Taubman Scholar Dr. Charles Burant: All calories are created equal

Despite recent studies touting low-carb meal plans, the secret to weight loss is in the calorie count, says Taubman Scholar Dr. Charles Burant.

By Karen Dybis

 With two-thirds of American adults overweight or obese, the quest for a definitive weight-loss solution is an ongoing social, medical and public-health problem.

And while it is tempting to believe studies that claim to have cracked the calorie code, the best long-term diet answer beyond “eat less and exercise more” remains elusive.  In the end, the magic formula may never be found -- because it doesn’t exist.

So says Dr. Charles F. Burant, an obesity and metabolism expert and a Taubman Scholar at the A. Alfred Taubman Medical Research Institute. Dr. Burant believes a recent study that lauds the low-carbohydrate plan as the possible “Diet Champion” may not be worthy of this title.

“There may be a subtle error overlooked by investigators that could make the results not as impressive or with the champion not much different than the other two diets described in the study,” Dr. Burant says.

The Boston study

Conducted by Dr. David Ludwig of Boston Children’s Hospital and his colleagues, the study published  in June in the Journal of the American Medical Association was based on a clinical trial that attempted to determine which of three diets had the best outcome for people trying to maintain weight loss.

The study examined how much energy participants used following a significant weight loss.

To begin, researchers recruited 21 obese young adults and placed them on a strict diet that made them lose between 10 percent and 15 percent of their starting weight.

Afterward, the subjects were assigned to one of three diets:

•    The first was a traditional low-fat diet, based on American Heart Association recommendations. In that diet, participants avoided dietary fats and ate more whole grains, vegetables and fruit.

•    The second diet was described as one with a low-glycemic index, including foods that the body slowly digested and which kept participant’s blood-sugar levels regulated and insulin levels low. This diet would be akin to the popular Nutrisystem plan.

•    The final diet mirrored the Atkin’s Diet, or a low-carb/high fat and protein plan. Participants ate more meats and didn’t worry about their meals’ fat content. But they were asked to reduce the amounts of bread and pasta they consumed.

The researchers found that participants on the low-carb diet ‘burned’ 300 more calories more per day than those on the other plans. They concluded that this eating pattern will help people keep weight off over their lifetimes. The finding was pounced on by the media, including the New York Times – and the next great diet was born.

Not so fast

It may be the methodology used by the Boston researchers skewed the study results, Dr. Burant explained.

“Technically, it is a little difficult to explain, but essentially, they used two techniques to estimate energy expenditure,” he said.

One method employed specially ‘labeled’ water that is used to estimate the amount of energy being used. The more energy, the faster the ‘labeled’ water disappears from the body.  But to calculate the real energy use, you have to know how much water there is in the body.  For this they needed to have an accurate measure of lean body mass, mostly skeletal muscle.  

“When you’re on a low-carbohydrate diet, it changes the amount of water in your body. You lose a lot of weight on low carbohydrate diets at first because you lose glycogen, the storage form of glucose, because your body quickly uses the stored glucose when there isn’t much consumed.

“For every gram of glycogen mobilized, you lose three grams of water. The majority of this glycogen is in skeletal muscle and when you lose weight, the muscles ‘shrink’, sort of like a tomato shrinks when it sits on the shelf for too long – it loses water and shrivels a bit. ” Dr. Burant said.

“(The study) didn’t indicate whether the investigators took into account this muscle shrinkage, I think they would have indicated that if they did.  If they didn’t, then the lean mass would be incorrectly measured… throwing an error into the estimates of energy use.  That probably accounts for the changes found in this study.”

Go for the burn

What is probably much more important in overall weight gain or loss is how many calories a person consumes, Dr. Burant says.

“It’s all a balance in terms of calories,” Dr. Burant adds, noting that most people tend to lose weight when they reduce the amount of calories eaten, regardless of what items put in their mouths.

In other words, you can nosh on lettuce or cupcakes – as long as you carefully measure how much you’re eating to keep the caloric intake below the level your body needs or the energy you generally burn.

“Overall, there’s not a lot of evidence that one diet works better than another in the short or long term,” Dr. Burant says. The important thing is to look at all weight loss claims with a critical eye.  ‘If they seem too good to be true, they are exactly that…too good to be true.”    

As director of the Michigan Metabolomics and Obesity Center, Dr. Burant works with a group of talented obesity-related researchers on the University of Michigan campus, whose goal it is to find preventions and better treatments for diseases such as obesity, type 2 diabetes and related metabolic disorders.

Dr. Burant, the Robert C. and Veronica Atkins Professor of Metabolism, earned his medical degree and doctorate of philosophy in molecular and cellular biology from the Medical University of South Carolina in Charleston. His internship and residency were served at the University of California, San Francisco, and he completed his fellowship in the Department of Medicine, Endocrinology Section at the University of Chicago. He joined the University of Michigan faculty in 1999.


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