Long-standing wisdom in the world of nutrition and weight loss has said a calorie is a calorie, and if you eat fewer calories than you expend, you will lose weight. Simple enough.

But there’s another theory that says some kinds of calories are more effective than others in helping manage weight. The idea, backed by a study published last year in the Journal of the American Medical Association, says a calorie from carbohydrates may have a more deleterious effect on people’s metabolism than a calorie from protein or fat.

In other words, what you eat matters, and not just how much.

The study, led by Dr. David Ludwig of Boston Children’s Hospital found low-carbohydrate diets that included more fat than other diets in the study had the most beneficial effects on metabolism.

Low-fat diets, on the other hand, slowed the rate at which a body burned calories just to function — to breathe, digest food and heal itself.

“The results of our study challenge the notion that a calorie is a calorie from a metabolic perspective,” the study’s authors wrote.

The micronutrients — carbohydrates, fat and protein — can influence metabolism and therefore weight loss, independent of calorie consumption, according to the study. The study concludes with a suggestion to cut carbs instead of fat for weight loss and cardiovascular disease prevention.

A personal experience

That is exactly the dietary guidance that has helped Teresa Edwards, of Bend, shed unwanted pounds and feel all-around better.

Edwards was one of many who tried the low-fat diets popularized in the 1980s. Low-fat diets tend to prioritize calorie restriction and often include a lot of carbohydrates. Edwards ate low-fat crackers and cookies, cereal with skim milk, light bread. Most of the foods she ate “had no nutrition with little calories and nothing to them, so you’d starve till you lost weight.” Then she would gain it back after she quit the low-fat diet.

As Edwards approached age 50 this year, although she was avoiding processed foods and eating healthy, she said she couldn’t stop her weight from ballooning. Her doctor recommended a nutritionist who advised she limit carbohydrates, including fruits at first, because carbs were wreaking havoc on her metabolism, she said.

Last October, hovering around 200 pounds on a 5-foot-5-inch frame, she switched to eating mostly meat and vegetables. Over time, she added in nuts and healthy oils. She eats small portions of some carbohydrates, such as whole grain pasta or rice or a wrap, for fiber sometimes. She eats a little bit of fruit and has the occasional carbohydrate indulgence, she said.

The most noticeable, consistent change, she said, is that she skips cereal for breakfast. Instead, she’ll have eggs, lean turkey bacon or uncured ham. She pays attention to portion sizes.

“It’s so simple and satisfying,” she said.

She’s lost 30 pounds and has kept it off. The rheumatoid arthritis she had for 10 years isn’t bothering her anymore; she stopped taking medications for it.

Her nutritional therapeutic practitioner, Gina Bailey of The Health Connection, said getting people on a low-carbohydrate diet that eliminates everything down to fruits is to “get control over sugar and sugar addictions,” she said.

“But I don’t think we need to live on low-carb diets long-term. Once the metabolism gets balanced we can burn some carbs when we eat them.”

After an initial period of an extremely low-carbohydrate diet, she advises clients to include legumes, which contain carbohydrates but are a great source of energy and protein, she said. Vegetables have carbohydrates but are something she advocates. “Instead of counting calories, control blood sugar by eating every three hours on average, and we’re never hungry. The choices should be protein, which also includes some fats at times — good healthy fats — and vegetables,” Bailey said. “Balance (that) with some fruits and grains. That, to me, is a more maintenance lifestyle.”

Carbs vs. fats

In Ludwig’s study published in JAMA, overweight and obese adult participants were first required to lose 12.5 percent of their body weight, a process that results in a body biologically adapting by burning fewer calories. Then, in a controlled-diet study, 21 adults participated in three different diet plans for four weeks each. The diets were: low-fat, low-glycemic index and low-carbohydrate.

(Low-glycemic index foods are more slowly digested carbohydrates, such as whole grains, legumes and other high-fiber foods. They generally have more fiber and fat than carbohydrates higher on the glycemic index, which tend to be more refined carbohydrates and digest more quickly. See the chart on this page.)

Low-fat diets in the study included 60 percent of calories from carbohydrates, 20 percent from fats and 20 percent from proteins.

Low-glycemic diets included 40 percent of calories from carbohydrates, 40 percent from fats and 20 percent from proteins.

Very low-carbohydrate diets included 10 percent of calories from carbohydrates, 60 percent from fat and 30 percent from protein.

Participants rotated among the three diets, consuming equal numbers of calories on each.

Researchers found those eating the least fat and most carbohydrates — the low-fat diet — burned fewer calories at rest and over the course of a day. The low-glycemic diet had intermediate effects on energy expenditure and the very low-carbohydrate diet had the most beneficial effects on energy expenditure and other components of metabolic syndrome, a handful of disorders related to cardiovascular disease and diabetes.

Those on the very low-carbohydrate diet burned about 67 calories more per day than those on the low-fat diet, when looking at resting energy expenditure, a measurement taken while study participants lie quietly prior to breakfast.

And there was an even greater difference in the “total energy expenditure,” which takes into account all ways that calories are burned, including physical activities throughout the day. Those on the very low-carbohydrate diet, which had comparably high proportions of fat, burned 300 calories more per day than those on the low-fat diet. (That is about the equivalent of calories burned by a 140-pound person on a one-hour walk.)

“A low-glycemic-load diet improves access to energy stores,” Ludwig wrote in an email. “Consequently, fat can be burned more effectively, supporting metabolism and reducing hunger.”

Although the very low-carbohydrate diet with the highest fat content had the most beneficial effects on energy expenditure and several metabolic components, it also created the highest cortisol levels in participants’ urine. Cortisol is a hormone the body secretes in response to stress. Some studies suggest that high cortisol levels can promote fat storage, insulin resistance and cardiovascular disease.

The low-glycemic diet appeared to have similar although smaller metabolic benefits compared with the very low-carbohydrate diet, and possibly without the physiological stress, authors wrote. “These findings suggest that a strategy to reduce glycemic load rather than dietary fat may be advantageous for weight-loss maintenance and cardiovascular disease prevention,” they summarized. The study did not measure weight loss but rather focused on metabolic functions.

The connection between carbohydrates and fat appears connected to insulin. Research says carbohydrates trigger hormonal responses that affect fat storage and hunger. High-glycemic foods stimulate higher blood sugar and insulin production and promote the uptake of glucose into the fat cells — potentially storing fat in a body. Calorie for calorie, high-glycemic meals stimulate more insulin secretion than low-glycemic meals, according to a paper about the glycemic index written by Ludwig, published in JAMA in 2002.

Ludwig also noted in this paper that a few hours after eating high-glycemic foods, blood sugar falls rapidly, triggering a reaction that results in increased hunger, in an attempt to restabilize the body.

Not so simple

A handful of popular diets have espoused a divorce with carbohydrates, suggesting that carbohydrates are the enemy in the fight with fat.

But carbohydrates can’t be entirely blamed for the obesity problem, said Julie Hood Gonsalves, a registered dietitian and associate professor of science and allied health at Central Oregon Community College. It’s not that simple, she said. Obesity and dieting are multifaceted issues, with everything from calories and micronutrients to genetics and behavioral habits at play.

While it’s true that carbohydrates create insulin and glucose in the blood stream, resulting in glucose in the fat cells, the same can be said to some extent of fats and proteins, she said.

“It doesn’t make sense to say it’s all about carbohydrates, when protein will do it, too,” Gonsalves said. “Scientists are trying to find the one thing that makes a difference. But in reality, we have not been able to say that’s it.”

Controlled studies like Ludwig’s look at individual components within food, usually over a short period of time. That’s not reflective of how people really eat.

There’s another hormone, called leptin, involved with appetite and metabolism. It is released by fat cells, Gonsalves said. High levels of leptin decrease one’s appetite. When a person loses weight, or fat, leptin levels go down, which stimulates the appetite.

“You can’t talk about insulin and fat and ignore everything else. If you’re not storing fat, you have this other powerful mechanism increasing your appetite,” she said.

And, she said, people have to be considered individually. What works for one might not for another. If a low-carb diet works for someone trying to lose weight, great, Gonsalves said. “But pay attention to the nutrients that might be missing.”

Weight is not the only indication of health, she emphasized. On some high-protein and high-fat diets, people might eliminate or minimize their intake of fruit and some vegetables, therefore reducing intake of antioxidants, fiber and folic acid. Whole grains have important fiber and magnesium, and milk products contain calcium and vitamin D.

“When someone goes on a low-carbohydrate, high-protein-fat diet to lose weight, they will likely lose weight. In fact, some studies show they will lose a little more with this type of diet than a low-fat, high-carb one,” she said.

However, research has shown that no diet — even low-carb — works particularly well over the long term.

But there’s a difference between dieting and making sustainable lifestyle choices.

Limiting carbohydrates at some level is probably a good thing, Gonsalves said, but she says people should eat fruits, vegetables and whole grains. Mainly, she said, avoid refined carbohydrates such as sugar and sweetened foods and refined white-flour products.

Over the past three decades, Americans have been eating more calories, and more calories from carbohydrates, and at the same time, the population steadily gained weight, Dr. Jennifer Marks wrote in a 2004 editorial when she was the editor of Clinical Diabetes, a publication of the American Diabetes Association.

“But are carbohydrates really the enemy or were we eating the wrong carbohydrates? Choosing fiber-rich carbohydrates, such as fruits, vegetables and whole grains, as well as foods low in saturated (fat), and preferably high in monounsaturated fats seems a sane course to follow.”

The Glycemic Index

The glycemic index ranks foods on a scale from 1 to 100 to help describe how quickly carbohydrates break down in the digestive system to form glucose, a source of energy.

Low-glycemic foods are generally described as slowly digested carbohydrates, such as whole grains, legumes and other high-fiber foods. Foods that digest more quickly, such as white bread or pasta, have a higher index. Foods ranked 100 are the equivalent of pure glucose. Fat and fiber tend to lower the glycemic index of a food, according to the American Diabetes Association.

Low-glycemic diets have been used to help people with diabetes keep their blood sugar under control. Eating a low-glycemic diet does not cause blood glucose levels to spike and increases a hormone that helps regulate the metabolism of fat and sugar. The American Diabetes Association ranks various foods on the 1-100 glycemic scale:

Low (55 or less)

100 percent stone-ground whole wheat bread

Oatmeal that is rolled or steel cut, oat bran, muesli

Barley, bulgar

Sweet potato, corn, yam, lima beans, peas, legumes, lentils

Most fruits, nonstarchy vegetables and carrots

Medium (56-69)

Whole wheat, rye and pita bread

Quick oats

Brown, wild or basmati rice, couscous

High (70 or more)

White bread or bagel

Corn flakes, puffed rice, bran flakes, instant oatmeal

Short-grain white rice, rice pasta, box mac ‘n’ cheese

Russet potato, pumpkin

Pretzels, rice cakes, popcorn, saltine crackers

Melons and pineapple

Source: www.diabetes.org