This article has been adapted and condensed for this newsletter from a superb article by Marni Jameson which originally appeared in the LA Times.
Fat was once the devil. Now more nutritionists are pointing accusingly at sugar and refined grains.
Most people can count calories. Many have a clue about where fat lurks in their diets. However, fewer give carbohydrates much thought, or know why they should.
But a growing number of top nutritional scientists blame excessive carbs — not fat — for America’s ills. They say cutting carbs is the key to reversing obesity, heart disease, Type 2 diabetes and hypertension.
“Fat is not the problem,” says Dr. Walter Willett, chairman of the department of nutrition at the Harvard School of Public Health. “If Americans could eliminate sugary beverages, potatoes, white bread, pasta, white rice and sugary snacks, we would wipe out almost all the problems we have with weight and diabetes and other metabolic diseases.”
It’s a confusing message. For years we’ve been fed the line that eating fat would make us fat and lead to chronic illnesses. “Dietary fat used to be public enemy No. 1,” says Dr. Edward Saltzman, associate professor of nutrition and medicine at Tufts University. “Now a growing and convincing body of science is pointing the finger at carbs, especially those containing refined flour and sugar.”
Consumption of carbohydrates has increased over the years with the help of a 30-year-old, government-mandated message to cut fat. And the nation’s levels of obesity, Type 2 diabetes and heart disease have risen.
“The country’s big low-fat message backfired,” says Dr. Frank Hu, professor of nutrition and epidemiology at the Harvard School of Public Health. “The overemphasis on reducing fat caused the consumption of carbohydrates and sugar in our diets to soar. That shift may be linked to the biggest health problems in America today.
“(O)ver time, as our bodies get tired of processing high loads of carbs, which evolution didn’t prepare us for … how the body responds to (carbohydrates) can change,” says Dr. Stephen Phinney, a nutritional biochemist and an emeritus professor of UC Davis who has studied carbohydrates for 30 years.
When cells become more resistant to those insulin instructions, the pancreas needs to make more insulin to push the same amount of glucose into cells. As people become insulin resistant, carbs become a bigger challenge for the body. When the pancreas gets exhausted and can’t produce enough insulin to keep up with the glucose in the blood, diabetes develops.
In a 12-week study published in 2008, Phinney and his colleagues put 40 overweight or obese men and women with metabolic syndrome on a 1,500-calorie diet. Half went on a low-fat, high-carb diet. The others went on a low-carb, high-fat diet. The low-fat group consumed 12 grams of saturated fat a day out of a total of 40 grams of fat, while the low-carb group ate 36 grams of saturated fat a day — three times more — out of a total of 100 grams of fat.
Despite all the extra saturated fat the low-carb group was getting, at the end of the 12 weeks, levels of triglycerides (which are risk factors for heart disease) had dropped by 50% in this group. Levels of good HDL cholesterol increased by 15%.
In the low-fat, high-carb group, triglycerides dropped only 20% and there was no change in HDL.
The take-home message from this study and others like it is that — contrary to what many expect — dietary fat intake is not directly related to blood fat. Rather, the amount of carbohydrates in the diet appears to be a potent contributor.
“The good news,” adds Willett, “is that based on what we know, almost everyone can avoid Type 2 diabetes. Avoiding unhealthy carbohydrates is an important part of that solution.” For those who are newly diagnosed, he adds, a low-carb diet can take the load off the pancreas before it gets too damaged and improve the condition — reducing or averting the need for insulin or other diabetes meds.
Americans can also blame high-carb diets for why the population has gotten fatter over the last 30 years, says Phinney, who is co-author of “The New Atkins for a New You” (Simon & Schuster, 2010).
“Carbohydrates are a metabolic bully,” Phinney says. “They cut in front of fat as a fuel source and insist on being burned first. What isn’t burned gets stored as fat, and doesn’t come out of storage as long as carbs are available. And in the average American diet, they always are.”
“At my obesity clinic, my default diet for treating obesity, Type 2 diabetes and metabolic syndrome is a low-carb diet,” says Dr. Eric Westman, director of the Lifestyle Medicine Clinic at Duke University Medical Center. “If you take carbohydrates away, all these things get better.”
As nutrition scientists try to find the ideal for the future, others look to history and evolution for answers. One way to put our diet in perspective is to imagine the face of a clock with 24 hours on it. Each hour represents 100,000 years that humans have been on the Earth.
On this clock, the advent of agriculture and refined grains would have appeared at about 11:54 p.m. (23 hours and 54 minutes into the day). Before that, humans were hunters and gatherers, eating animals and plants off the land. Agriculture allowed for the mass production of crops such as wheat and corn, and refineries transformed whole grains into refined flour and created processed sugar.
Some, like Phinney, would argue that we haven’t evolved to adapt to a diet of refined foods and mass agriculture — and that maybe we shouldn’t try.
