Presenting results of a meta-analysis comparing low-carbohydrate and low-fat diets is never uneventful when the nation is weeks away from adopting the 2015 Dietary Guidelines for Americans.
Most of Tuesday’s presentation at the Four Seasons Hotel in New York City was quite pleasant. Cardiologist and former FDA official Jonathan Sackner-Bernstein, MD, presented results from a meta-analysis published that day in the journal PloS ONE, which found low-carbohydrate diets produced more weight loss and less cardiovascular risk than low-fat diets, although both were better than doing nothing if you’re overweight.
For more than an hour, Sackner-Bernstein held a measured discussion with 3 panelists—nutrition and weight management expert Samuel Klein, MD; Ronald M. Krauss, MD, who studies the effects of genetics, diet, and pharmacology on lipid metabolism; and Jeff Volek, PhD, RD, an expert on low-carbohydrate diets as well as the management of insulin resistance in type 2 diabetes (T2D). CNN host Lisa Ling served as the moderator.
Results had come from 17 clinical trials involving 1797 patients. According to the study, the likelihood that the low carbohydrate diet would result in more weight loss than a low-fat diet was 99%, by a difference of 2.0 kg. The likelihood that the low-carb diet would favor risk reduction was 98%. As Sackner-Bernstein said, when it comes to a low carbohydrate diet, “For most people, this is better.”
Studies involving those with comorbidities did not meet the criteria for the meta-analysis, but given what is known about insulin resistance, Sackner-Bernstein and Volek agreed it could be assumed that a person with T2D would respond even better to a low-carbohydrate diet.
Then, at the end, came the question: For those who’ve been following the 2015 Dietary Guidelines for Americans—the effort every 5 years to update the nation’s nutrition policy—what should they recommend?
“There probably need to be multiple recommendations,” said Volek, who called for flexibility to recognize the varying health status among Americans. “No one size fits all.”
OK, that’s reasonable. But after adding “there is no perfect fit,” Krauss started criticizing the entire process, calling the effort to develop guidelines a “fool’s errand.”
Welcome to the hornet’s nest that is the 2015 Dietary Guidelines.
At this point it would be fair to mention that the session and the study were sponsored by Atkins Nutritionals, and the last question came from Nina Teicholz, author of The Big Fat Surprise, whose critique of the report from the 2015 Dietary Guidelines Advisory Committee (DGAC) in BMJ is perhaps the seminal event in the effort to upend the guidelines.
The BMJ article, which was picked up in some media outlets and blasted in others (BMJ issued a clarification), hit just ahead of an October 7, 2015, hearing before Congress with Secretaries Tom Vilsack of the Department of Agriculture (USDA) and Sylvia Mathews Burwell of HHS, who oversee the process.
The effort to write the guidelines is inherently political, but the 2015 DGAC members feel this go-round has brought a new level of gamesmanship. Already HHS and USDA have abandoned the panel’s recommendation that the 2015 guidelines take sustainability of the food supply into account. DGAC's report was issued in February and the final guidelines are due by the end of the year.
The big concern is DGAC’s recommendation that Americans limit consumption of red and processed meat. Lean meat, however, was considered part of a healthy diet, and the panel lifted the longtime recommendation against cholesterol for most people (those whose health conditions require limitations should follow their doctors’ advice). Critics say that despite these changes and more focus on plant-based foods, there is still too much emphasis on carbohydrates. Thus, the DGAC report is being blasted by both the beef industry and the Sugar Association over a separate recommendation for daily added sugar limits.
That’s not to say that the Dietary Guidelines have not had flaws over the decades. In an interview with Evidence-Based Diabetes Management last month, Osama Hamdy, MD, PhD, of the Joslin Diabetes Center said the old food pyramid that once dominated nutritional thinking did a lot of damage. But Hamdy said de-emphasizing carbs doesn’t mean a diet with lots of bacon or saturated fats is a great idea, either. The Why WAIT diet he developed for a weight-loss intervention limited saturated fat to 10% of the diet and carbohydrates to 40%. (Evidence-Based Diabetes Management is a publication of The American Journal of Managed Care.)
In 2011, nutrition policy made a significant change at the consumer level with “My Plate,” which puts less emphasis on carbohydrates; recommendations that had emphasized multiple servings of breads and cereals now said “make half your plate fruits and vegetables.” On a parallel track, the FDA has been moving toward new food labels that do more to highlight added sugars, in response to criticisms that Americans backfilled fats with sugar to replace the calories.
Dietary Guidelines have a significant effect on the Supplemental Nutritional Assistance Program (SNAP). Since 2009, and especially since the 2010 Guidelines, USDA has made it easier to use the program at farmers’ markets, to give users greater access to fresh food. As a result, the number of markets rose from about 5200 to more than 8500.
Study Details. Trials evaluated in the PLoS ONE study took an average of 26 weeks. Patients were 44 years old on average, with an average body mass index of 34. Most were women (77%). Low fat diets were defined as ≤30% of calories from fat per day; and low carbohydrate diets were defined as 120 gm per day or less.
Most of the session Tuesday brought strong questions and observations from the group, which was largely registered dieticians—Klein called them the “infantry” in America’s battle with obesity, who unfortunately do not enjoy the reimbursement status of physicians. Will we see biomarkers to guide dietary planning, they asked? Probably not, Volek said. One dietician said it was no secret why carbohydrates dominate—they’re cheap. Another said she concentrates on portion control, which was the focus of former Mayor Michael Bloomberg’s campaign against oversized sodas.
For all the controversy with the guidelines themselves, Tuesday’s study is benign.
“All this study says is that reducing calories, either by lowering carbohydrate or lowering fat, enables people to lose weight. The studies in this meta-analysis show that people lost somewhat more weight on low-carbohydrate diets,” said Marion Nestle, PhD, MPH, of New York University, author of the blog Food Politics. “The bottom line: calories count, but fat is likely to be more satiating. This is not news, but it is very much in the interest of Atkins Nutritionals—and of investigators interested in getting the dietary guidelines to say less about fat—to demonstrate that higher fat diets are healthy.”
As for whether creating guidelines is a “fool’s errand,” earlier this month Burwell asked the members of Congress to consider what school lunches, military meals, and the SNAP allotment might look like if there were no rules at all.
“We are on the wrong trajectory,” she said, “but would the trajectory have been worse?”
Sackner-Bernstein J, Kanter D, Kaul S. Dietary intervention for overweight and obese adults: comparison of low-carbohydrate and low-fat diets. A meta-analysis. PloS ONE. 2015;10(10):e0139817. doi:10.1371/journal.pone.0139817.