other support.

After a year the teens had cut their intake of sugary drinks from almost two a day to zero and their daily calorie intake by 454. They had gained an average of 3.5 pounds (1.6 kilograms). By comparison, 114 teens who continued to consume sugar-sweetened beverages gained 7.7 pounds (3.5 kg) on average and ten times the BMI units: 0.63 compared to 0.06.

Once the deliveries stopped the two groups diverged less. After two years, teens who had received the no-cal drink deliveries had gained 9.5 pounds (4.3 kg) and 0.71 unit of BMI, compared to the control group’s 11.2 pounds (5.5 kg) and 1.0 unit of BMI.

“It isn’t surprising that after the intervention stopped, old behaviors crept back,” said Ludwig of the New Balance Center. An “obesogenic” environment that promotes calorie-laden foods “overwhelms individuals’ ability to maintain behavioral change” such as avoiding sugary drinks.

Hispanic teens benefited the most: Those receiving no-cal deliveries gained 14 fewer pounds after one year and almost 20 fewer pounds after two. That raised the possibility that genetic factors influence the effect of sugary drinks.

To investigate gene-environment-obesity links, scientists at Harvard School of Public Health looked at 33,097 people from long-term ongoing health studies, such as the Nurses’ Health Study, identifying how many sugary drinks they consume and whether they have any of 32 genes linked to obesity.

The effect of genes on the likelihood of becoming obese was twice as large among people who drank one or more sugary drinks per day as among those who had less than one a month, the scientists report in the NEJM. In other words, belting back soda and sugary tea may turbocharge the genetic risk of obesity.

Conversely, eating a healthy diet devoid of sugary drinks keeps fat genes inactive. People with “fat genes” can be thinner if they avoid sugary drinks and other high-calorie foods.

Source: yahoo news.